1  OrthorhojTibic,  p  <  v 


2  Monoclinic  -Tnclin.ed  Dispersion  . 


3  Monoclinic  -  Horizontal   Dispersion 


:-, 


Monoclinic  —  Crossed  DispersioiL 


A  TEXT-BOOK 


OF 


,  MI NE  RAL  0  G Y 


WITH   AN   EXTENDED   TREATISE   ON 


CRYSTALLOGRAPHY  AND  PHYSICAL  MINERALOGY. 


BY 


EDWARD  SALISBUEY  DANA, 

CURATOR  OF  MINERALOGY,  YALE  COLLEGE. 
ON  THE  PLAN  AND  WITH  THE  CO-OPERATION 


OF 


PROFESSOR    JAMES  D.  DANA. 


WITH     UPWARDS     OF     EIGHT     HUNDRED     WOODCUTS     AND     ONE    COLORED    PLATE. 


NEW   YORK: 

JOHN    WILEY    &    SONS, 

15  ASTOR  PLACE. 

1877. 


COPYRIGHT  BY 
EDWAKD    S.    DANA, 

1877. 


JOHN  F.  TROW  &  SON. 

PRIMTEKS  AND  STEREOTYVERS, 

205-213  Rast  Tztk  St., 

NEW    YORK. 


PREFACE. 


THE  preparation  of  a  "Text-Book  of  Mineralogy"  was  undertaken  in 
1868,  by  Prof.  J.  D.  Dana,  immediately  after  the  publication  of  the  fifth 
edition  of  the  System  of  Mineralogy.  The  state  of  his  health,  however, 
early  compelled  him  to  relinquish  the  work,  and  he  was  not  able  subsequently 
to  resume  it.  Finally,  after  the  lapse  of  seven  years,  the  editorship  of  the 
volume  was  placed  in  the  hands  of  the  writer,  who  has  endeavored  to  carry 
out  the  original  plan. 

The  work  is  intended  to  meet  the  requirements  of  class  instruction.  With 
this  end  in  view  the  Descriptive  part  has  been  made  subordinate  to  the 
more  important  subjects  embraced  under  Physical  Mineralogy. 

The  Crystallography  is  presented  after  the  methods  of  ISTaumann ;  his 
system  being  most  easily  understood  by  the  beginner,  and  most  convenient 
for  giving  a  general  knowledge  of  the  principles  of  the  Science.  For  use 
in  calculations,  however,  it  is  much  less  satisfactory  than  the  method  of 
Miller,  and  a  concise  exposition  of  Miller's  System  has  accordingly  been 
added  in  the  Appendix.  The  chapter  on  the  Physical  Characters  of  Min- 
erals has  been  expanded  to  a  considerable  length,  but  not  more  than  was 
absolutely  necessary  in  order  to  make  clearly  intelligible  the  methods  of 
using  the  principles  in  the  practical  study  of  crystals.  For  a  still  fuller 
discussion  of  these  subjects  reference  may  be  made  to  the  works  of  Schrauf 
and  of  Groth,  and  for  details  in  regard  to  the  optical  characters  of  mineral 
species  to  the  Mineralogy  of  M.  DesCloizeaux. 

The  Descriptive  part  of  the  volume  is  an  abridgment  of  the  System  of 
Mineralogy,  and  to  that  work  the  student  is  referred  for  the  history  of  each 
species  and  a  complete  list  of  its  synonyms ;  for  an  enumeration  of  ob- 
served crystalline  planes,  and  their  angles ;  for  all  published  analyses ; 

260498 


IV  PREFACE. 

for  a  fuller  description  of  localities  and  methods  of  occurrence,  and  also  for 
an  account  of  many  species  of  uncertain  character,  not  mentioned  in  the 
following  pages.  A  considerable  number  of  changes  and  additions,  how- 
ever, have  been  made  in  the  preparation  of  the  present  work,  made*  neces- 
sary by  the  progress  in  the  Science,  and  among  these  are  included  many 
new  species.  The  chemical  formulas  are  those  of  modern  Chemistry.  The 
new  edition  of  Rammelsberg's  Handbuch  der  Mineralchemie  has  been 
often  used  in  the  preparation  of  the  volume,  and  frequent  references  to  him 
will  be  found  in  the  text. 

The  work  has  throughout  been  under  the  supervision  of  Prof.  Dana,  and 
all  the  proofs  have  passed  under  his  eye.  Acknowledgments  are  also  due 
to  Prof.  G-.  J.  Brush  and  Prof.  J.  P.  Oooke  for  friendly  advice  on  many 
points. 

NEW  HAVEN,  March  1st,  1877. 


TABLE    OF    CONTENTS. 


INTRODUCTION. 

IP  A.  R,  T     I. 

PHYSICAL  MINERALOGY. 
Section  I.     CRYSTALLOGRAPHY. 

PAGE 

DESCRIPTIVE  CRYSTALLOGRAPHY 1-83 

General  Characters  of  Crystals 1 

Descriptions  of  some  of  the  Simpler  Forms  of  Crystals 3 

Systems  of  Crystallization 8 

Laws  with  reference  to  the  Planes  of  Crystals 10 

I.  Isometric  System 14 

II.   Tetragonal  System 25 

III.  Hexagonal  System. 31 

IV.  Orthorhombic  System 41 

V.   Monoclinic  System 47 

VI.   Triclinic  System 50 

MATHEMATICAL  CRYSTALLOGRAPHY , 51 

Methods  of  Calculation  in  General 53 

Special  Methods  of  Calculation  in  the  different  Systems 62 

Measurement  of  the  Angles  of  Crystals 83 

COMPOUND  OR  TWIN  CRYSTALS 88 

IRREGULARITIES  OF  CRYSTALS 102 

CRYSTALLINE  AGGREGATES Ill 

PSEUDOMORPHOUS  CRYSTALS 113 

Section  II.     PHYSICAL  CHARACTERS  OF  MINERALS. 

I.  COHESION  AND  ELASTICITY 115 

Cleavage  and  Fracture 115 

Hardness ( 116 

Tenacity 117 

II.  SPECIFIC  GRAVITY 119 

III.  LIGHT "  .  121 

Fundamental  Principles  of  Optics 121 

Distinguishing1  Optical  Characters  of  Crystals  of  the  different  Systems. 131 

Isometric  Crystals 131 

Uuiaxial  Crystals 132 

Biaxial  Crystals 140 

Diaphaneity ;   Color .- 157 

Lustre 163 

IV.  HEAT 164 

V.  ELECTRICITY — MAGNETISM 165 

VI.  TASTE  AND  ODOR..  .  167 


VI  TABLE    OF   CONTENTS. 

D?  A.  R  T    II. 

CHEMICAL  MINERALOGY. 

PAGE 

Chemical  Constitution  of  Minerals 169 

Dimorphism  ;    Isomorphism 177 

Chemical  Examination  of  Minerals  : 

In  the  Wet  Way 180 

In  the  Dry  Way  :  Blowpipe  Analysis 181 

!>  A.  R  T    I  II. 

DESCRIPTIVE  MINERALOGY. 

Classification  of  Mineral  Species 193 

Description  of  Mineral  Species 199-397 

APPENDIX  A.  Miller's  System  of  Crystallography 399 

APPENDIX  B.  On  the  Drawing  of  Figures  of  Crystals 421 

APPENDIX  C.   Tables  for  use  in  the  Determination  of  Minerals 431 

APPENDIX  D.  Catalogue  of  American  Localities  of  Minerals 447 

GENERAL  INDEX.  . .  .  477 


INTRODUCTION. 


THE  Third  Kingdom  of  Nature,  the  Inorganic,  embraces  all  species  not 
organized  by  living  growth.  Unlike  a  plant  or  animal,  an  inorganic  spe- 
cies is  a  simple  chemical  compound,  possessing  unity  of  chemical  and  physi- 
cal nature  throughout,  and  alike  in  essential  characters  through  all  diversity 
of  age  or  size. 

The  Science  of  Mineralogy  treats  of  those  inorganic  species  which  occur 
ready  formed  in  or  about  the  earth.  It  is  therefore  but  a  fragment  of  the 
Science  of  Inorganic  nature,  and  it  owes  its  separate  consideration  simply 
to  convenience. 

The  Inorganic  Compounds  are  formed  by  the  same  forces,  and  on  the  same  principles, 
whether  produced  in  the  laboratory  of  the  chemist  or  in  outdoor  nature,  and  are  strictly  no 
more  artificial  in  one  case  than  in  the  other.  Calcium  carbonate  of  the  chemical  laboratory 
is  in  every  character  the  same  identical  substance  with  calcium  carbonate,  or  calcite,  found 
in  the  rocks,  and  in  each  case  is  evolved  by  nature's  operations.  There  is  hence  nothing 
whatever  in  the  character  of  mineral  species  that  entitles  them  to  constitute  a  separate 
division  in  the  natural  classification  of  Inorganic  species. 

The  objects  of  Mineralogy  proper  are  three-fold  :  1,  to  present  the  true 
idea  of  each  species  ;  2,  to  exhibit  the  means  and  methods  of  distinguishing 
species,  which  object  is  however  partly  accomplished  in  the  former  ;  3,  to 
make  known  the  modes  of  occurrence  and  associations  of  species,  and  their 
geographical  distribution. 

In  presenting  the  science  in  this  Text  Book,  the  following  order  is 
adopted  : 

I.  PHYSICAL  MINERALOGY,  comprising  that  elementary  discussion   with 
regard  to  the  structure  and  form,  and  the  physical  qualities  essential  to  a 
right  understanding  of  mineral  species,  and  their  distinctions. 

II.  CHEMICAL  'AND   DETERMINATIVE  MINERALOGY,  presenting  briefly  the 
general  characters  of  species  considered  as  chemical  compounds,  also  giving 
the  special  methods  of  distinguishing  species,  and  tables  constructed  for  this 
purpose.     The  latter  subject  is  preceded  by  a  few  words  on  the  use  of  the 
blow-pipe. 

III.  DESCRIPTIVE  MINERALOGY,  comprising  the  classification  and  descrip- 
tions of  species  and  their  varieties.     The  descriptions  include  the  physical 
and  chemical  properties  of  the  most  common  and  important  of  the  minerals. 


VI 11  INTRODUCTION. 

with  some  account  also  of  their  association  and  geographical  distribution. 
The  rarer  species,  and  those  of  uncertain  composition,  are  only  very  briefly 
noticed. 

Besides  the  above,  there  is  also  the  department  of  Economic  Mineralogy,  which  is  not  here 
included.  It  treats  of  the  uses  of  minerals,  (1)  as  ores ;  (2)  in  jewelry  ;  and  (3)  in  the  coarser 
arts. 

The  following  subjects  connected  with  minerals  properly  pertain  to  Geology  :  1,  LiiJwlo- 
gical  geology,  or  Lithotogy,  which  treats  of  minerals  as  constituents  of  rocks.  2,  Chemical 
geology,  which  considers  in  one  of  its  subdivisions  the  origin  of  minerals,  as  determined,  in 
the  light  of  chemistry,  by  the  associations  of  species,  the  alterations  which  species  are  liable 
to,  or  which  they  are  known  to  have  undergone,  and  the  general  nature,  origin,  and  changes 
of  the  earth's  rock  formations.  Under  chemical  geology,  the  department  which  considers 
especially  the  associations  of  species,  and  the  order  of  succession  in  such  associations,  has 
received  the  special  name  of  the  paragenesis  of  minerals  ;  while  the  origin  of  minerals  or 
rocks  through  alteration,  is  called  metamorphism  or  pseudomorphism,  the  latter  term  being 
restricted  to  those  cases  in  which  the  crystalline  form,  and  sometimes  also  the  cleavage,  of 
a  mineral  is  retained  after  the  change. 


For  a  catalogue  of  mineralogical  works,  and  of  periodicals,  and  transactions  of  Scientific 
Societies  in  which  mineralogical  memoirs  have  been  and  are  published,  reference  is  made  to 
the  System  of  Mineralogy  (1868),  pp.  xxxv-xlv.,  and  Appendix  II.  (1874).  The  following- 
works,  however,  deserve  to  be  mentioned  as  will  be  found  useful  as  books  of  reference. 

In  CRYSTALLOGRAPHY  : 

Naumann.  Lehrbuch  der  reinen  und  angewandten  Krystallographie.  2  vols. ,  8vo. 
Leipzig,  1829. 

Naumann.  Anfangsgriinde  der  Krystallographie.     2d  ed.,  292  pp.,  8vo.     Leipzig,  1854. 

Naumann.  Elemente  der  theoretischen  Krystallographie.     883  pp.,  8vo.     Leipzig,  1856. 

Miller.   A  Treatise  on  Crystallography.     Cambridge,  1839. 

Grailich.  Lehrbuch  der  Krystallographie  von  W.  H.  Miller.     328  pp.,  8vo.     Vienna,  1856. 

Kopp.   Einleitung  in  die  Krystallographie.     348  pp.,  8vo.     Braunschweig,  1862. 

Von  Lang.  Lehrbuch  der  Krystallographie.     358  pp.,  8vo.     Vienna,  1866. 

Quenstedt.   Grundriss  der  bestimmeiiden  und  rechnenden  Krystallographie.   Tubingen,  1873. 

Rose-Sadebeck.  Elemente  der  Krystallographie.  3d  ed.,  vol.  i.,  181  pp.,  8vo.  Berlin, 
1873.  Vol.  ii.,  Angewandte  Krystallographie.  284  pp.,  8vo.  Berlin,  1876. 

ScJirauf.  Lehrbuch  der  Physikalischen  Mineralogie.  Vol.  i.,  Krystallographie.  251  pp., 
8vo.,  1866;  vol.  ii.,  Die  angewandte  Physik  der  Krystalle.  426  pp.  Vienna,  1868. 

Groth.  Physikalische  Krystallographie.     527  pp. "  8vo.     Leipzig,  1876. 

Klein.  Einleitung  in  die  Krystallberechnung.     393  pp.,  8vo.     Stuttgart,  1876. 

In  PHYSICAL  MINERALOGY  the  works  of  Schrauf  (1868) ,  and  Groth  (1876),  titles  as  in  the 
above  list.  Reference  is  also  made  to  the  works  on  Physics  mentioned  on  p.  156.  In  addi- 
tion to  these,  on  pp.  Ill,  118,  156,  163,  167  a  few  memoirs  of  especial  importance  on  the 
different  subjects  are  enumerated. 

In  CHEMICAL  MINERALOGY  :  Rammelsberg ,  Handbuch  der  Miner  alchemic,  2d  ed. ,  Leipzig, 
1875.  In  Determinative  Mineralogy,  Brush  (New  York,  1875). 

'In  DESCRIPTIVE  MINERALOGY  :  among  recent  works  those  of  Brooke  and  Miller  (2d  ed.  of 
Phillips'  Min.),  London,  1852  ;  Quenatedt,  2d  ed.,  Tubingen,  1863;  Schrauf,  Atlas  der  Krys- 
tallformen.  Lief.  I. -IV.,  1871-1873  ;  Kokscharof,  Materialien  zur  Mineralogie  Russlands, 
vol.  i. ,  1865,  vol.  vi.,  1874  ;  DesCIoizeaux,  vol.  i.,  1862,  vol.  ii.,  Paris,  1874;  Dana,  System  of 
Mineralogy,  1868,  App.  I.,  1872,  App.  II.;  1874 ;  Blum,  4th ed.,  1874  ;  Naunann,  9th  ed.,  1874. 

The  following  publications  are  devoted  particularly  to  Mineralogy  : 

Jahrbuch  fur  Mineralogie  ;  G.  Leonhard  and  H.  B.  Geinitz  Editors,  Stuttgart. 

Tschermak  Mineralogische  Mittheilungen  ;  G.  Tschermak  Editor,  Vienna. 

Mineralogical  Magazine  and  Journal  of  the  Mineralogical  Society  ;  London,  and  Truro, 
Cornwall.  Commenced  1875. 

Zeitschrift  fur  Krystallographie  ;  P.  Groth  Editor  ;  Leipzig.     Commenced  1876. 


ABBREVIATIONS  EMPLOYED  IN  THE  DESCRIPTION  OF  SPECIES. 


B.B.  Before  the  Blowpipe  (p.  188).  Obs.          Observations  on  occurrence,  etc. 

Comp.  Composition.  O.F.  Oxidizing  Flame  (p.  182). 

Diff.  Differences,  or  distinctive  characters.  Pyr.          Pyrognostics. 

G.  Specific  Gravity.  Q.  Ratio.  Quantivalent  Ratio  (p.  176). 

Germ.  German.  R.F.  Reducing  Flame  (p.  182). 

H.  Hardness.  Var.          Varieties. 


I. 

PHYSICAL    MINERALOGY 


THE  grand  departments  of  the  science  here  considered  are  the  following : 
1.  STRUCTURE. — Structure  in  Inorganic  nature  is  a  result  of  mathemati- 
cal symmetry  in  the  action  of  cohesive  attraction.  The  forms  produced 
are  regular  solids  called  crystals  ;  whence  morphology  is,  in  the  Inorganic 
kingdom,  called  CRYSTALLOLOGY.  It  is  the  science  of  structure  in  this  king- 
dom of  nature. 

2.  PHYSICAL  PROPERTIES  OF  MINERALS,  or  those  depending  on  relations  to 
light,  heat,  electricity,  magnetism  ;  on  differences  as  to  density  or  specific 
gravity,  hardness,  taste,  odor,  etc. 

Crystall  ology  is  naturally  divided  into,  I.  CRYSTALLOGRAPHY,  which  treats 
of  the  forms  resulting  from  crystallization ;  II.  CRYSTALLOGENY,  which  de- 
scribes the  methods  of  making  crystals,  and  discusses  the  theories  of  their 
origin.  Only  the  former  of  these  two  subjects  is  treated  of  in  this  work. 


SECTION  I. 
CRYSTALLOGRAPHY. 

Crystallography  embraces  the  consideration  of — (1)  normally  formed  or 
regular  crystals ;  (2)  twin  or  compound  crystals  ;  (3)  the  irregularities  of 
crystals  ;  (4)  crystalline  aggregates  ;  and  (5)  pseudomorphous  crystals. 

1.  GENERAL  CHARACTERS  OF  CRYSTALS. 

(1)  External  form. — Crystals  are  bounded  by  plane  surfaces, 
called  simply  planes  or  faces,  symmetrically  arranged  in  refer- 
ence to  one  or  more  diametral  lines  called"  axes.     In  the  an- 
nexed figure  the  planes  1  and  the  planes  i  are  symmetrically 
arranged  with  reference  to  the  vertical  axis  c  c  ;  and  also  the 
planes  of  each  kind  with  reference  to  the  three  transverse  axes. 

(2)  Constancy  of  angle  in  the  same  species. — The  crystals  of 
any  species  are  essentially  constant  in  the  angle  of  inclination 
between  like  planes.     The  angle  between  1  and  ?',  in  a  given 

species,  is  always  essentially  the  same,  wherever  the  crystal  is  found,  and 
whether  a  product  of  nature  or  of  the  laboratory. 


CRYSTALLOGRAPHY. 


(3)  Difference  of  angle  of  different  species. — The  crystals  of  different 
species  commonly  differ  in   angles  between  corresponding  planes.     The 
angles  of  crystals  are  consequently  a  means  of  distinguishing  species. 

(4)  Diversity  of  planes. — While  in  the  crystals  of  a  given  species  there 
is  constancy  of  angle  between  like  planes,  the  forms  of  the  crystals  may  be 
exceedingly  diverse.     The  accompanying  figures  are  examples  of  a  few  of 


the  forms  of  the  species  zircon.  There  is  hardly  any  limit  to  the  number  of 
forms  which  may  occur  ;  yet  for  each  the  angles  "bet  ween  like  planes  are 
essentially  constant. 

Crystals  occur  of  all  sizes,  from  the  merest  microscopic  point  to  a  yard  or  more  in  diame- 
ter. A  single  crystal  of  quartz,  now  at  Milan,  is  three  and  a  quarter  feet  long1,  and  five  and  a 
half  in  circumference  ;  and  its  weight  is  estimated  at  eight  hundred  and  seventy  pounds. 
A  single  cavity  in  a  vein  of  quartz  near  the  Tiefen  Glacier,  in  Switzerland,  discovered  in 
1867,  has  afforded  smoky  quartz  crystals  weighing  in  the  aggregate  about  20,000  pounds  ;  a 
considerable  number  of  the  single  crystals  having  a  weight  of  200  to  250  pounds,  or  even 
more.  One  of  the  gigantic  beryls  from  Acworth,  New  Hampshire,  measures  four  feet  in 
length,  and  two  and  a  half  in  circumference;  and  another,  at  Graf  ton,  is  over  four  feet  long, 
and  thirty-two  inches  in  one  of  its  diameters,  and  does  not  weigh  less  than  two  and  a  half 
tons.  But  the  highest  perfection  of  form  and  transparency  are  found  only  in  crystals  of 
small  size. 

In  its  original  signification  the  term  crystal  was  applied  only  to  crystals  of  quartz  (f.  1), 
which  the  ancient  philosophers  believed  to  beicater  congealed  by  intense  cold.  Hence  the 
term,  from  KptWaAAos,  ice. 


(5)  Symmetry  in  the  position  of  planes.  —  The  planes  on  the  crystals 
of  any  species,  however  numerous,  are  arranged  in  accordance  with  certain 
laws  of  symmetry  and  numerical  ratio.  If  one  of  the  simpler  forms  be 
taken  as  a  primary  OY  fundamental  form,  all  other  planes  will  be  secondary 
planes,  or  modifications  of  the  fundamental  form.  It  should  be  observed, 
however,  that  the  forms  called  primary  and  fundamental  in  crystallographic 
description,  are  in  general  merely  so  by  assumption  and  for  convenience 
of  reference.  (See  also  p.  12.)  - 

Cleavage.  —  Besides  external  symmetry  of  form,  crystallization  produces 
also  regularity  of  internal  structure,  and  often  of  fracture.  This  regular- 
ity of  fracture,  or  tendency  to  break  or  cleave  along  certain  planes,  is  called 
cleavage.  The  surface  afforded  by  cleavage  is  often  smooth  and  brilliant. 
The  directions  of  cleavage  are  those  of  least  cohesive  force  in  a  crystal  ;  it 


CRYSTALLOGRAPHY. 


is  not  to  be  understood  that  the  cleavage  lamellae  are  in  any  sense  present 
before  they  are  made  to  appear  by  fracture. 

In  regard  to  cleavage,  two  principles  may  be  here  stated  : — (a)  In  any 
species,  the  direction  in  which  cleavage  takes  place  is  always  parallel  to 
some  plane  which  either  actually  occurs  in  the  crystals  or  may  exist  there 
in  accordance  with  the  general  laws  which  will  be  stated  hereafter. 

•(b)  Cleavage  is  uniform  as  to  ease  parallel  to  all  like  planes  ;  that  is,  if 
it  may  be  obtained  parallel  to  one  plane  of  a  kind  (as  1,  f.  1),  it  may  be  ob- 
tained with  equal  facility  parallel  to  each  of  the  other  planes  1  ;  and  will 
afford  planes  of  like  lustre.  This  is  in  accordance  with  the  symmetry  of 
crystallization.  It  will  be  evident  from  this  that  the  angles  between  planes 
of  like  cleavage  will  be  constant :  thus,  a  mass  of  calcite  under  the  blow  of 
a  hammer  will  separate  into  countless  rhombohedrons,  each  of  which  affords 
on  measurement  the  angles  74°  55'  arid  105°  5X.  In  a  shapeless  mass  of 
marble  the  minute  grains  have  the  same  regularity  of  cleavage  structure. 
See  further,  p.  115. 

2.  DESCRIPTIONS  OF  SOME  OF  THE  SIMPLER  FORMS  OF  CRYSTALS. 

PRELIMINARY  DEFINITIONS.  Angles. — In  the  descriptions  of  crystals  three 
kinds  of  angles  may  come  under  consideration,  solid,  plane,  and  inter  fa- 
cial. The  last  are  the  inclinations  between  the  faces  or  planes  of  crystals. 

Axes. — The  crystallographic  axes  are  imaginary  lines  passing  through 
the  centre  of  a  crystal.  They  are  assumed  as  axes  in  order  to  describe,  by 
reference  to  them,  the  relative  positions  of  the  different  planes.  One  of 
the  axes  is  called  the  vertical,  and  the  others  the  lateral  /  the  number  of 
lateral  axes  is  either  two  or  three.  The  axes  have  essentially  the  same  re- 
lative lengths  in  all  the  crystals  of  a  species ;  but  those  of  different  species 
often  differ  widely 

Diametral  planes. — The  planes  in  which  any  two  axes  lie  are  called  the 
axial  or  diametral  planes  or  sections ;  they  are  the  coordinate  planes  of  an- 
alytical geometry.  They  divide  the  space  about  the  centre  into  sectants' 
into  eight  sectants,  called  octants,  if  there  are  but  two  lateral  axes,  as  is 
generally  the  case  ;  but  into  twelve  sectants  if  there  are  three,  as  in  hexa- 
gonal crystalline  forms. 

Diagonal  planes  are  either  diagonal  to  the  three  axes,  as  those  through 
the  centre  connecting  diagonally  opposite  solid  angles  of  a  cube,  01  diag- 
onal to  two  axes,  and  passing  through  the  third,  as  those  connecting  diag- 
onally opposite  edges  of  the  cube. 

Similar  planes  and  edges  are  such  as  are  similar  in  position,  and  of  like 
angles  with  reference  to  the  axes  or  axial  planes.  Moreover,  in  the  case  of 
similar  edges,  the  two  planes  by  whose  intersection  the  edges  are  formed, 
meet  at  the  same  angle  of  inclination.  For  example,  all  the  planes  and 
edges  of  the  tetrahedron  (f.  9),  regular  octahedron  (f.  11),  cube  (f.  14), 
rhombic  dodecahedron  (f.  19),  are  similar.  In  the  rhombohedron  (f.  16) 
there  are  two  sets  of  similar  edges,  six  being  obtuse  and  six  acute. 

Solid  angles  are  similar  when  alike  in  plane  angles  each  for  each,  and 
when  formed  by  the  meeting  of  planes  of  the  same  kind. 

A  combination-edge  is  the  edge  formed  by  the  meeting  or  intersection  of 
two  planes. 


CRYSTALLOGRAPHY. 


Truncations,  Revetments.  —  In  a  crystal,  an  edge  or  angle  is  said  to  be  re- 
placed when  the  place  of  the  edge  or  angle  is  occupied  by  one  or  more 
planes  ;  and  in  the  case  of  the  replacement  of  an  edge,  the  replacing 
planes  make  parallel  intersections  with  the  including  planes,  that  is,  with 
the  direction  of  the  replaced  edge  (f.  43). 

A  replacement  of  an  edge  or  angle  is  a  truncation  when  the  replacing 
plane  makes  equal  angles  with  the  including  planes.  Thus,  in  f.  6,  i-i 
truncates  the  edge  between  I  and  /. 

An  edge  is  said  to  be  bevelled  when  it  is  replaced  by  two  similar  planes, 
that  is,  by  planes  having  like  inclinations  to  the  adjoining  planes.  Thus, 
in  f.  5,  the  edge  between  3,  3,  is  bevelled  by  the  two  planes  3-3,  3-3,  the  right 
3-3  and  3  having  the  same  mutual  inclination  as  the  left  3-3  and  3.  So, 
in  f.  192,  p.  43,  the  edge  between  /and  /is  bevelled  by  the  planes  i-2,  i-2. 
Truncations  and  bevelments  of  edges  take  place  only  between  similar 
planes.  Thus  /,  /,  and  3,  3,  are  similar  planes  in  fig.  5.  The  edge  i|i  might 
be  truncated  or  bevelled,  for  the  same  reason  ;  but  not  the  edge  between  1 
and  /,  since  1  and  /  are  dissimilar  planes. 

A  zone  is  a  series  of  planes  in  which  the  combination-edges  or  mutual 
•intersections  are  parallel.  Thus,  in  fig.  3,  the  planes  1,  3,  /make  a  vertical 
zone  ;  so  in  f  .  8,  the  planes  between  1  and  i-i  make  a  zone,  and  this  zone 
actually  continues  above  and  below,  around  the  crystal  ;  in  f.  5,  the  planes 
3,  3-3,  3-3,  3  are  in  one  zone  ;  and  i-i,  /,  i-i,  /,  in  another.  On  the  true 
meaning  of  zones,  see  p.  53. 

The  above  explanations  are  preliminary  to  the  descriptions  of  the  forms 
of  all  crystals. 

A.  —  FORMS   CONTAINED  UNDER  FOUR 

EQUAL    TRIANGULAR     PLANES.  -  A.  Regu- 

lar tetrahedron  (f.  9).  Edges  six  ;  solid 
angles  four.  Faces  equilateral  trian- 
gles, and  plane  angles  therefore  60°. 
Interfacial  angles  70°  31'  44".  Named 
from  TerpaKis,  four  times,  and  eSpa, 
face. 
2.  Sphenoid  (f.  10).  Faces  isosceles  triangles,  not  equilateral.  Plane  and 

interfacial  angles  varying  ;  the  latter  of  two  kinds,  (a)  two  terminal,  (b)  four 

lateral.     Named  from  o-Qtfv,  a  wedge. 


B.  —  FORMS  CONTAINED  UNDER  EIGHT  TRIANGULAR  PLANES.  —  The  solids 
here  included  are  called  octahedrons,  from  oKTatcis,  eight  times,  and  eSpa, 
face.  They  have  twelve  edges  ;  and  six  solid  angles.  One  of  the  axes, 
'when  they  differ  in  length,  is  made  the  vertical  axis  ;  and  the  others  are 
the  lateral  axes.  The  solid  angles  at  the  extremities  of  the  vertical  axes  are 
the  vertical  or  terminal  solid  angles  ;  the  other  four  are  the  lateral.  The 
four  edges  meeting  in  the  apex  of  the  terminal  solid  angle  are  the  terminal 
edges  ;  the  others,  the  lateral  of  basal  edges. 

1.  Regular  Octahedron  (f.  11).  Faces  equilateral  triangles.  Interfacial 
angles  109°  28'  16"  ;  angle  between  the  planes  over  the  apex  of  a  solid 
angle  70°  31'  44"  ;  angle  between  edges  over  a  solid  angle  90°.  The  three 
axes  are  equal,  and  hence  either  may  be  made  the  vertical.  Lines  connect- 
ing the  centres  of  opposite  faces  are  called  the  octahedral  or  trigonal  inter- 


CRYSTALLOGRAPHY. 


axes  ;  and  those  connecting  the  centres  of  opposite  edges  the  dodecahedral 
or  rhombic  interaxes. 

2.  Square  Octahedron  (f.  12,  f.  12A).  Faces  equal  isosceles  triangles, 
not  equilateral.  The  four  terminal  edges  are  equal  and  similar ;  and  so 
also  the  four  lateral. 


11 


12 


12A 


The  lateral  axes  are  equal ;  the  vertical  axis  may  be  longer  or  shorter 
than  the  lateral. 

3.  The  rhombic  octahedron  (f.  13)  differs  from  the  square  octahedron  in 
having  a  rhombic  base,  and  consequently  the  three  axes  are  unequal.  The 
basal  edges  are  equal  and  similar  ;  but,  owing  to  the  unequal  lengths  of 
the  lateral  axes,  the  terminal  edges  are  of  two  kinds,  two  being  shorter 
and  more  obtuse  than  the  other  two. 

C. — FORMS  CONTAINED  UNDER  six  EQUAL  PLANES. — The  forms  here  in- 
cluded have  the  planes  parallelograms  ;  the  edges  are  twelve  in  number 
and  equal ;  the  solid  angles  eight. 

1.  Cube  (f.  14).  Faces  equal  squares,  and  plane  angles  therefore  90°. 
The  twelve  edges  similar  as  well  as  equal ;  the  eight  solid  angles  similar  and 
equal.  Interfacial  angles  90°.  The  three  axes  equal  and  intersecting  at 
right  angles. 

Lines  connecting  the  apices  of  the  solid  angles  are  the  octahedral  or  tri- 
gonal interaxes^  and  those  connecting  the  centres  of  opposite  edges  the 
dodecahedral  o?  rhombic  interaxes.  If  the  cubic  axis  (=edge  of  the  cube) 
=  1,  then  the  dodecahedral  interaxes  =  V%  —1.41421 ;  and  the  octahedral 
interaxes  =  4/8  —  1.73205.  And  if  the  dodecahedral  axis  =  1,  then  the 
octahedral  =  1.224745. 


14 


15 


IS 


If  a  cube  is  placed  with  the  apex  of  one  angle  vertically  over  that  diag-onally  opposite,  that 
is,  with  an  octahedral  interaxis  vertical,  the  parts  are  all  symmetrically  arranged  around 
this  vertical  axis.  In  this  position  (f.  15)  the  cube  has  three  planes  inclined  toward  one  apex, 
and  three  toward  the  other  ;  it  has  three  terminal  edges  meeting  at  each  apex  ;  and  six  late- 
ral edges  situated  symmetrically,  but  in  a  zigzag,  around  the  vertical  axis.  If  lines  are 
drawn  connecting  the  centres  of  the  opposite  lateral  edges,  and  these  are  taken  as  the  lateral 
axes,  the  lateral  axes,  three  in  number,  will  lie  in  a  plane  at  right  angles  to  the  vertical,  and 
will  intersect  at  the  centre  at  angles  of  60°.  The  cube  placed  in  this  position  would  then  have 


b  CRYSTALLOGRAPHY. 

one  vertical  and  three  equal  lateral  axes  ;    and  as  the  lateral  axes  correspond  to  the  dodeca- 
hedral  interaxes  of  a  cube,  the  ratio  of  a  lateral  axis  to  the  vertical  is  1 :  1. 224745. 


2.  Rhombohedron  (f.  16  to  18).  Faces  equal  rhombs.  The  twelve  edges 
of  two  kinds ;  six  obtuse,  and  six  acute.  Solid  angles  of  two  kinds  ;  two 
symmetrical,  consisting  each  of  three  equal  plane  angles ;  the  other  six  un- 
sjmmetrical,  the  plane  angles  enclosing  them  being  of  two  kinds. 

The  rhoinbohedron  resembles  a  cube  that  has  been  either  shortened,  or 
lengthened,  in  the  direction  of  one  of  the  octahedral  axes,  the  former  mak- 
ing an  obtuse  rhoinbohedron,  the  latter  an  acute;  and  it  is  in  position  when 
this  axis  is  vertical,  the  parts  being  situated  symmetrically  about  this  axis, 
as  in  the  second  position  of  the  cube  above  described.  In  an  obtuse  rhom- 
bohedron  (f.  16, 17),  the  terminal  solid  angles  are  bounded  by  three  obtuse 
plane  angles,  and  the  other  six,  which  are  the  lateral,  by  two  acute  and  one 
obtuse  ;  the  six  terminal  edges  (three  meeting  at  each  apex)  are  obtuse,  and 
the  six  lateral  edges  are  acute.  Conversely,  in  an  acute  rhoinbohedron  (f. 
18)  the  terminal  angles  are  made  up  of  acute  plane  angles,  and  the  lateral 
of  two  obtuse  and  one  acute ;  the  six  terminal  edges  are  acute,  and  the  six 
lateral  obtuse.  The  axes  are  a  vertical,  and  three  lateral ;  the  lateral  axes 
connect  the  centres  of  opposite  lateral  edges  and  intersect  at  angles  of  60°. 
The  cube  in  the  second  position  (f.  15)  corresponds  to  a  rhoinbohedron 
of  90°,  or  is  intermediate  between  the  obtuse  and  the  acute  series. 

D. — FORMS  CONTAINED  UNDER  TWELVE  EQUAL  PLANES.     1. 
Rhombic   Dodecahedron   (f.   19).     Faces   rhombs,  with  the 
plane  angles  109°  28'  16",  70°  31'  44".      Edges  twenty-four, 
all  similar ;    interfacial  angle  over   each  edge   120°.     Solid 
angles  of  two  kinds  :  (a)  six  acute  tetrahedral,  being  formed 
of  four  acute  plane   angles;  and   (b)  eight  obtuse  trihedral, 
being  formed  of  three  obtuse  plane  angles.     Angle  between 
planes  over  apex  of  tetrahedral  solid  angle,  90°  ;  angle  between 
edges  over  the  same  109°  28'  16".     The  axes  three,  equal, 
rectangular,  and  therefore  identical  with  those  of  the  regular  octahedron 
and   cube.     The  dodecahedral  interaxes  connect  the  centres  of  opposite 
faces  ;  and  the  octahedral  the  apices  of  the  trihedral  solid  angles.     Named 
from  ScoSe/ca,  twelve,  and  eBpa,  face. 

2.  Pyramidal  dodecahedron,  or  Qiiartzoid.  (Called 
also  Dihexagonal  Pyramid,  Isosceles  Dodecahedron.) 
Faces  isosceles  triangles,  and  arranged  in  two  pyramids 
placed  base  to  base  (f .  20).  Edges  of  two  kinds :  twelve 
equal  terminal,  and  six  equal  basal;  axes,  a  vertical  differ- 
ing in  length  in  different  species;  and  three  lateral,  equal, 
situated  in  a  plane  at  right  angles  to  the  vertical,  and  in- 
tersecting one  another  at  angles  of  60°,  as  in  the  rhoinbo- 
hedron. 

E. — PRISMS.— Prismatic  forms  consist  of  at  least  two  sets 
of  planes,  the  basal  planes  being  unlike  the  lateral.  The  bases  are  always 
equal ;  and  the  lateral  planes  parallelograms.  The  vertical  axis  is  unequal 
to  the  lateral,  (a)  Three-sided  prism.  A  right  (or  erect)  prism,  having 
its  bases  equal  equilateral  triangles,  (b)  Four-sided  prisms.  Four  sided 
prisms  are  either  right  (erect),  or  oblique,  the  former  having  the  vertical  axis 


CRYSTALLOGRAPHY. 


at  right  angles  to  the  base  or  to  the  plane  of  the  lateral  axes,  and  the  latter 
oblique. 

1.  Square  or  Tetragonal  Prism  (f.  21,  22V  Base  a  square  ;  lateral 
planes  equal.  Edges  of  two  kinds  :  (a)  eight  basal,  equal,  each  contained 
between  the  base  and  a  lateral  plane  ;  (b)  four  lateral,  contained  between  the 
equal  lateral  planes.  Interfacial  angles  all  90°,  plane  angles  90°.  Solid 
angles  eight,  of  one  kind.  Axes  :  a  vertical,  differing  in  length  in  different 
species,  and  longer  or  shorter  than  the  lateral ;  two  lateral,  equal,  at  right 
angles  to  one  another  and  to  the  vertical,  and  connecting  either  the  centres 
of  opposite  lateral  planes  (f.  21)  or  edges  (f.  22).  The  cube  is  a  square 
prism  with  the  vertical  axis  equal  to  the  lateral. 

22  23  24 


2.  Right  Rhombic  Prism  (f.  23).     Base  a  rhomb  ;  lateral  planes  equal 
parallelograms.    Edges  of  three  kinds  :  (a)  eight  basal,  equal,  and  rectan- 
gular as  in  the  preceding  form  ;  (b)  two  lateral,  obtuse ;  and  (c)  two  lateral, 
acute.     Solid  angles  of  two  kinds  ;  (a)  obtuse  at   the  extremities  of  the  ob- 
tuse edge,  and  (?)  acute  at  .the  extremities  of  the  acute  edge.     Axes  rect- 
angular,   unequal  ;    a    vertical  ;  a   longer  lateral,  the  macrodiagonal   axis 
(named  from    /aa/cpo?,  large),  and  a  shorter  lateral,  the  br  achy  diagonal  axis 
(named  from  #/>a£V9,  short). 

3.  Right  Rectangular  Prism  (f.  24).     Base  a  rectangle,   and  in  conse- 
quence of  its  unequal  sides,  two  opposite  lateral  planes  of  the  prism  are 
broader  than  the  other  two.     Edges  all  rectangular,  but  of  three  kinds  ; 
(a)  four  longer  basal  ;  (b)  four  shorter  basal  ;  (c)  four   lateral.     Axes  con- 
necting the  centres   of  opposite  faces,  rectangular,  unequal ;  a  vertical,  a 
macrodiagonal,  and  a  brachydiagcnal,  being  like  those  of  the  right  rhom- 
bic prism.     In  the  rectangular  prism,  either  of  the  faces  may  be  made  the 
basal,  and  either  axis,  consequently,  the  vertical. 

^4.  Oblique  Prisms.  Figs.  25  and  26  represent  prisms  oblique  in  the 
direction  of  one  axis.  As  seen  in  them,  the  vertical  axis  c  is  oblique  to  the 
lateral  axis  'd,  called  the  clinodiagonal  axis  ;  but  £,  the  orthodiagonal  axis, 
is  at  right  angles  to  both  c  and  d.  Similarly,  the  axial  sections  cb,  ba  are 
mutually  oblique  in  their  inclinations,  while  ca,  cb  and  ca,  ba  are  at  right 
angles.  The  clinodiagonal  section  ca  is  called  the  section  or  plane  of  sym- 
metry. 

The  form  in  f.  25  is  sometimes  called  an  oblique  rhombic  prism.  The 
edges  are  of  two  kinds  as  to  length,  but  of  four  kinds  as  to  iuterfacial  angles 
over  them  :  (a)  four  basal  obtuse ;  (b)  four  basal  acute  ;  (c)  two  lateral  ob- 
tuse :  (d)  two  lateral  acute.  The  prism  is  in  position  when  placed  with  the 
clinodiagonal  section  vertical. 

Figs.  27  and  28  show  the  doubly  oblique,  or  oblique  rhomboidal  prism, 
in  which  all  the  axes,  and  hence  all  the  axial  sections,  are  oblique  to  each 


8 


CRYSTALLOGRAPHY. 


other.     All  these  cases  will  receive  further  attention  in  the  description  of 
actual  crystalline  forms. 


28 


29 


The  prisms  (in  f .  21,  24,  26,  28)  in  which  the  planes  are  parallel  to  the 
three  diametral  sections,  are  sometimes  called  diametral  prisms.  This 
term  also  evidently  includes  the  cube.  The  planes  which  form  these 
diametral  prisms  are  often  called  pinacoids.  The  terminal  plane  is  the 
basal  pinacoid,  or  simply  base ;  also,  in  f.  24  the  plane  (lettered^)  parallel 
to  the  macrodiagonal  section  is  called  the  macropinacoid,  and  the  plane  (i-i) 
parallel  to  the  brachydiagonal  the  brachypinacoid.  In  f.  26  the  plane  (i-i) 
parallel  the  to  orthodiagonal  section  is  called  the  orthopinacoid,  and  the 
plane  (i-l)  parallel  to  the  clinodiagonal  section  the  chnopinacoid.  The 
word  pinacoid  is  from  the  Greek  7riva%,  a  board. 

(c).  SIX-SIDED  PRISM. —  The  Hexagonal  prism. 
Base  an  equilateral  hexagon.  Edges  of  two 
kinds:  (a)  twelve  basal, equal  and  similar,  (b)  six 
lateral,  equal  and  similar ;  jnterfacial  angle 
over  the  former  90°,  over  the  latter  120°.  Solid 
angles,  twelve,  similar.  Axes :  a  vertical,  of 
different  length  in  different  species ;  three  late- 
ral equal,  intersecting  at  angles  of  60°,  as  in  the 
rhombohedron,  and  the  dihexagonal  pyramid  or 

quartzoid,  connecting  the  centres  either  of  the  lateral  edges  (f.  29),  or  lateral 
faces  (f.  30). 

3.  SYSTEMS  OF  CRYSTALLIZATION. 

The  systems  of  crystallization  are  based  on  the  mathematical  relations  of 
the  forms  ;  the  axes  are  lines  assumed  in  order  to  exhibit  these  relations, 
they  mark  the  degree  of  symmetry  which  belongs  to  each  group  of  forms, 
and  which  is  in  fact  the  fundamental  distinction  between  them.  The  num- 
ber of  axes,  as  has  been  stated,  is  either  three  or  four — the  number  being 
four  when  there  are  three  lateral  axes,  as  occurs  only  in  hexagonal  forms. 

Among  the  forms  with  three  axes,  all  possible  conditions  of  the  axes  exist 
both  as  to  relative  lengths  arid  inclinations  ;  that  is,  there  are  (as  has  been 
exemplified  in  the  forms  which  have  been  described),  (A)  among  ortho- 
metric  kinds,  or  those  with  rectangular  axial  intersections ;  (a)  the  three 
axes  equal ;  (b)  two  equal,  and  the  other  longer  or  shorter  than  the  two  ;  (c) 
the  three  unequal ;  and  (B)  among  clinometric  kinds,  one  or  more  of  the 
intersections  may  be  oblique  (in  all  of  these  the  three  axes  are  unequal). 
The  systems  are  then  as  follows : 

A.  Axes  three  ;  orthometric. 

1.  ISOMETRIC  SYSTEM. — Axes  equal.  Examples,  cube,  regular  octahe- 
dron, rhombic  dodecahedron. 


CRYSTALLOGRAPHY.  9 

2.  TETRAGONAL  SYSTEM. — Lateral  axes  equal ;  the  vertical  a  varying  axis. 
Ex.,  square  prism,  square  octahedron. 

3.  ORTHORIIOMBIC   SYSTEM. — Axes  unequal.     Ex.,  right  rhombic  prism, 
rectangular  prism,  rhombic  octahedron. 

B.  Axes  three  ;  clinometric. 

1.  MONOCLINIC  SYSTEM. — Axes  unequal ;  one  of   the  axial  intersections 
oblique,  the  other  two  rectangular.     Ex.,  the  oblique  prisms  (f.  25,  26). 

2.  TRICLINIC  SYSTEM. — Axes  unequal ;  three  of  the  axial  intersections  ob- 
lique.    Ex.,  oblique  rhomboidal  prism  (f.  27,  28). 

C.  Axes  four. — P!EXAGONAL  SYSTEM. — Three  lateral  axes  equal,  intersect- 
ing  at  angles  of  60°.     The  vertical  axis  of  variable   length.     Example, 
hexagonal  prisms  (f.  29,  30). 

The  so-called  Diclinic  system  (two  oblique  axes)  is  not  known  to  occur,  for  the  single  sub- 
stance, an  artificial  salt,  supposed  to  crystallize  in  this  system  has  been  shown  by  von  Zepha- 
rovich  to  be  triclinic.  Moreover,  von  Lang,  Quenstedt,  and  others  have  shown  mathemati- 
cally that  there  can  be  only  six  distinct  systems. 

The  six  systems  may  also  be  arranged  in  the  following  groups : 

1.  Isometrie  (from  tcro?,  equal,  and  yuer/ooz^,  measure),  the  axes  being  all 
equal ;  including :  I.  ISOMETRIC  SYSTEM. 

2.  Isodiametric,  the  lateral  axes  or  diameters  being  equal ;  including : 
II.  TETRAGONAL  SYSTEM  ;  III.  HEXAGONAL  SYSTEM. 

3.  Anisometric  (from  awcro?,  unequal,  etc.),  the  axes  being  unequal ;  in- 
cluding :  IY.  ORTHORHOMBIC  SYSTEM  ;  Y.  MONOCLINIC  SYSTEM  ;    YI.  TRI- 
CLINIC SYSTEM. 

A  further  study  of  these  different  systems  will  show  that  in  group  1 
the  crystals  are  formed  or  developed  alike  in  all  three  axial  directions ;  in 
group  2  the  development  is  alike  in  the  several  lateral  directions,  but  un- 
like vertically ;  and  in  group  3  the  crystals  are  formed  unlike  in  all  three 
directions.  These  distinctions  are  of  the  highest  importance  in  relation  to 
the  physical  characters  of  minerals,  especially  their  optical  properties,  and 
are  often  referred  to  beyond. 

The  numbers  (in  Roman  numerals)  here  connected  with  the  names  of  the  system  are  often 
used  in  place  of  the  names  in  the  course  of  this  Treatise. 

The  systems  of  crystallization  have  been  variously  named  by  different  authors,  as  follows  : 

1.  ISOMETRIC.  Teasular  of  Mohs  and  Haidinger  ;  Isometric  of  Hausmann  ;  Tesseral  of  Nau- 
maiin ;  Regular  of  Weiss  and  Rose  ;  Cubic  of  Dufrenoy,  Miller,  Des  Cloizeaux ;  Monometric  of 
the  earlier  editions  of  Dana's  System  of  Mineralogy. 

2.  TETRAGONAL.     Pyramidal  of  Mohs;  Viergliedriege,  or  Zwei-und-einaxige,  of  Weiss; 
Tetragonal  of  Naumann  ;  Monodimetric  of  Hausmann  ;  Quadratic  of  von  Kobell ;  Dimetric  of 
early  editions  of  Dana's  System. 

3.  HEXAGONAL.     Rhombohedral  of  Mohs  ;    Sechsgliedrige,  or  Drd-und-einaoAge  of  Weiss; 
Hexagonal  of  Naumann  ;  Monotrimetric  of  Hausmann. 

4.  ORTHORHOMBIC.     Prismatic,    or  Ortlwtype,   of   Mohs;     Ein-und-einaxige    of  Weiss; 
Rhombic  and  Anisometric  of  Naumann;  Trimetric  and  OrtJiorJwmbic  of  Hausmann;    Trimtt- 
ric  of  earlier  editions  of  Dana's  System. 

5.  MONOCLTNIC.     Hemiprwmatic  and  Hemiortlwtype  of  Mohs ;    Zwei-und-einglicderige  of 
Weiss;  Monodinohcdral  of  Naumann  ;    ClincrlicmUc,  of  v.  Kobell,  Hausmann,  Des  Cloizeaux ; 
Augit.ic  of  Haidiuger ;   Oblique  of  Miller;   Monosyrnmetric  of  G-robh. 

G.  TRICLINIC.  Tetarto-prismatic  of  Mohs  ;  Ein-und-eingliederigc  of  Weiss ;  Tridinohedral 
of  Naumami ;  Clinorhomboidal  of  v.  Kobell ;  Anorthic  of  Haidinger  and  Miller  ;  A/wrthic,  or 
Doubly  Oblique,  of  Des  Cloizeaux  ;  Asymmetric,  of  Groth. 


10 


CRYSTALLOGRAPHY. 


4:.    LAWS    WITH    REFERENCE    TO    THE    PLANES    OF    CRYSTALS. 

The  laws  with  reference  to  the  positions  of  the  planes  of  crystals  are  two: 
first,  the  law  of  simple  mathematical  ratio;  secondly,  the  law  of  symmetry. 

1.  THE  LAW  OF  SIMPLE  MATHEMATICAL  KATIO. 

The  crystallographic  axes  afford  the  means,  after  the  methods  of  analyti- 
cal geometry,  of  expressing  with  precision  the  relative  positions  of  the 
planes  of  crystals,  and  so  exhibiting  the  mathematical  ratios  pertaining  to 
crystallization.  These  axes,  as  has  been  stated,  are  supposed  to  pass  through 
the  centre  of  the  crystal,  and  every  plane  must  intersect  one,  two,  or  three 
of  them.  The  position  of  a  plane  is  obviously  determined  by  the  position 

of  the  points  in  which  it  meets  these  axes. 
Thus  the  plane  AB  C,  f.  31,  meets  the 
three  axes  at  the  points  A,  B,  and  C,  and 
its  position  is  determined  by  the  dis- 
tances O  A,  O  B,  O  C,  intercepted  be- 
tween these  points  and  the  centre  O. 
Similarly  the  plane  A  B  D  meets  the 
axes  in  the  points  A,  B,  and  D,  and  its 
position  is  determined  by  the  distances 
O  A,  O  B,  O  D  ;  and  in  the  same  manner 
with  any  other  plane.  On  the  crystals 
of  a  given  species  the  occurring  planes 
have  exact  numerical  relations  to  each 
other,  and  it  is  to  show  these  relations 
that  certain  lengths  of  the  axes  are 
assumed  as  units.  Thus,  in  the  case 
already  given  if  O  C,  O  B,  O  A,  or  more 
briefly  o,  5,  a,  are  the  lengths  of  the 
axes  *  (strictly  speaking  semi-axes)  for  a 
given  species,  then  the  position  of  the 
first  plane  is  expressed  by  Ic  :  15  :  la ;  that  of  the  second  by  2c  :  Ib  :  la 
(if  OD=2OC),  and  still  another  plane  might  be  2c  :  26  :  la,  and  so  on. 
Consequently  the  general  position  of  any  plane  may  be  expressed  by 
me  :  nb  :  rafi  or  more  simply  mo  :  nb  :  a,  as  every  plane  is  for  simplicity 
supposed  to  meet  one  of  the  axes  at  the  unit  distance.  In  the  first  case 
mentioned  above,  m  —  1  and  n  —  1  ;  but  in  general  m  and  n  may  vary  in 
value  from  zero  to  infinity.  The  law  of  simple  mathematical  ratio,  how- 
ever, requires  that  m  and  n,  which  express  the  ratios  in  the  lengths  of  the 
axes,  should  be  invariably  rational  numbers,  and  in  general  they  are  either 
whole  numbers  or  simple  fractions. 

This  principle  may  be  stated  as  follows  : 

The  position  of  the  planes  in  a  given  crystal  is  related  in  some  simple 
ratio  to  t/ie  relative  lengths  of  the  axes. 

*  The  vertical  axis  is  throughout  called  c,  see  p.  53. 

f  It  is  more  usual,  and  analytically  more  correct,  to  write  this  expression  ra  :  nb  :  me ; 
but  as  the  usual  symbols  take  the  form  m-n,  the  order  of  the  terms  used  here  and  elsewhere 
is  more  convenient. 


CRYSTALLOGRAPHY. 


11 


This  subject  will  become  clear  in  the  subsequent  study  of  the  different 
crystalline  forms  ;  in  passing,  however,  reference  may  be  made 
to  f.  32  (zircon)  as  a  single  example.  The  planes  lettered  1 
and  3  have  respectively  the  positions,  le  :  15  :  10,  and  3c  :  Ib  :  la, 
and  in  the  second  case  the  vertical  axis  has  exactly  three  times 
the  length  of  that  of  the  former  ;  any  such  multiples  as  2.93  or 
3.07  are  crystallographically  impossible.  It  is  this  principle 
which  makes  crystallography  an  exact  mathematical  science. 
Some  apparent  exceptions,  such  as  occasionally  occur,  do  not  at 
all  set  aside  this  rule. 

The  expression  me  :  nb  :  a  is  called  the  symbol  of  a  plane,  as  it  expresses 
its  exact  mathematical  position,  and  the  values  of  m  and  n  are  called  its 
parameters.  If  a  plane  intersects  two  of  the  axes,  but  not  the  third,  it 
is  parallel  to  it,  and  mathematically  it  is  said  to  cut  it  at  infinity  (oo  )  ; 
hence  the  general  expression  for  a  plane  parallel  to  the  vertical  axis  c  (as  in 
f  .  33)  will  be  oo  c  :  nb  :  a,  or  GO  G  :  b  :  na,  according  as  a  or  b  is  taken  as 
the  unit  ;  for  a  plane  parallel  to  the  lateral  axis  b  (as  in  f.  34),  it  will  be 
me  :  oo  b  :  a  ;  if  parallel  to  the  lateral  axis  a  (as  in  f  .  35),  me  :  b  :  oo  a. 

If  a  plane  is  parallel  to  two  axes,  b  and#,  that  is,  intercepts  these  axes  at 


33 


34 


an  infinite  distance,  its  position  is  expressed  by  G  :  oo  b  :  oo  a,  as  is  illus- 
trated by  f.  36  ;  again,  its  position  is  expressed  by  oo  G  :  b  :  oo  0,  if  parallel 
to  G  and  a ;  and  by  oo  c  :  oo  b  :  a,  if  parallel  to  c,  b.  These  may  also  be 
written  Oc  :  b  :  a,  etc. 

The  following  important  principle 
should  be  kept  in  mind.  The  relative 
not  the  absolute  position  of  any  plane 
has  to  be  regarded,  and  hence  all 
planes  parallel  to  each  other  are 
crystallographically  identical.  A 
plane  on  the  angle  of  the  cube  is  the 
same,  if  the  mutual  inclinations  re- 
main unchanged,  whether  large  or 
small,  for,  though  the  actual  distances 
cut  off  on  the  axes  may  differ  in  each 
case,  the  ratios  of  these  axes  are  iden- 
tical. Again,  in  f.  37,  the  three  planes, 
4c  :  45  :  20,  and  2c  :  25  :  a,  and  c  : 
b  :  \a  are  identical,  for  the  ratios 
of  the  three  axes  are  the  same 
throughout,  the  planes  being  of  course 
parallel.  Similarly  the  symbol  Ic  :  £5  :  %a  may  be  written  3<? :  b  :  a, 


12  CRYSTALLOGRAPHY. 

and  c  :  oo  b  :  oo  a  is  the  same  as  Oe  :  b  :  a.  It  will  be  seen  that  this  prin- 
ciple makes  it  right  to  regard  every  plane  as  meeting  one  of  the  axes  at 
the  unit  distance  from  the  centre,  which,  as  before  stated,  reduces  the 
general  expression  of  any  plane  me  :  nb  :  ra  to  the  simpler  form  me :  rib  :  a, 
or  me  :  b  :  na. 

The  principle,  which  has  just  been  stated,  also  makes  it  evident  that  when 
the  axes  are  all  equal,  they  are  not  necessarily  considered  in  naming  the 
position  of  any  plane  ;  when  the  lateral  axes  alone  are  equal,  a  certain 
length  of  the  vertical  axis  must  be  assumed  for  each  species  ;  and  when  all 
the  axes  are  unequal,  certain  lengths  for  two  of  the  axes,  expressed  in 
terms  of  the  third  axis,  must  in  every  case  be  adopted. 

Hence  the  fundamental  form  of  any  species  may  be  regarded  as  that 
octahedron  whose  axes  correspond  in  relative  lengths  with  the  axes  c,  b,  a 
adopted  for  the  species.  The  faces  of  this  octahedron  intersect  the  axes  at 
distances  from  the  centre  equal  to  ne,  nb.,  na  (or  c  :  b  :  a)  respectively,  and, 
since  the  ratio  of  the  coefficients  which  expresses  the  position  of  these 
planes  is  1:1:1,  this  form  is  also  called  the  unit  octahedron.  But  the 
form  is  not  necessarily  fundamental ;  for  it  is  frequently  more  or  less  arbi- 
trarily assumed,  and  the  structure  or  genesis  of  the  crystals  of  a  species  may 
point  to  other  forms,  having  very  different  axial  relations,  as  will  appear 
from  facts  stated  beyond. 

MODELS. — For  clear  illustration  of  the  axes  and  axial  ratios  of  planes  it  is  well  to  have 
models  of  the  axes  made  of  rods  of  wood  mortised  and  glued  together  at  the  crossing  at  centre. 
The  rods  may  be  half  an  inch  in  diameter  and  10  or  12  inches  long;  for  the  Isometric  system, 
three  equal  rods,  say  12  inches  long  ;  for  the  Tetragonal  system,  two  of  12  inches  for  the 
lateral  axes  and  one  of  8  or  14  inches  for  the  vertical ;  for  the  Orthorhombic,  one  of  16  inches 
for  axis  £,  one  of  10  inches  for  axis  c,  and  one  of  14  inches  for  axis  a.  (Either  axis  may  be 
made  the  vertical  by  way  of  change.) 

For  the  Clinometric  systems,  make  a  second  model  like  that  for  the  Orthorhombic  system, 
but  with  the  rods  but  loosely  mortised  and  tied  together,  so  as  to  admit  of  a  little  movement 
at  centre.  Then,  the  model  when  in  its  more  natural  position  will  be  that  of  the  orthorhom- 
bic  system,  the  intersections  being  all  rectangular.  But  by  pushing  the  front  rod  a  down  in 
the  plane  of  ca,  making  it  thus  oblique  to  c,  while  at  right  angles  to  b,  the  model  will  repre- 
sent the  monoclinic  axes  ;  if  all  the  intersections  of  the  rods  are  oblique,  the  model  will 
represent  the  axes  of  the  Triclinic  system. 

Now  by  taking  a  large  piece  of  thick  pasteboard,  and  placing  it  in  different  positions  with 
reference  to  the  three  axes,  the  relations  to  the  various  planes  may  be  readily  illustrated. 

Models  of  the  various  forms  of  crystals  are  also  of  the  highest  importance  ;  and  the  best 
for  general  illustration  are  those  made  of  plate  glass,  some  of  them  having  the  positions  of 
the  axes  within  indicated  by  threads,  and  others  consisting  of  one  form  inside  of  another  to 
show  their  mutual  relations.  Such  glass  models  (first  made  by  Professor  Dana,  in  1835, 
and  recommended  in  the  first  edition  of  his  Mineralogy)  are  now  manufactured  of  great  per- 
fection at  Siegen,  in  Germany. 

Pasteboard  models,  likewise  useful  aids  to  the  study  of  crystallography,  are  easily  made 
from  the  outlines  of  the  faces  of  the  various  forms,  which  have  been  prepared  by  various 
authors. 

Models  cut  in  hard  wood  representing  the  actual  forms  of  the  various  mineral  species  are 
very  valuable,  when  accurately  made.  They  not  only  show  the  relations  of  different  planes, 
but  may  also  be  advantageously  used  to  give  the  student  practice  in  the  mathematical  cal- 
culations of  the  axes  and  parameters, ,  the  angles  being  measured  by  him  as  on  an  actual 
crystal.  Such  models  have  the  advantage  of  being  of  convenient  size,  and  symmetrically 
formed,  which  are  conditions  not  often  realized  in  the  crystals  furnished  by  nature. 

2.  LAW  OF  SYMMETRY. 
The  symmetry  of  crystals  is  based  upon  the  law  that  either  : 


CRYSTALLOGRAPHY.  13 

I.  All  parts  of  a  crystal  similar  in  position  with  reference  to  the  axes 
are  similar  in  planes  'or  modification,  or 

IL  Each  half  of  the  similar  parts  of  a  crystal,  alternate  or  symmetri- 
cal in  position  or  relation  to  the  other  half,  may  be  alone  similar  in  its 
planes  or  modifications. 

The  forms  resulting  according  to  the  first  method  are  termed  holohe- 
dral  forms,  from  6\o?,  all,  eBpa,  face  ;  and  those  according  to  the  second, 
hemihedral,  from  rj/jua-vs,  half. 

According  to  the  law  of  full  or  holohedral  symmetry,  each  sectant  in  one 
of  the  rectangular  systems  (a)  should  have  the  same  planes  both  as  to  num- 
ber and  kind  ;  and  (b)  whatever  the  kinds,  in  each  sectant  there  should  be 
as  many  of  each  kind  as  are  geometrically  possible.  But  in  hemihedrism, 
either  (a)  planes  of  a  kind  occur  only  in  half  of  the  sectants  ;  or  else  (b) 
half  the  full  number  occur  in  all  the  sectants. 

In  the  isometric  system,  for  example,  if  one  solid  angle  of  a  cube  has 
upon  it  a  plane  equally  inclined  to  the  diametral  sections,  so  will  each  of  the 
other  angles  (or  sectants)  (f.  39-42). 

If  one  of  the  twelve  edges  of  the  cube  has  a  plane  equally  inclined  to  the 
enclosing  cubic  faces  (or  diametral  planes)  the  others  will  have  the  same 
(f.  43-46). 

Again,  one  of  the  solid  angles  of  a  cube  being  replaced  by  six  planes,  as 
in  f  .  70,  this  law  requires  that  the  same  six  planes  should  appear  on  all  the 
other  solid  angles. 

But  under  the  law  of  hemihedrism  these  planes  may  occur  on  half  the 
solid  angles  of  the  cube,  and  not  on  the  other  half,  as  in  f.  87,  or  half  the 
full  number  of  planes  may  occur  on  all  the  angles,  as  in  f.  101.  This  subject 
is  further  elucidated  in  the  discussion  of  the  hemihedral  forms  belonging 
to  each  system  of  crystallization. 

HEMIHEDKISM  is  of  various  kinds  : 

1.  Holomorphic,  in  which    the  occuring  planes  pertain  equally  to  both 
the  upper  and  lower  (or  opposite)  ranges  of  sectants,  as  in  all  ordinary  hemi- 
hedral forms. 

2.  Hemim.orphic,  in  which  the  planes  pertain  to  either  the  upper  or  the 
lower  range,  and  not  to  both,  and  hence  the  planes  are  only  half  enough  of 
the  kind  to  enclose  a   space,  whence  the  term  hemimorphic,  from  ij/jii<rv$9 
half,  and 


The  holomorphic  forms  may  be  either  : 

A.  Hemiholohedral,  HALF  the  sectants  having  the  FULL  number  of  planes, 
or 

B.  Holohemihedral,  ALL  the  sectants  having  HALF  the  whole  number  of 
planes. 

Again,  as  to  the  relative  positions  of  the  sectants  containing  the  planes, 
the  forms  may  be  : 

a.  Vertically-direct,  in  which  the  sectants  of  the  upper  and  of  the  lower 
ranges  are  alternate,  but  the  upper  not  alternate  with  reference  to  the  lower, 


CRYSTALLOGRAPHY. 


and,  accordingly,  eacli  plane  above  is  in  the  same  vertical  zone  with  a  like 
plane  below  ;  as  in  forms  described  on  pp.  34,  35. 

b.  Vertically-alternate,   in   which  the  sectants  of  the  upper  and  lower 
ranges  are  alternate,  and  also  the  upper  are  alternate  with  reference  to  the 
lower,  and,  accordingly,  each  plane  above  is  not  in  the  same  vertical  zone 
with  alike  plane  below;  as  in  the  tetrahedron  (f.  9),  rhombohedron  (f.  16), 
and  gyroidal  forms  (f.  182). 

c.  Vertically-oblique,  in  which  the  sectants  of  the  upper  and  lower  ranges 
are  adjacent,  but  the  upper  are  situated  diagonally  with  reference  to  the 
lower,  being   on  the   opposite  side   of  a   transverse  diametral  or  diagonal 
plane  ;  as   in  hemihedrons  of  monoclinic   habit  under  the  orthorhombic 
system  (p.  45). 

Tetartohedrism. — Mathematically  the  rhombohedron  is  a  hemihedron  un- 
der the  hexagonal  system,  consequently  the  forms  that  are  hemihedral  to  the 
rhombohedron  are  tetartohedrons,  or  quarter-forms.  See  p.  39. 

Tetartohedral  forms,  or  those  with  one-fourth  of  the  normal  number  of 
planes,  have  also  been  observed  in  the  Isometric  system.  The  term  mero- 
hedrism,  from  yu-epo?,  part,  and  e§pa,  face,  has  been  used  in  place  of  hemi- 
hedrism,  to  include  both  this  and  tetartohedrism. 


L_ISOMETKIC  SYSTEM. 
A.  Holohedral  Forms. 

In  the  ISOMETRIC  SYSTEM  the  axes  are  equal,  so  that  either  one  may  be  the 
vertical  axis,  and  each  may  be  called  a.  It  has  already  been  shown  that  the 
general  expression  for  any  plane  meeting  the  axes  c,  l>,  a  is  me  :  nl> :  a ;  and 
in  this  system  it  will  be  ma  :  na  :  a,  or,  since  the  axes  are  equal,  simply 
m  :  n  :  1.  Now  it  has  been  shown  also  that  according  as  a  plane  intersects 
the  several  axes  at  different  points,  or  is  parallel  to  one  or  more  of  them, 
this  fact  is  indicated  by  the  values  given  for  m  and  n  in  each  case  (p.  11). 
Hence  expressions  for  all  the  forms  geometrically  possible  in  this  system 
will  be  obtained  if  to  m,  and  n,  in  the  general  expression  ma  :  na  :  a,  succes- 
sive values  are  given.  These  values  may  be  in  this  system,  0, 1,  a  number 
greater  than  l,"or  co  .  In  this  way  are  derived  : — 

1  [_m-n\  when  m  and  n  have  both  different  values  greater 

than  unity. 

1  \m-m~]  when  m  >  1.  n  —  m. 

1  \m\  when  m  >  1,  n  =1. 

1  [1]  when  m  and  n  =  1. 

1  [i-ri\  when  m  —  QO  ,  n  >  1. 

1  \i\  when  m  —  GO  ,  n  =  1. 


1.     m 


2.  m 

3.  m 

4.  1 

5.  oo 

6.  oo 

7.  oo 


n 


1       [IT]      when  m  and  n  = 


In  lettering  the  planes  of  the  several  forms  only  the  essential  part  of  the  symbol  is  used:  the 
cube  is  H  (hexahedron) ;  the  octahedron  l(=l  :  1  :  1)  ;  the  dodecahedron  *  (oo  :  1  :  1),  (  i 
stands  for  infinity) ;  m  is  used  for  the  planes  m  :  1  :  ]  ;  m-m  f  or  m  :  m  :  1 ;  i-n  f  or  oo  :  n  :  1 ; 


ISOMETKIC    SYSTEM. 


15 


m-n  for  m  :  n  :  1.  These  symbols  are  the  same  as  those  of  Naumann,  except  that  he  wrote 
oo  instead  of  i  for  infinity,  and  introduced  also  the  letter  0  (octahedron)  as  the  sign  of  the 
system  ;  oo  0  oo  of  his  system^//;  0=1  ;  oo  0=1  ;  m  0=m  ;  m  0  m=m-m,  GO  0  n=i-n, 
and  m  0  H=m-n. 

Each  of  these  expressions,  appearing  at  first  sight  possibly  a  little 
obscure,  may  be  translated  into  simple  language. 

Cube. — The  cube  with  the  symbol  oo  :  oo  :  1,  is  composed  of  planes  each 
one  of  which  is  parallel  to  two  of  the  axes,  and  meets  the  third  at  its  unit 
point  (see  f.  36).  It  is  evident  that  there  are  six  such  planes,  one  at  each 
extremity  of  the  three  axes,  and  the  figure  or  crystal  which  is  enclosed  by 
these  six  planes  has  already  been  described  (p.  5)  as  the  cube  (f.  38). 

Octahedron. — The  symbol  1:1:1  comprises  all  those  planes  which  meet 
the  three  axes  at  the  same  distance,  that  is,  cut  off  the  unit  length  of  each. 
It  is  evident  that  there  must  be  eight  such  planes,  one  in  each  octant,  and 
they  together  form  the  regular  octahedron  (f.  42),  which  has  already  been 
described,  p.  4. 

Dodecahedron. — The  symbol  oo  :  1 :  1  includes  those  planes  which  inter- 
cept two  of  the  axes  at  the  same  unit  distance,  and  are  parallel  to  the 
third.  There  can  be  twelve  planes  answering  to  these  conditions,  and  they 
form  together  the  dodecahedron  (f.  45,  see  also  p.  6). 

These  three  forms,  the  cube,  octahedron,  and  dodecahedron,  are  those 
most  commonly  occurring  in  this  system,  and  it  is  important  that  their  rela- 
tion should  be  thoroughly  understood.  The  transitions  between  these  forms, 
as  they  inodify  one  another,  are  exhibited  in  the  following  figures  : 


53!) 


40 


41 


42' 


Figs.  38  and  42  represent  the  cube  and  octahedron,  and  39,  40,  41,  the 
intermediate  forms.  Slicing  off  from  the  eight  angles  of  a  cube  piece  after 
piece,  sucl^that  the  planes  made  are  equally  inclined  to  H,  or  the  cubic  faces, 
the  cube  is  finally  converted  into  the  regular  octahedron  ;  and  the  last 
disappearing  point  of  each  face  of  the  cube  is  the  apex  of  each  solid  angle 
of  the  octahedron.  The  axes  of  the  former,  therefore,  of  necessity  connect 
the  apices  of  the  solid,  angles  of  the  latter. 

The  form  in  f.  40  is  called  a  cubo-octahedron.     ^A  1=125°  15'  52". 

If  the  twelve  edges  of  the  cube  are  truncated  (for  all  will  be  truncated  if 
one  is)  it  affords  the  form  in  f .  43  ;  then  that  of  f .  44  ;  then  the  dodecahe- 


16 


CRYSTALLOGRAPHY. 


drcm,  f.  45  ;  the  axes  of  the  cube  becoming,  in  the  transition,  the  axes  con- 
necting the  tetrahedral  solid  angles  of  the  dodecahedron  ;  II A  i  =  135°.  If 
the  twelve  edges  of  the  octahedron  (f,  42)  are  truncated,  the  form  in  f.  47 
results  ;  and  by  continuing  the  replacement,  finally  the  dodecahedron  again 
is  formed  (f.  45).  1  A  i  =  144°  44'  8".  The  last  point  of  the  face  of  the 
octahedron,  as  it  disappears,  is  the  apex  of  the  trihedral  solid  angle  of  the 
dodecahedron. 

These  forms  are  thus  mutually  derivable.  The  process  may  be  reversed, 
the  cube  beinoj  derivable  from  the  dodecahedron  by  the  truncation  of  the 
tetrahedral  solid  angles  of  the  latter  (compare  in  succession  f.  45,  44,  43, 
38)  ;  and  the  octahedron  by  the  truncation  of  the  trihedral  solid  angles 
(compare  f.  45,  47,  42).  These  remarks  are  important  as  showing  the  rela- 
tions between  these  forms,  though  it  is  of  course  not  intended  to  be  under- 
stood that  they  are  in  any  sense  derived  from  each  other  in  this  manner  in 
nature. 

The  three  axes  (or  cubic  axes)  connect  the  centres  of  opposite  faces  in  the 
cube  ;  the  apices  of  opposite  solid  angles  in  the  octahedron ;  the  apices 
of  opposite  tetrahedral  solid  angles  in  the  dodecahedron. 

The  eight  trigonal  or  octahedral  interaxes  connect  the  centres  of  opposite 
•faces  in  the  octahedron  /  the  apices  of  opposite  solid  angles  in  the  cube  ; 
the  apices  of  opposite  trihedral  solid  angles  in  the  dodecahedron. 

The  twelve  rhombic  or  dodecahedral  interaxes  connect  the  centres  of  op- 
posite faces  in  the  dodecahedron  •  the  centres  of  opposite  edges  both  in  the 
cube  and  the  octahedron. 

In  a  vertical  section,  containing  each  of  these  kinds  of  axes,  the  octahe- 
dral interaxis  intersects  one  of  the  three  cubic  axes  at  the  angles  54°  44'  8" 
and  125°  15'    52",   and  one  of  the 
dodecahedral  interaxes,  at  the   an-  48 

2-les  35°  15'  52"  and  144°  44'  8". 


There  remain  four  other  holohe- 
dral  forms  belonging  to  the  system 
as  contained  in  the  list  on  page  14. 

Trisoctahedro-ns.  —  The  symbol 
m  :  1  :  1  is  of  that  solid  each  of 
whose  planes  meets  two  of  the  axes 
at  the  unit  distance,  and  the  third 
axis  at  some  distance  which  is  a 
multiple  of  this  unit  length.  It  will 
be  evident,  as  in  f.  48,  that  there 
are  three  such  planes  in  each  of  the 
eight  sectants,  and  hence  the  total 
number  of  planes  by  which  the  solid 
is  bounded  is  twenty-four.  The 
resulting  solid  is  called  a  trigonal 
trisoctahedron,  and  one,  having 
m=f,  is  shown  in  f.  49. 


It  will  be  found  a  very  valuable  practice  for  the  student  to  construct  the  figures  of  the 
successive  crystalline  forms  in  this  way,  laying  off  the  proper  lengths  of  the  several  axes  and 


ISOMETRIC    SYSTEM. 


17 


notinflfthe  points  where  the  different  planes  intersect.     Further  remarks  on  the  drawing  of 
crystals  will  be  found  in  the  Appendix. 

The  symbol  m  :  m  :  1  belongs  to  all  the  planes  which 
meet  one  axis  at  the  unit  distance,  and  the  others  at  equal 
distances  which  are  multiples  of  the  former.  As  seen  in  the 
preceding  case,  there  will  be  three  such  planes  in  each  of 
the  eight  sectaiits,  and  the  total  number  consequently  will 
be  twenty-four.  The  solid  is  seen  in  f.  50,  and  is  called  a 
tetragonal  trisoctaJiedron,  or  a  trapezohedron. 

Both  these  forms  are  called  trisoctahedrons,  from  r/ot?,  three  times,  and 
octahedron,  because  in  each  a  three-sided  pyramid  occupies 
the  position  of  the  planes  of  the  regular  octahedron.  They 
are  closely  related  to  each  other ;  starting  with  the  form 
m  :  1  :  1,  if  m  is  diminished  till  it  equals  unity,  then  the 
symbol  becomes  1:1:1,  that  is,  it  has  passed  into  the  octa- 
hedron. If  m  becomes  less  than  unity,  the  symbol  maybe, 
for  example,  ^  :  1  :  1,  which  is  identical,  as  has  been  ex- 
plained (p.  11)  with  1:2:2  (2-2),  and  this  is  the  symbol  of 
the  second  trisoctahedron.  This  explains  why,  in  the  first  list  comprising 
all  the  possible  forms,  m  was  in  no  case  made  less  than  unity. 

Trigonal-trisofitahedron. — In  this  form  the  solid  angles  are  of  two 
kinds  :  the  trigonal  or  octahedral,  and  the  octagonal  or  cubic.  The  edges  are 
thirty-six  in  number,  twenty-four  of  one  kind,  forming  the  octahedral  or 
trihedral  solid  angles,  and  twelve  edges  meeting  at  the  extremities  of  the 
cubic  axes.  Each  of  the  twenty-four  planes  is  an  isosceles  triangle. 


52 


In  combination  with  the  cube,  the  form  2  appears  as  a  replacement  of 
each  of  the  solid  angles  by  three  planes  equally  inclined  on  the  edges  /  this 
is  seen  in  f.  52.  With  the  octahedron,  it  appears  as  a  bevelment  of  its 
twelve  edges,  as  shown  in  f.  53.  It  also  replaces  the  eight  trigonal  solid 
angles  of  a  dodecahedron  by  three  planes  inclining  on  the  faces.  The  more 
commonly  occurring  examples  of  this  form  are  2  (=2  :  1  :  1),  also  f  (=f 
:  1  :  1),  and  3  (3  :  1  :  1). 

The  Tetragonal-trisoctahedron  or  trapezohedron,  has  three  kinds  of  solid 
angles  :  six  cubic,  whose  truncations  are  cubic  faces  (f.  56) ;  eight  octahe- 
dral, whose  truncations  are  octahedral  faces  (f.  56) ;  twelve  dodecahedral, 
truncated  by  the  dodecahedral  planes  (f.  60).  It  has  forty-eight  edges ; 
twenty-four  of  one  kind,  those  of  the  trihedral  or  octahedral  solid  angles, 
and  the  remaining  twenty-four,  also  of  one  kind,  meeting  in  the  cubic  solid 
angles.  Each  of  the  twenty-four  faces  is  a  quadrilateral. 

In  combination  with  the  cube  it  is  seen  in  f.  55,  56,  appearing  as  a  re- 
placement of  each  of  the  solid  angles  by  three  planes  equally  inclined  on 
2 


18 


CRYSTALLOGRAPHY. 


the  faces  of  the  cube.  Figs.  56,  57,  58,  59,  60,  62,  also  show  it  in  com- 
'bination  with  the  octahedron  and  dodecahedron.  The  most  commonly 
occurring  of  this  series  is  2-2  (  =  2  :  2  :  l),f.  54  ;  as  seen  in  f.  59,  it  truncates 
the  twenty-four  edges  of  the  dodecahedron.  On  the  other  hand  the  form 

56  57  58 


54 


55 


60 


01 


f-f  would  replace  the  trihedral  solid  angles  by  planes  inclined  on  the  edges, 
while  3-3  replaces  (f.  62),  the  tetrahedral  solid  angles  of  the  dodecahedron, 
by  planes  also  inclined  on  the  edges. 

Tetrahexahedron. — The  symbol  oo  :  n  :  1  (i-n)  belongs  to  all  the  planes 
which  are  parallel  to  one  axis,  meet  a  second  at  the  unit  distance,  and  the 
third  at  some  multiple  of  that.  There  are  twenty-four  planes  which  satisfy 
these  conditions,  and  they  form  the  tetrahexahedron  /  f.  64, 65,  represent  two 
varieties  of  tetrahexahedrons.  It  will  be  seen  that  the  planes  are  so 
arranged  that  a  square  pyramid  corresponds  to  each  of  the  six  faces  of  the 
cube  ;  and  hence  the  name  from  rerpa/a?,  four  times,  ef,  six,  and  eSpa, 
face,  it  being  a  4x6-faced  solid.  The  tetrahexahedron  has  six  tetrahe- 
dral solid  angles  and  eight  hexahedral  or  octahedral  solid  angles.  There  are 
twenty-four  edges  of  one  kind  forming  the  former  solid  angles,  and  twelve 
edges  occupying  the  position  of  the  cubic  edges.  Each  of  the  twenty-four 
faces  is  an  isosceles  triangle.  In  combination  with  the  cube  it  produces  a 
bevelment  of  its  twelve  edges,  as  represented  in  f .  64. 


64 


occurring  kinds  are 


The  tetrahexahedron,  in  f.  67>,  lettered  £-2,  has  the  symbol  oo :  2  :  1 ;  and 
that  of  f.  66,  lettered  *-3,  oo :  3  :  1.     Some  of  the  other 
those  with  the  ratios,  2  :  3,  3  :  4,  4  :  5,  etc.,  etc. 

The  relation  of  the  tetrahexahedron  to  the  octahedron  is  shown  in  f.  67. 
By  comparing  this  figure  with  f.  42,  it  is  seen  that  the  planes  i-%  replace 


ISOMETRIC    SYSTEM. 


19 


the  solid  angles  of  the  octahedron  by  planes  inclined  on  its  edges.  Its  rela- 
tion to  the  dodecahedron  is  presented  in  f.  68,  w^hich  is  a  dodecahedron 
(planes  i  being  the  dodecahedral  planes,  see  f.  45)  with  the  tetrahedral  solid 
angles  replaced  by  four  planes  inclined  each  on  an  i. 

The  tetrahexahedron  is  called  a  fluoroid,  by  Haidinger,  the  form  being 
common  in  fluorite.  It  is  the  Tetrakishexahedron  (or  Pyramidenwiirfet) 
of  Naumann. 

In  accordance  with  considerations  already  presented  it  is  evident  that  n, 
in  the  symbol  i-n,  may  always  be  written  as  a  whole  number,  for  the  symbol 
co  :  i  :  1  is  identical  with  QO  ;  1  :  2.  Moreover  it  is  seen  that  when  n  is  oo  , 
the  form  passes  into  the  cube  (oo  :  GO  :  1),  and  as  n  diminishes  and  becomes 
unity,  it  passes  into  the  dodecahedron  (oo :  1  :  1). 

Hexoctahedron. — The  general  form  m  :  n  includes  the  largest  number 
of  similar  planes  geometrically  possible  in  this  system.  This  symbol 
requires  six  planes  in  each  octant,  as  will  be  seen  by  a  method  of  con- 
struction similar  to  that  in  f.  48,  and  consequently  the  whole  solid  has 
forty-eight  planes.  It  is  hence  called  a  hexakisoctahedron  (efa/u?,  six 
times,  OKTW,  eight,  and  e'fya,  face,  i.e.,  a  6  x  8-faced  solid)  or  hexoctahedron. 
The  form  is  shown  in  f .  69,  where  it  will  be  seen  that  there  are  three  differ- 
ent kinds  of  edges,  and  three  kinds  of  solid  angles;  each  of  the  forty- 
eight  planes  is_a  scalene  triangle. 

When  modifying  the  cube  it  appears  as  six  planes  replacing  each  of  the 
solid  angles,  f.  70.  It  replaces  the  eight  angles  of  the  octahedron,  and  the 

69  *  70 


form  3-f  bevels  the  twenty-four  edges  of  the  dodecahedron  (f.  71).  Other 
hexoctahedrons,  differing  in  their  angles,  may  replace  the  six  acute  solid  an- 
gles of  the  dodecahedron  by  eight  planes,  or  the  eight  obtuse  by  six  planes. 
The  hexoctahedron  of  f.  69,  70,  71  is  that  whose  planes  have  the  axial 
ratio  3  :  f  :  1.  Others  have  the  ratio  4  :  2  : 1,  2  :  f  :  1  (=6  :  4  :  3),  5  :  f  :  1 
(=15  :  5  :  3),  7  :  f  :  1  (=21  :  7  :  3),  etc. 

72  73 


Amalgam. 


Magnetite. 


20 


CRYSTALLOGRAPHY. 


The  preceding  figures  show  dodecahedrons  variously  modified.  In 
f.  72,  7,  or  i,  are  faces  of  the  dodecahedron ;  Hoi.  the  cube  ;  1  of  the  octa- 
hedron; i-3  of  a  tetrahexahedron  (f.  66) ;  2-2  of  the  trapezohedron  of  f.  54, 
59 ;  3-f  of  the  hexoctahedron  of  f.  69,  70.  In  f.  73,  i,  O,  and  1  are  as  in 
f.  72  ;  3-3  is  the  trapezohedron  of  f.  61,  62 ;  and  5-f  (either  side  of  3-3)  a 
hexoctahedron. 

The  hexoctahedron  is  called  the  adamantoid  by  Haidinger,  in  allusion 
to  its  being  a  common  form  of  crystals  of  diamond.  It  is  the  hexakisocta 
liedron  of  JSauinanh. 

B.  Hemihedral  Forms. 

Of  the  kinds  of  hemihedral  forms  mentioned  on  page  13,  the  hemiho 
lohedral,  in  which  only  half  of  the  sectants  are  represented  in  the  form, 
produces  what  are  called  inclined  hemihedrons  /  and  the  holokemihedral,  in 
which  all  the  sectants  are  represented  by  half  the  full  number  of  planes, 
parallel  hemihedrons.  In  the  former  the  sectants  to  which  the  occurring 
planes  belong  are  diagonally  opposite  to  those  without  the  same  planes ;  and 
hence  no  plane  has  another  opposite  and  parallel  to  it ;  on  the  contrary, 
opposite  planes  are  oblique  to  one  another,  and  hence  the  name  of  inclined 
hemihedrons  applied  to  them.  They  are  also  called  tetrahedral  forms,  the 
tetrahedron  being  the  simplest  form  of  the  number,  and  its  habit  character- 
istic of  them  all;  while  the  latter  are  called  pyritohedral,  because  observed 
in  the  species  pyrite.  The  complete  symbols  of  the  inclined  hemihedrons 
are  written  in  the  general  form  \(in  :  n  :  1),  of  the  parallel  hemihedrons 
in  the  form  -§-  [r/i  :  n  :  1]  ;  also  written  K,(m  :  n  :  1)  and  7r(m  :  n  :  1)  re- 
spectively. 

a.  Inclined  or  Tetrahedral  Hemihedrons.  1.  Tetrahedron,  or  Hemi- 
octahedron. — -|(1  :  1  :  1). 

As  has  been  shown,  the  form  1(1  :  1  :  1)  embraces  eight  planes,  and  when 
holohedrally  developed  it  produces  the  octahedron ;  in  accordance,  how- 
ever, with  the  law  of  hemihedrism,  half  of  the  eight  possible  planes  may 


74 


76 


76A 


77 


78 


70 


80 


occur  in  alternate  octants;  thus  in  two  opposite  sectants  above,  and  the 
two  diagonally  opposite  below,  as  shown  by  the  shaded  planes  in  f.  74.     If 


ISOMETEIC    SYSTEM.  21 

these  four  shaded  planes  are  suppressed,  while  the  other  four  of  the  octa- 
hedron are  extended,  the  resulting  form  is  the  regular  tetrahedron,  f.  76. 
The  relation  of  the  octahedron  and  tetrahedron  maybe  better  understood 
from  f.  75.  if,  as  just  remarked,  the  planes  shaded  in  f.  74  are  suppressed, 
while  the  others  are  extended,  it  will  be  seen  in  f.  75  that  the  two  latter 
pairs  intersect  in  edges  parallel  respectively  to  the  basal  edges  of  the 
octahedron,  and  the  complete  tetrahedron  is  the  result.  The  axes,  it  is  im- 
portant to  observe,  connect  the  middle  points  of  the  opposite  edges. 

Further  than  this,  since  either  set  of  four  planes  may  go  to  form  the  solid, 
two  tetrahedrons  are  evidently  possible,  and  they  may  be  distinguished 
by  calling  the  first,  f.  76,  positive,  and  the  second  negative,  f.  76A. 
These  terms  are  of  course  only  relative.  The  plus  and  the  minus  tetrahe- 
drons may  occur  in  combination,  as  in  f.  79  ;  and  though  there  are  here  pre- 
sent the  eight  planes  which  in  holohedral  forms  make  the  octahedron,  and 
though  they  should  happen  to  be  equally  developed  so  as  to  give  the  same 
shape,  the  crystal  would  still  be  pronounced  tetrahedral,  since  the  planes 
1  and  — 1  are  physically  different.  An  example  of  this  occurs  in  crystals 
of  boracite,  where  the  planes  of  one  tetrahedron  are  polished  while  those  of 
the  other  are  without  lustre. 

The  plane  angles  of  the  tetrahedron  are  60D,  and  the  interfacial  angles 
70°  31'  4A". 

The  combinations  of  the  cube  and  tetrahedron  are  shown  in  f .  77  and  78, 
and  the  dodecahedron  and  tetrahedron  in  f .  80.  As  the  octahedron  results 
geometrically  from  slicing  off  successively  the  solid  angles  of  the  cube,  by 
planes  of  equal  inclination  on  the  cubic  faces,  so  also  the  tetrahedron  may 
be  made  mechanically  by  slicing  off  similarly  half  these  solid  angles. 

81  82  83  84 


Hemi-trisoctahedrons,  \(m  :  m  :  l)and  %(m  :  1  :  1).  In  the  same  manner 
as  with  the  tetrahedron,  the  form  m-m,  when  hemihedral,  may  have  half  its 
twenty-four  planes  present,  viz.,  those  in  the  two  opposite  sectants  above 
and  the  alternate  sectants  below.  When  these  twelve  planes  are  extended, 
the  others  being  suppressed,  they  form  the  solid  represented  in  f.  81  ;  the 
symbol  properly  being  £(  m->m),  or  here  i(2-2).  The  faces,  as  will  be  ob 
served,  are  trigonal,  and  the  solid  is  sometimes  called  a  cuproid.  There  is 
the  same  distinction  to  be  made  here  between  the  plus  and  the  minus  forms 
as  with  the  tetrahedrons.  Figs.  82,  83,  84  show  combinations  of  -\-\(m-m) 
with  the  plus  tetrahedron,  the  dodecahedron,  and  the  tetrahexahedron. 

Similarly  the  form  m,  when  hemihedral,  according  to  the  same  principle 
results  in  the  solid,  f.  85.  It  is  called  the  deltohedron  by  Haidinger  ;  it  has 
trapezoidal  faces.  In  f.  86,  +i(f)  ^s  shown  in  combination  with  +-J-(2-2). 
Here  also  the  distinction  between  the  plus  and  minus  forms  is  to  be  made  in 
the  same  manner  as  that  already  explained. 


22 


CRYSTALLOGRAPHY. 


Inclined  or  tetrahedral  ffemi-hexoctaJiedron  \(m  :  n  :  I).  The  form  m-n 
when  developed  according  to  the  law  of  inclined  hemihedrism,  that  is, 
when  of  its  forty-eight  faces,  half  are  present,  viz.,  all  in  half  the  whole 


85 


86 


87 


number  of  sectants,  ^produces  the  solid  seen  in  f.  87.  There  is  here  also  a 
plus  solid,  and  a  minus  solid,  corresponding  to  the  +  and  —  tetrahedron. 
In  f.  88  it  is  in  combination  with  the  plus  tetrahedron. 

If  the  same  method  of  inclined  hemihedrism  be  applied  to  the  remain- 
ing solids  of  this  system,  the  cube,  dodecahedron,  and  tetrahexahedron,  that 
is,  if  in  each  case  the  parts  in  two  opposite  sectants  above,  and  the  two  diag- 
onally opposite  sectants  below,  be  conceived  to  be  extended,  the  other  half 
being  suppressed,  it  will  be  seen  that  the  solid  reproduces  itself  ;  the  hemi- 
hedral  form  of  the  cube  is  the  cube,  and  so  of  the  others. 

The  following  figures  represent  some  other  combinations  of  these  forms. 


89 


89A 


90 


Sphalerite. 


Sphalerite. 


Tetrahedrite. 


In  f .  89,  the  cuproid  3-3  is  combined  with  the  faces  I  of  a  dodecahedron. 
The  form  3-3  resembles  closely  that  of  f.  81,  but  in  its  combination  with 
the  dodecahedron  it  does  not  truncate  an  edge  of  the  dodecahedron,  like  2-2 
in  f .  83.  Fig.  89A  contains  the  same  planes  combined  with  the  plus  tetra- 
hedron, hexagonal  planes  1,  the  minus  tetrahedron,  triangular  planes  1,  and 
the  faces  of  the  cube  II.  The  .presence  of  the  plane  /^facilitates  the  com- 
parison of  the  form  with  f.  55,  56,  57,  p.  18,  the  plane  3-3  having  the  same 
position  essentially  with  2-2.  Fig.  90  has  as  its  most  prominent  planes  those 
of  f .  81  ,  but  the  position  given  it  is  relatively  to  f .  81  that  of  the  minus 
hemihedron  ;  and  there  are  also  the  small  planes  2-2  about  the  angles, 
wThich  are  those  of  the  minus  hemihedron.  H,  are  planes  of  the  cube  ; 
1,  those  of  the  tetrahedron;  ^',  those  of  the  dodecahedron  ;  i-3  those  of  a 
tetrahexahedron  (H,  i,  i-3  all  holohedral)  ;  and  f  the  planes  of  a  deltohe- 
dron  similar  to  f .  85,  and  occurring  with  2-2  in  f.  86. 


ISOMETKIC    SYSTEM. 


23 


b.  Parallel  or  pyritohedral  hemihedrons.  —  According  to  the  second  law 
of  hemihedrism,  half  the  whole  number  of  planes  of  any  form  may  be  pre- 
sent in  all  the  sectants.  In  the  resulting  solids  each  plane  has  another  par- 
allel to  it.  This  method  of  hemihedrism  obviously  produces  distinct  f  owns 
only  in  those  cases  where  there  is  an  even  number  of  planes  in  each  octant. 

Pentagonal  Dodecahedron,  or  Hemi-tetrahexahedron,  -J(oo  :  n  :  I).  If 
of  the  twenty-four  planes  of  the  form  i-n(oc  :  n  :  1),  only  half  are  present  ; 
viz.,  one  of  each  pair  in  the  manner  indicated  by  shading  in  f.  91,  these 
being  extended  while  the  others  are  suppressed,  the  solids  in  f.  92  and  f.  93 
result.  The  parallelism  of  each  pair  of  opposite  planes  will  be  seen  in  these 
figures.  These  two  possible  forms,  seen  in  the  figures,  are  distinguished  by 
calling  one  plus  (arbitrarily),  -f-J  [V-2],  and  the  other  minus,—  ^  [^-2].  These 
solids  are  very  common  in  the  species  pyrite,  and  are  hence  called  QijriJ.olia- 
drons  •  they  are  also  called  pentagonal  dodecahedrons,  in  allusion  to  their 
pentagonal  faces.  The  regular  dodecahedron  of  geometry  belongs  to  this 
class,  but  is  an  impossible  form  in  nature,  since  for  it  n  must  have  an  irra- 

" 


tional  value,  viz., 


1  i 

'' 


,  see  p.  10. 


In  combination  with  the  cube  the  form  -f  i[^'-2]  is  seen  in  f.  94  and  f.  95, 
and  in  f.  96,  97,  with  the  octahedron,  and  in  f.  98,  with  the  cube  and  octa- 
hedron. 


91 


93 


94 


98 


Parallel   hemi-hexoctahedron,   %\_m  :  n  :  1].     When   of  the  forty-eight 
planes  of  the   form  m-n,  only  half  are  present,  viz.,  the  three    alternate 


99 


101 


E lanes  in  each  octant  as  indicated  by   the  shading  in  f.  99,  the  solid   in 
100  results.     This  solid  is  called  a  diploid  by  Haidinger.     It  is  also  called 


24 


CRY  STALLOGEAPH  Y. 


a  dyakis-dodecahedron.     In  f .  101  it  is  shown  in  combination  with  the  cube, 
and  inf.  102  with  the  octahedron. 

Figs.  103,  104,  105,  of  the  species  pyrite,  represent  various  combina- 
tions of  parallel  hemihedrons  with  the  cubic  and  other  faces.  In  f.  103 
there  are  planes  of  twohemi-tetrahexahedrons  (pentagonal  dodecahedrons) 
2-2,  fc-J-  •  and  of  two  diploids  4-2,  3-J,  along  with  planes  of  the  octahedron, 
1,  and  of  the  trapezohedron  2-2.  In  f.  104  the  dominant  form  is  the  dode- 
cahedron, /;  it  has  the  faces  of  the  cube,  H\  of  the  octahedron,  1  ;  of  the 


103 


104 


Pyrite. 


Pyrite. 


Pyrite. 


trapezohedron,  2-2 ;  and  of.  the  parallel  hemihedrons,  2-2  and  4-2.  Fig. 
105  represents  a  map  of  one  angle  of  a  cube,  showing  at  centre  the  octahe- 
dral face  1,  and  around  it  the  faces  of  the  cube  .//,  of  the  trapezohedron 
2-2,  the  trigonal  trisoctahedron  2,  and  the  parallel  hemihedrons,  i-2,  2-±, 
3-f .  The  axial  ratio  for  2-f  is  2  :  |  :  1  (or  6:4:2),  and  for  3-f ,  3  :  |  :  1 
(or  6:3:2). 

Prominent  distinctive  characters. — The  student,  in  order  to  facilitate  his 
study  of  Isometric  forms  in  nature,  should  be  thoroughly  familiar  with  the 
following  points,  from  the  study  of  models  or  natural  crystals ;  (1)  The 
isometric  character  of  the  symmetry,  the  planes  being  alike  in  grouping  in 
the  direction  of  the  three  axes.  (2)  The  forms  of  the  faces  and  solid  an- 
gles of  the  octahedron,  the  dodecahedron,  the  trapezohedron  2-2,  the  pen- 
tagonal dodecahedron  i-2.  (3)  The  fact  that  the  following  are  common  an- 
gles in  the  system— 135°  (=H/\*);  109°  28'  (angle  of  octahedron),  70°  32' 
(angle  in  octahedron  and  tetrahedron) ;  120°  (angle  of  dodecahedron);  125° 
16'  (=HAl);  144° 44'  (=HA2-2  =  lAa);  153°  26;(=HA*-2);  161°  34'  (=H 
A*-3).  A  list  of  the  angles  belonging  to  the  various  forms  of  this  system  is 
given  on  p.  67.  (4)  Cleavage  may  be  cubic,  octahedral,  or  dodecahedral  • 
and  sometimes  two  of  these  kinds,  and  occasionally  the  three,  occur  in  the 
same  species,  but  always  with  great  difference  of  facility  between  them. 
Galenite  is  an  example  of  easy  cubic  cleavage ;  flnorite  of  easy  octahedral ; 
sphalerite  (blende)  of  easy  dodecahedral. 

Planes  of  symmetry. — The  seven  kinds  of  solids  described  on  pp.  15  to  19, 
include  all  the  holohedral  forms  possible  in  this  system,  as  is  evident  from 
their  geometrical  development.  In  them  exists  the  highest  degree  of  sym- 
metry possible  in  any  geometrical  solids. 

In  the  cube,  as  has  already  been  stated,  all  planes,  solid  angles,  and  edges 
are  equal  and  similar.  The  three  diametral  planes,  passing  each  through 
two  of  the  axes,  are  the  chief  planes  of  symmetr3T,  every  part  of  the  crystal 


TETRAGONAL    SYSTEM. 


on  one  side  of  the  plane  having  its  equal  and  symmetrical  part  on  the  oppo- 
site side.  Further  than  this,  each  of  the  six  planes  passing  through  the 
diagonal  edges  of  the  cube,  and  consequently  parallel  to  the  dodecahedral 
planes,  are  also  planes  of  symmetry.  There  are  hence  in  this  system  nine 
planes  of  symmetry. 


IL—  TETKAGORAL    SYSTEM. 

In  the  TETRAGONAL  SYSTEM,  there  are  three  rectangular  axes  ;  but  while 
the  two  lateral  axes  are  equal,  the  remaining  vertical  axis  is  either  longer  or 
shorter  than  they  are  ;  there  are  consequently  to  be  considered  the  lateral 
axes  (a)  and  the  vertical  axis  (c). 

The  general  geometrical  expression  for  the  planes  of  crystals  becomes  for 
this  system  me  :  na  :  #,  and,  if  this  be  developed  in  the  same  way  as  the  cor- 
responding expression  in  the  Isometric  system,  all  the  forms*  geometrically 
possible  are  derived. 

1.       me  :  na  :  a  [in-n]  when  m  >1,  n  >1. 

o      j  c  :  a  :  a  [1]  when  m—\^  n=l. 

^'    \  me  :  a  :  a  [m]  when  m^l,  74=  1. 

c  :  oo  a  :  a  [1--&]  when  w=l,  n—^>  . 

mo  :  oo  a  :  a  \m-i\  when  m^l,  n=ao  . 

.4.       oo  c  :  na  :  a  \i-n~]  when  m-=<x>  ,  n  >1. 

5.  oo  G  :  a  :  a  [7]  when  m=co  ,  n=\. 

6.  oo  c  :  oo  a  :  a  [i-i\  when  m=oo  ,  n=vz  . 
(c  :  oo  a  :  <*>  a)  [<?]  when  m=Q,  n=1. 
or  Oc  :  a  :  a. 


j 
| 


In  lettering  the  planes  the  abridged  symbols  are  used;  here,  as  before,  f=oo  ,  and  the  unit 
term  is  omitted  as  unnecessary,  me  :  <x>a  :  a—m-i,  etc.  These  are  the  same  as  the  symbols 
of  Naumann,  except  that  he  wrote  oo  ,  and  added  P  as  the  sign  of  the  systems  which  are  not 
isometric  ;  QP=0  ;  oo/^oo  =i-i  |  ooP—  /;  oo  Pn—i-n  ;  mPoo  =m-i  ;  mP=m  ;  P—  1  ;  and 
uiPn=m-n. 

A.  Holohedral  Forms. 

Basal  plane.  —  There  are  two  similar  planes  corresponding  to  the  sym- 
bol c  :  oo  a  :  oo  a  (or  Qc  :  a  :  a),  parallel  to  both  the  lateral  axes  ;  each  is 
called  the  basal  plane.  They  do  not  inclose  a  space,  and  consequently  they 
can  occur  only  in  combination  with  other  planes. 

Prisms.  —  The  planes  having  the  symbol  oo  G  :  oo  a  :  a  are  parallel  to  the 
vertical  and  one  of  the  lateral  axes.  There  are  four  such  planes,  one  at 
each  extremity  of  the  two  lateral  axes,  and,  in  combination  with  the  plane 
O,  they  form  the  square  prism,  which  has  been  called  the  diametral  prism, 
seen  in  f.  106. 

For  the  symbol  oo  a  :  a  :  a,  the  planes  are  parallel  to  the  vertical  axis, 

*  The  word  form  has  been  freely  used  in  the  preceding  pages  ;  from  this  point  on,  how- 
ever, it  needs  to  be  more  exactly  denned.  In  a  crystallographic  sense  it  includes  all  the 
planes  geometrically  possible,  never  less  than  two,  which  have  the  same  general  symbol. 


26 


CRYSTALLOGRAPHY. 


and  meet  the  others  at  equal  distances.  There  are,  as  in  the  preceding 
case,  four  such  planes.  They  form,  in  combination  with  the  plane  O, 
that  square  prism  which  is  seen  in  f.  107,  and  may  be  called  the  unit 
prism.  Both  the  prisms  i-i  and  /  are  alike  in  their  degree  of  symmetry. 
Each  has  four  similar  vertical  edges,  and  eight  similar  basal  edges  unlike 
the  vertical.  There  are  also  in  each  case  eight  similar  solid  angles. 


107 


108 


109 


i  a 


n 


12 


The  form -i-n  (oo  c  :  na:  a)  is  another  prism,  but  in  this  each  plane  meets 
one  of  the  lateral  axes  at  the  unit  distance,  and  the  other  at  some  multiple 
of  its  unit  distance.  As  is  evident  in  the  accompanying  horizontal  section 
(f.  113),  this  general  symbol  requires  eight  similar  planes,  two  in  each 
quadrant,  and  the  complete  form  is  shown  in  f.  109.  The  sixteen  basal 
edges  are  all  similar ;  the  vertical  edges  are  of  two  kinds,  four  axial  X,  and 
four  diagonal  Y  (f.  109).  The  regular  octagonal  pyramid  with  eight  similar 
vertical  edges,  each  angle  being  135°,  is  crystallographically  impossible. 


Ill 


112 


The  planes  I  truncate  the  edges  of  the  diametral  prism  i-i,  as  in  f.  108. 
Similarly  the  planes  i-i  truncate  the  vertical  edges  of  /.  The  prism  i-n  be- 
vels the  edges  of  i-i,  as  in  f.  110,  where  i-n—i-2. 

The  relation  of  the  two  square  prisms,  i-i  and  /,  may  be  further  illus- 
trated by  the  figs.  Ill  and  112.  In  f.  112  the  sections  of  the  two  prisms 
are  shown  with  the  dotted  lines  for  the  axes,  and  in  f.  Ill  there  are  the 
two  forms  complete,  the  one  (/)  within  the  other  (i-i).  The  unit  prism  /is 
sometimes  called  the  prism  of  the  first  series,  and  the  prism  i-i  that  of  the 
second  series. 

Octahedrons  or  Pyramids. — The  forms  m-i  and  m  both  give  rise  to 
square  octahedrons,  corresponding  to  the  two  kinds  of  square  prisms.  In 
tn-i  the  planes  are  parallel  to  one  lateral  axis  and  meet  the  vertical  axis 
at  variable  distances,  multiples  (denoted  by  m)  of  the  unit  length.  The 
total  number  of  such  planes,  for  a  given  value  of  m,  is  obviously  eight,  and 


TETRAGONAL    SYSTEM. 


27 


the  form  is  shown  in  f.  114  and  115.  These  planes  replace  the  basal 
edges  of  the  form  shown  in  f.  106,  and  m  varies  in  value  from  0  to  oo . 
When  m=0  the  four  planes  above  and  below  coincide  with  the  two  basal 

116 


planes ;  as  m  increases,  there  arises  a  series,  or  zone,  of  planes,  with  mu- 
tually parallel  intersections  (f.  116)  ;  and  when  m— oo  ,  the  octahedral  planes 
m-i  coincide  with  the  planes  i-i.  The  value  of  m  in  a  particular  species 
depends  upon  the  unit  value  assumed  for  the  vertical  axis  c. 

The  same  form  replaces  the  vertical  angles  of  the  prism  /,  as  in  f.  117. 


The  octahedrons  of  the  m  series  meet  both  of  the  lateral  axes  at  equal 
distances  and  the  vertical  axis  at  variable  distances.  It  is  clear  that  the 
whole  number  of  planes  for  this  form,  when  the  value  of  mis  given,  is  also 
eight,  one  in  each  octant.  When  m  =  l  the  solid  in  f.  118  is  obtained, 
which  is  sometimes  called  the  unit  octahedron.  As  m  decreases,  the  octahe- 
drons become  more  and  more  obtuse,  till  m— 0,  when  the  eight  planes  coin- 
cide with  the  two  basal  planes.  As  m  increases  from  unity,  on  the  other 
hand,  the  octahedrons  or  pyramids  become  more  and  more  acute,  and  when 
m—^>  they  coincide  with  the  prism  /;  this  series  forms  another  zone  of 
planes.  These  octahedrons  replace  the  basal  edges  in  the  form  f.  107,  as 
seen  in  f.  119,  and  as  the  octahedron  is  more  and  more  developed  it  passes 
to  f .  120,  and  finally  to  f .  118. 


The  same  form  replaces  the  solid  angles  of  the  form  f.  106,  as  seen  in 
f.  121,  and  this  too  gradually  passes  into  f.  122  and  f. 


28 


CRYSTALLOGRAPHY. 


125 


The  relation  of  the  octahedrons  1  and  \-i  (m  and  m-i)  is  the  same  as  that 
of  the  prisms  /  and  i-i  (compare  f.  112).  Similarly,  too,  they  are  often 
called  octahedrons  (or  pyramids)  of  the  first  (m)  and  second  (m-i)  series. 

As  will  be  seen  in  f.  123,  \-i  truncates  the  pyramidal  edges  of  the  octahe- 
dron 1,  and,  conversely,  the  edges  of  the  octahedron  2-i  are  truncated  by 
the  octahedron  1  (f.  124). 

Octagonal  pyramids. — The  form  m-n  (me  : 
na  :  a)  in  this  system  has,  as  in  the  preceding  sys- 
tem, the  highest  number  of  similar  planes  which 
are  geometrically  possible  ;  in  this  case  the  num- 
ber is  obviously  sixteen,  two  in  each  of  the  eight 
sectants,  as  in  f.  125,  where  w=l,  n=2.  These 
sixteen  similar  planes  together  form  the  octagonal 
pyramid  (strictly  double  pyramid)  or  zirconoid, 
f.  126.  It  has  two  kinds  of  terminal  edges,  the 
axial  X  and  the  diagonal  Y ;  the  basal  edges  are 
all  similar.  It  is  seen  (m-n=l-%)  in  f.  127  in 
combination  with  the  diametral  prism,  and  in  f.  128  with  1,  where  it  bevels 
the  vertical  edges. 

126 


Other  tetragonal  forms  are  illustrated  in 
figures  2  to  8,  of  zircon  crystals,  on  p.  2  ; 
f.  8  is  the  most  complex,  and  besides  3-3 
shows  also  the  related  zirconoids  4-4  and  5-5. 

Several  series  of  forms  occur  in  f.  129,  of 
vesuvianite.  In  the  unit  series  of  planes 
there  are  the  octahedrons  (or  pyramids)  1,^2, 
3,  and  the  prism  /;  in  the  diametral  series 
1-^,  i-i  ;  of  octagonal  prisms,  i-2,  i-3 ;  of  zir- 
conoids 2-2,  3-3,  5-5,  4-2-  f-3,  the  whole  num- 
ber of  planes  being  154. 


B.  Hemihedral  Forms. 

Among  hemihedral  forms  there  are  two  divisions,  as  in   the  isometric 
system  :  .  „   , 

1.  Hemiholohedral,  having  the  full  number  of  planes  in  half  the  sectants. 
(a)  Vertically-alternate,  or   sphenoidal  forms.— The  planes  occur  in  two 
sectants  situated  in  a  diagonal  line  at  one  extremity,  and  two  in  the  trans 
verse  diagonal  at  the  other. 


TETRAGONAL    SYSTEM. 


29 


With  octahedral  planes  ^(mc  :  a '.  a]  the  solid  is  a  tetrahedron  (f.  130, 
131)  called  a  sphenoid,  having  the  same  relation  to  the  square  prism  of 


130 


132 


134 


f.  106  that  the  regular  tetrahedron  lias  to  the  cube.  Fig.  130  is  t\\.Q  positive 
sphenoid  or  +  l,^and  131  the  negative,  or  —1.  The  form  \(mc  :  oo  a  :  a) 
is  similar.  Fig.  132  represents  the  sphenoid  in  combination  with  the  prism 
i-L 

If  the  planes  of  each  sectant  are  the  two  of  the  octagonal  pyramid 
%(mc  :  na  :  -a)  (f.  126),  the  form  is  a  diploid  (f.  133).  It  is  in  combination 
with  the  octahedron  l-i  in  f.  134. 

(b)  Vertically-direct,  or  the  planes  occuring    in  two   opposite  sectants 
above,  and  in  two  on  the  same  diagonal  below.     The  result  is  a  horizontal 
prism,  or  forms  resembling  those  of  the  orthorhombic  system.     Character- 
izes crystals  of  edin^tonite. 

(c)  Vertically-oblique.     Planes  occurring  in  two  adjacent  octants  above, 
and  in  two  diagonally  opposite  below,  producing  monoclinic  forms,  as  in  a 
hydrous  ammonium  sulphate. 

2.  Ilololiemihedral,  all  the  sectants  having  half  the  full  number  of  planes. 
As  the  largest  number  of  planes  of  a  kind  is  two,  half  the  full  number  is 
in  all  cases  one.  Hemihedrism  may  occur  in  the  forms  m-n  (f.  126,  127), 
or  zirconoids,  and  in  the  forms  i-n  (f.  109),  or  the  octagonal  prism. 

The  following  are  the  kinds  : 

(a)  Vertically-direct.  The  occurring  plane  of  the  sectants,  the  right 
one  in  the  upper  series,  and  that  in  the  same  vertical  zone  below,  as  indi- 
cated by  the  shading  in  f.  135  ;  or  else  the  left  one  above,  and  that  in  the 
same  vertical  zone  below,  f.  136. 


135 


(b)  Vertically-alternate.  The  occurring  plane  the  right  above,  and  that 
in  the  alternate  zone  below,  as  indicated  in  f.  137 ;  or  else  the  left  above, 
and  that  in  the  alternate  zone  below,  f.  138. 

As  the  right  of  the  two  planes  above  is  in  the  same  vertical  zone  with  the 
left  of  the  two  below  (supposing  the  lower  end  made  the  upper),  the  two 
kinds  of  the  first  division  will  be  the  rl  m-n  ;  and  the  Ir  m-n  (in  f.  136  on 
the  angles  of  the  prism  i-i]  ;  and  the  two  of  the  second  division  the  rr  m-n 
and  the  II  m-n  (in  f.  138,  on  the  angles  of  the  prism  i-i). 


30 


CRYSTALLOGRAPHY. 


The  completed  form  for  the  first  methods  has  parallel  faces,  and  is  like  the 
ordinary  square  octahedron  in  shape,  because  the  upper  and  lower  planes 
belong  to  the  same  vertical  zone.  But  in  the  second  it  is  gyroidal  •  the 
upper  pyramid  has  its  faces  in  the  same  vertical  line  with  an  edge  of  the 
lower,  as  represented  in  f.  139,  the  form  II  m-n. 

The  first  of  these  methods  occurs  in  octagonal  prisms,  producing  a  square 
prism,  either  r  i-n,  or  I  i-n. 

Fig.  140  represents  a  com-  140 

bination  of  the  octahedron  \-i 
with  the  unit-octahedron  1,  and 
two  hemihedral  forms,  one  of 
them  IT  1-2,  the  other  rl  3-3, 
The  plane  1  shows  the  posi- 
tion of  the  octant  ;  3-3  is  to 
the  right  of  1,  and  1-2  to  the 
left.  In  f.  141,  which  is  a  top 
view  of  a  crystal  of  wernerite, 
there  occurs  I  3-3  large,  along 
with  r  3-3  small,  indicating 
hemihedrism,  and,  judging 
from  that  of  the  allied  species 
sarcolite,  it  is  of  the  square  oc-  Scheelite. 

tahedral  kind,  rl  3  3  and  IT  3-3. 
Fig.  142  contains  the  hemihedral  prism  I  i-±,  com- 
bined  with  the  unit-octahedron    1,  and   the   basal 
plane  O. 


Wernerite. 


Wuifenite. 


Variable  elements  in  this  system.  —  In  the  tetragonal  system  two  ele- 
ments are  variable,  and  in  any  given  case  must  be  decided  before  the  rela- 
tions of  the  forms  can  be  definitely  expressed. 

(a)  The  position  of  the  lateral  axes.  —  These  axes  are  equal,  but  there  are 
two  possible  positions  for  them,  for  in  a  given  square  octahedron  they  may 
be  either  diagonal  or  diametral;  in  other  words,  given  an  octahedron,  as  in 
f.  115,  116,  the  prismatic  planes  may  be  made  diametral  (i-i),  and  the  octahe- 
dron so  belong  to  the  m-i  series,  or  the  prismatic  planes  may  be  made  diag- 
onal, that  is  /  (oo  G  :  a  :  a),  when  the  corresponding   octahedrons   belong 
to  the  m  series.     The  ratio  of  the  lateral  axes  for  the  two  cases  is  obviously 

1  :  1/2,  or  1  :  1.4142  +. 

(b)  The  length  of  the  vertical  axis.  —  Among  the  several  occurring  octa- 
hedrons, one  must  be  assumed  as  the  unit,  and  the  others  referred  to  it.     In 
f.  143,  of  zircon,  the  octahedron  1  is  made  the  unit,  and  by  measur- 

ing the  basal  angle  it  is  found  mathematically,  as  explained  later, 

that  the  length  of  the  vertical  axis  is  0.85  times  that  of  the  lateral 

axes.     The  octahedron  3  has  then  the  symbol  3c  :  a  :  a  as  referred 

to  this  unit.     If  the  latter  octahedron  had  been  taken  as  the  fun- 

damental form,  the  length  of  the  vertical  axis  would  have  been 

3  x  0.85  times  that  of  the  lateral  axes,  and  the  symbol  of  the  first 

plane  would  have  been  \c  :  a  :  a.     Which  form  is  to  be  taken  as 

the  unit  or  fundamental,  that  is,  what  length  of  the  vertical  axis  c  is  to  be 

adopted,  depends  upon  various  considerations.      In  general  that  form  is 


143 


HEXAGONAL   SYSTEM.  31 

assumed  as  fundamental  which  is  of  most  common  occurrence  or  to  which 
the  cleavage  is  parallel ;  or  which  best  shows  the  morphological  relations 
of  the  given  species  to  others  related  to  it  in  chemical  composition,  or  which 
gives  the  simplest  symbols  for  the  occurring  forms  of  a  species. 

Prominent  characteristics  of  ordinary  tetragonal  forms. — The  promi- 
nent distinguishing  characteristics  of  tetragonal  forms  are  :  (1)  A  symme- 
trical arrangement  of  the  planes  in  fours  or  eights.  (2)  The  frequent  oc- 
currence of  a  square  prism  diagonal  to  a  square  prism,  the  one  making  with 
the  other  an  angle  of  135°.  (3)  The  occurrence  of  bevelling  planes  on  the 
lateral  edges  of  the  square  prism.  (4)  A  resemblance  of  the  octahedrons 
to  the  regular  octahedron,  in  having  a  square  base,  but  a  dissimilarity  in 
that  the  angles  over  the  basal  edges  do  not  equal  those  over  the  terminal.  (5) 
Cleavage  may  be  either  basal,  square-prismatic,  or  octahedral  /  prismatic 
cleavage,  when  existing,  is  alike  in  two  directions,  parallel  to  the  lateral 
faces  of  one  of  the  square  prisms,  and  is  always  dissimilar  to  the  basal  cleav- 
age; the  basal,  or  the  lateral,  is  sometimes  indistinct  or  wanting;  the  pris- 
matic may  occur  parallel  to  the  lateral  planes  of  both  square  prisms,  but 
when  so,  that  of  one  will  be  always  unlike  in  facility  that  of  the  other. 

Planes  of  symmetry. — There  are  five  planes  of  symmetry  in  the  tetra- 
gonal system  :  one  principal  plane  of  symmetry  normal  to  the  vertical  axis, 
and  four  others,  intersecting  in  this  axis  ;  these  four  are  in  two  pairs,  the 
planes  of  each  pair  normal  (90°)  to  each  other,  and  diagonal  (45°)  to  those 
of  the  other. 


III.— HEXAGONAL  SYSTEM. 

The  HEXAGONAL  SYSTEM  includes  two  grand  divisions  :  1.  The  HEXA- 
GONAL proper,  in  which  (1)  symmetry  is  by  sixes,  and  multiples  of  six  ; 
.(2)  hemihedral  forms  are  of  the  kind  called  vertically-direct ;  and  (3) 
cleavage  and  all  physical  characters  have  direct  relations  to  the  holohedral 
hexagonal  form. 

2.  The  RHOMBOHEDKAL,  in  which  (1)  symmetry  is  by  threes  and  multi- 
ples of  three,  rhombohedral  forms  being  hemihedral  in  mathematical  rela- 
tion to  the  hexagonal  system,  and  of  the  kind  called  vertically-alternate ; 
(2)  cleavage,  and  many  other  physical  characters,  usually  partake  of  the 
hemihedrism. 

While  the  rhombohedron  is  mathematically  a  hemihedral  form  under 
the  hexagonal  system,  and  is  properly  so  treated  in  a  system  of  mathema- 
tical crystallography,  it  is  not  so  genetically,  or  in  its  fundamental  relations. 
Moreover,  it  has  its  own  hemihedral  forms,  which,  under  the  broad  hexago- 
nal system,  are  tetartohedral. 

The  holohedral  forms,  all  of  which  belong  to  the  Hexagonal  division, 
are  here  first  described  ;  and  then  the  hemihedral  forms,  which  include,  be- 
sides a  few  under  the  hexagonal  division,  the  whole  of  the  Rliombohedral 
division. 

A.  Holohedral  Forms  :  HEXAGONAL  DIVISION. 

The  general  expression  for  planes  of  this  system  is  me  :  na  :  a  :  pa,  where 
there  are  to  be  considered  the  vertical  axis,  c,  and  three  equal  lateral  axes,  a. 


dZ  CRYSTALLOGRAPHY. 

It  is  evident,  however,  that,  the  position  of  any  plane  is  determined  by  its 
intersections  with  two  of  the  lateral  axes,  as  its  direction  with  the  third 
follows  directly  from  them.  (Compare  f.  146.)  Consequently,  in  writing 
the  symbol  of  any  plane  it  is  necessary  to  take  into  consideration  only 
the  vertical  axis,  and  two  of  the  lateral  axes  adjacent  to  each  other. 

The  various  holohedral  forms  possible  in  this  system  are  derived  after 
the  analogy  of  those  of  the  tetragonal  system.  The  parameters  for  all  the 
lateral  axes  are  given  below  for  sake  of  comparison.  It  is  to  be  noted  here 
that  m  may  be  either  <  1,  or  >  1  ;  n  is  always  >  1  and  <  2,  while  p  >  2 

and<  oo  ;  further  than  this  it  is  always  true  that  p— 


n 


Oc  :  a  :  a  :  (a) 

oo  c  :  a  :  a  :  (GO  a) 
oo  c  :  %a  :  a  :  (%a) 
oo  c  :  na  •  :  a  :  (pa) 
(  c  :  a  :  a  :  (oo  #) 
\  mo  :  a  :  a  :  (oo  a] 
mo  :  *2a  :  a  :  (2$) 
me  :  na  :  a  :  (  pa) 


n-l 

[(?]  when  m=0,    n=1. 

[/]  when  w=oo  ,  n—\. 

[-&-2]  when  m=oo  ,  n=2. 

fc  when  Tn  —  co  ,  n>\  and  <  2. 


[1] 
\m\ 


when  m=l     n= 
when  m 


m^l,  n=.\. 
[w-2]  when  m^.1,  n=-%. 
[m-n]  when  m^.1,  7^/1  and  <  2. 


The  abridged  symbols  need  no  explanation  beyond  that  which  has  been  given  on   p.  25  ; 
mPn—m-n  ;   <x>Pn=i-n,  etc. 

Basal  planes.  —  The  form   0=Qc  :  a  :  a  includes   the   two  basal  planes 
above  and  below,  parallel  to  the  plane  of  the  lateral  axes. 


144 


145 


146 


Prisms. — The  form  7=ooc  :  a  :  a  comprises  the  six  planes  parallel  to 
the  vertical  axis,  and  meeting  the  two  adjoining  lateral  axes  at  equal  dis- 
tances. These  six  planes  with  the  basal  plane  form  the  hexagonal  unit 
prism,  f.  14-i.  The  form  ^-2  =  ooc  :  2$  :  a  includes  the  six  planes  which 
are  parallel  to  the  vertical  axis  but  meet  one  of  the  lateral  axes  at  the  unit 
distance,  and  the  other  two  at  dmible  that  distance.  These  planes  with  the 
basal  plane  form  the  diagonal  prism,  f.  145.  The  relations  of  the  two 
prisms  /and  i-2  is  shown  in  f.  146.  In  f.  147,  it  will  be  seen  that  the  one 
prism  truncates  the  vertical  edges  of  the  other.  The  faces  of  the  i-2 
make  an  angle  of  150°  with  the  faces  of  7.  These  two  prisms  have  an  inti- 
mate connection  with  each  other,  and  together  form  a  regular  twelve-sided 
prism, — a  prism  which  is  crystallographically  impossible  except  as  the  result 
of  the  combination  of  these  two  different  forms. 


HEXAGONAL  SYSTEM. 


33 


The  form  i-2  is  a  special  case  of  the  general  form  i-n  or  oo  c  :  no, :  a. 
When  n  is  some  number  less  than  2,  and  greater  than  1,  there  must  be  two 
planes  answering  the  given  conditions  in  each  sectant,  and  twelve  in  all. 
Together  they  form  the  dihexagonal,  or  twelve -sided,  prism.  This  prism 
bevels  the  edges  of  the  prism  7,  and  the  vertical  edges  are  of  two  kinds, 
axial  and  diagonal.  The  values  of  n  must  lie  between  1  and  2  ;  some  of 
the  occurring  forms  are  &-J ,  ^-|>  etc. 

Hexagonal  pyramids,  or  Quartzoids. — The  symbol  1=<? :  a  :  a  belongs 
to  the  twelve  planes  of  the  unit  pyramid,  f.  148,  while  the  general  form 
m  —  rno  :  a  :  a  includes  all  the  pyramids  in  this  series  where  the  length  of 
the  vertical  axis  is  some  multiple  of  the  assumed  unit  length.  As  in  the 
tetragonal  system,  when  m  diminishes,  the  pyramids  become  more  and 
more  obtuse,  and  the  form  passes  into  the  basal  plane  when  m  is  zero ; 
while  as  m  increases,  the  pyramids  become  more  and  more  acute,  and  finally 
coincide  with  the  prism  /.  These  pyramids  consequently  replace  the  basal 
edges  between  O  and  7,  f .  149,  and  with  them  form  a  vertical  zone  of  planes. 

The  pyramids  of  the  m-2  series  have  the  same  relation  to  those  of  the  m 
series,  just  described,  that  the  prism  ?'-2  has  to  the  prism  I.  They  replace 
the  basal  edges  between  i-2  and  O  (f.  145),  and  as  the  value  of  m  varies, 
give  rise  to  a  series  or  zone  of  planes  between  these  limits. 

The  pyramids  of  both  the  first  (m)  and  the  second  (m-2)  series  are  well 
shown  in  f.  150,  of  apatite.  In  the  first  series  there  are  the  pyramids  -J,  1, 
and  2  ;  and  in  the  second  series  the  pyramids  1-2,  2-2,  and  4-2.  The  cor- 


149 


responding  prisms  /and  i-2  are  also  shown,  and  the  zones  between  each  of 
them  and  the  basal  plane  O  are  to  be  noticed.  Attention  may  also  be 
called  to  the  fact,  exemplified  here,  that  the  pyramid  2-2  truncates  the  ver- 
tical edges  of  the  pyramid  2  ;  also  1-2  truncates  the  vertical  edges  of  1 ; 
while  the  latter  form  (1)  also  truncates  the  vertical  ed^es  of  i-2,  as  is  seen 
inf.  147. 

^  Dihexagonal  pyramids,  or  Berylloids. — The  general  form  me  :  na  :  a 
gives  the  largest  number  of  similar  planes  possible  in  this  system,  which  is 
here  obviously  twenty-four,  that  is,  two  in  each  of  the  twelve  sectants. 
These  pyramids  correspond  to  the  prisms  of  the  i-n  series,  and  form  the 
dihexagonal  pyramids,  or  berylloids,  as  in  f.  151. 

The  berylloid  has  three  kinds  of  edges  :  the  axial  edges  X  (L  151,  152), 
connecting  the  apex  with  the  extremity  of  one  of  the  axes ;  the  diagonal 
edges  Y,  and  the  basal  edges  Z. 
3 


34 


CRYSTALLOGRAPHY. 


In  the  upper  pyramid,  one  of  these  two  planes  for  each  sectant  may  be 
distinguished  as  the  right,  and  the  other  the  left,  as  lettered  in  f.  152  ;  and 
the  same,  after  inverting  the  crystal,  for  those  of  the  other  pyramid.  It  is  to 
be  observed  that  in  a  given  position  of  the  form,  as  that  of  f.  151,  the  right 


151 


152 


153 


154 


W  /M 


of  the  upper  pyramid  will  be  over  the  left  of  the  lower  pyramid,  and  the 
reverse.  Fig.  153  represents  the  planes  of  such  a  form  m-n  combined  with 
the  unit  prism  /,  and  the  planes  are  lettered  I,  r,  in  accordance  with  the 
above.  In  f.  154,  of  a  crystal  of  beryl,  the  prism  /  is  combined  with  the 
pyramids  1,  2,  2-2,  and  the  berylloid  3-f. 


B.  Hemihedral  Forms. 

I.  VERTICALLY  DIRECT. — The  planes  of  the  upper  range  of  sectants  being 
in  the  same  vertical  zone  severally  with  those  below. 

(A).  Hemiholohedral. — Half   the   sectants  having  the  full  number  of 
planes : 

1.  Trigonal  pyramids. — The  diametral  pyramid  m-2  is  some-        155 
times  tlms  hemihedral,  as  in  the  annexed  figure  (f.  155)  of  a  crys- 
tal of  quartz,  in  which  there  are  only  three  planes,  2-2  at  each 
extremity,  and  each  of  those  above  is  in  the  same  zone  with  one 
below.     The  completed  form  would  be  an  equilateral  and  symme- 
trical double  three-sided  pyramid. 

2.  Trigonal  prisms. — The  occurrence  of  three  out  of  the  six 
planes  of  the  prism  /,  or  ^-2,  produces  a  three-sided  prism.     The 

is  thus  hemihedral  in  tourmaline  (f.  156,  a  top  view  of  a  crystal),  and  the 
prism  *-2  in  quartz.  Both  these  forms  properly  belong  to  the  Rhombo- 
liedral  division. 

3.  Ditrigonal  prisms. — An  hexagonal  prism  hemihedral  to  the  dihexago- 
nal  prism  occurs  in  quartz  and  tourmaline,  the  hexagonal  prism  sometimes 
having  only  the  alternate  vertical  edges  bevelled,  as  in  f.  183,  and  f.  185, 
p.  40. 

(B).  Holohemihedral. — All  the  sectants  having  half  the  full  number  of 
planes : 

1.  Hemi-dihexagonal  pyramids. — Each  sectant  has  one  out  of  the  two 
planes   of    the  dihexagonal  pyramid  (f.  151,  153) ;    this  is  indicated  by 


prism 


HEXAGONAL    SYSTEM. 


35 


the  shading  in  f.  157.     The  occurring  plane  may  be  the  right  above  and 
left   below,  or  left    above   and  right  below,   and  the  form  accordingly 


156 


157 


158 


Tourmaline. 


Apatite. 


either  rl  m-n,  or  IT  m-n.  Examples  of  the  first  of  these  occur  in  f.  158, 
representing  a  crystal  of  apatite,  the  planes  0(3-f),  and  o'(4c-£)  being  of 
this  kind.  This  method  of  hemihedrism  occurs  only  in  forms  that  are 
true  hexagonal,  and  not  in  the  rhombohedral  division. 

II.  VERTICALLY  ALTERNATE,  the  planes  of  the  upper  range  of  sectants 
being  in  zones  alternate  with  those  below. 

(A)  HemiholoJiedral  forms,  or  those  in  which  half  the  sectants  have  the 
full  number  of  planes  as  in  the 

RHOMBOHEDRAL  DIVISION. 

1.  RhoniboJiedrons,  and  their  relation  to  Hexagonal  forms. — The  rhom- 
bohedroii  is  derivable  from  the  hexagonal  pyramid  by  a  suppression  of  the 
alternate  planes  and  the  extension  of  the  others.  In  f.  159,  if  the  shaded 
planes  in  front  and  the  opposite  ones  behind  are  suppressed,  while  the  others 
are  extended,  a  rhombohedroii  will  be  derived.  This  is  further  shown 
in  f.  160,  where  the  hexagonal  pyramid  is  represented  within  the  rhom- 
bohedron.  Another  similar  rhombohedron,  complementary  to  this,  would 
result  from  the  suppression  of  the  other  alternate  half  of  the  planes.  One 
of  these  rhombohedrons  is  called  minus,  and  the  other  plus  (f.  161,  162). 
The  form  in  f.  148  is  made  up,  under  the  rhombohedral  system,  of  +& 
and  —R  (or  +1  and  —  1)  combined,  as  in  the  annexed  figure  (f.  163),  of  a 
crystal  of  quartz. 


Fig.  164  shows  the  combination  of  the  rhombohedron  with  the  prism  I\ 
in  f.  165  the  former  is  more  developed,  and  it  finally  passes  into  the  com- 


36 


CRYSTALLOGRAPHY. 


plete  rhombohedron,  f.  161.     In  f.  166  the  rhombohedral  planes  occur  on 
the  alternate  angles  of  the  diagonal  prism  i-%. 

The  symbol  of  the  unit  rhombohedron  as  referred  to  the  hexagonal  sys- 
tem is  -J-(c  :  a  :  a\  a  second  rhombohedron  may  be  i(2c  :  a  :  a)  and  so  on  ; 
it  is,  however,  more  simple  to  write  only  +  72  or  —72,  and  +  272  or  —272,  and 
so  on  ;  or,  where  there  is  no  confusion  with  the  symbols  of  hexagonal  forms, 
as  -hi.  —  1,  and  -\-m,  —m. 


163 


164 


Quartz. 


166 


168 


This  hemihedrism  resulting  in  the  rhombohedron  is  analogous,  in  the 
alternate  positions  of  the  planes  above  and  below,  to  that  producing  the 
tetrahedron  in  the  isometric  system.  But  owing  to  the  fact  that  there  are 
three  lateral  axes  instead  of  two,  the  rhombohedron  has  its  opposite  faces 
parallel,  unlike  the  tetrahedron. 

In  f.  167  the  planes  R  belong  to 
the  rhombohedron  +1 ;  f  to  the 
rhombohedron  +f,  having  the  verti- 
tical  axis  f  0  ;  O  is  the  basal  plane, 
or  mathematically  the  rhombohe- 
dron 0,  the  vertical  axis  being 
00.  I  is  the  hexagonal  prism 
oo  :  1  :  1,  or  more  properly  a  rliom- 
bohedron  with  an  infinite  axis,  co  c. 

s\        /     -2     ~j  /         \/\\       {  YJ    ^n  ^e  °PP08^e  side  of  I  the  planes 
^^r  V          V    \      \l/    are  rhombohedral,  but  belong  to  the 

minus  series ;  —  f  has  the  vertical 
axisf0;  —4.  40;  —2,  20  ;  —  f,  f-0, 
this  last  being  complementary  to 

+-§-,  and  the  same  identical  form,  except  that  all  the  parts 
are  reversed.  Fig.  168,  A-E  represent  different  rhombo- 
hedrons  of  the  species  calcite:  A.,  the  rhombohedron  1 ; 
7?,  — J-;  (7,  —2;  7>,  — f;  E,  4  ;  having  respectively  for 
the  vertical  axis,  Ic,  •£<?,  20,  -J0,  40,  with  0=0.8543,  the  lat- 
eral axes  being  made  equal  to  unity.  In  f.  169  the 
rhombohedron  2  (or  272)  is  combined  with  —1  (or  —72), 
the  latter  truncating  the  terminal  edges  of  the  former. 

In  relation  to  the  series  of  +  and  —  rhombohedrons  it 
is  important  to  note  that,  since  the  position  of  — ^72  is  that 
of  the  vertical   edge  of  +72,  in  combination    with  it,  it  truncates  these 
Similarly  +J72  truncates  the   same  edges  of  —  ^72,  and   so  on. 


Cinnabar. 


169 


Calcite. 


HEXAGONAL    SYSTEM. 


37 


Also  +  7?  truncates  the  edges  of  —27?,  and  —  R  the  edges  of  +  27?  (f.  169), 
—  27?  truncates  the  edges  of  +47?,  and  so  on. 

2.  Scalenohedrons  ;  forms  Jiemihedral  to  the  dihexagonal  pyramid. — As 
the  rhombohedron  is  a  hemihedral  hexagonal  pyramid  or  quartzoid,  so  a 
scalenohedron  is  a  hemihedral  dihexagonal  pyramid  or  berylloid.  rri*- 

j  1  T  P       1  «1  1        •  •  •  t  i  i  .  i  ^  *  "*  fe. 


method  of  hemihedrism  is  similar  by  the  suppression  of  the  planes  of  the 

ted  by  the  shading  in  f.  170  (analogous  to  f.  159) 


alternate  sectants,  as  indicated 

and  the  extension   of   those   of"  the 


<— '  \  o  / 

other   sectants.     A  scalenohedron  is 


173 


174 


represented  in  f.  171,  a  hexagonal  double  pyramid  with  a  zig-zag  basal  out- 
line, and  three  kinds  of  edges  ;  the  shorter  terminal  edge  X,  connecting  the 
apex  with  the  extremity  of  a  lateral  axis ;  the  longer  terminal  edge  Y, 
intermediate  in  position;  and  the  basal  edge  Z;  X  and  Y  correspond  to 
X  and  J^in  f.  151,152.  There  are  plus  and  minus  scalenohedrons,  as 
there  &re>phis  and  minus  rhombohedrons. 

The  relations  of  the  form  to  replacements  of  the  rhom- 
bohedron are  illustrated  in  the  other  figures.  Fig.  172  repre- 
sents a  rhombohedron  (+1  or  7?)  with  its  basal  edges  bevel- 
led ;  and  this  bevelment,  continued  to  the  obliteration  of  the 
planes  7?,  produces  the  scalenohedron  shown  by  the  dotted 
lines.  The  scalenohedron  in  f.  171,  172  has  the  vertical  axis 
equal  to  3c',  or  three  times  as  long  as  that  of  R,  the  lateral 
axes  of  both  being  equal ;  and  hence  it  is  that  the  planes  are 
lettered  I3,  the  1  referring  to  the  rhombohedron  and  the 
index  3  being  the  multiple  that  gives  the  value  of  the  vertical 
axis  of  the  scalenohedron. 

In  f.  113  there  are  two  scalenohedrons  of  the  same  series, 
viz.,  I5,  I3,  combined  with  the  rhombohedrons  7?  (or  +1)  and 
+  4.     Fig.  174  shows  the  scalenohedron  —  I3  combined  with 
the  rhombohedron  —4  (or  —47?);  and  175,  the  same  with  the  rhombohe- 
dron 5  (  +  5K). 

Other  scalenohedrons  replace  the  basal  angles  of  a  rhombohedron  by 
two  similar  planes  (f.  176)  ;  or  bevel  the  terminal  edges;  or  replace  the 
terminal  solid  angles  by  six  planes,  two  to  each  terminal  edge,  or  to  each 


38 


CRYSTALLOGRAPHY. 


rhombohedral  face  ;  and  they  will  be  relatively  +  or  — ,  according  to  their 
position  in  one  or  the  other  set  of  sectants,  as  has  been  explained.  Fig.  177 
represents  the  top  view  of  a  crystal  of  tourmaline.  It  contains  the  rhombo 


176 


177 


Tourmaline. 

hedral  planes,  jft,  |,  ~VS  ~ii~-J?  ~i>  —2,  along  with  the  scalenohedrons  — |-2, 
— yy  — -J&,  1|-,  I2,  and  also  two  others  bevelling  the  terminal  edges  of  the 
rhombohedron  •  R. 

The  scalenohedrons  — i2,  — |3,  — J5,  bevel  the  basal  edges  of  the  rhombohedron  — £;  and 
consequently  the  length  of  the  axes  are  respectively  2,  3,  5  times  that  of  the  rhombohedron 
£,  and  hence,  equal  lc,  f c,  fc-  Every  scalenohedron  corresponds  to  a  bevelment  of  the 
basal  edges  of  some  rhombohedron — and  that  particular  one  whose  lateral  edges  are  parallel 
to  those  of  the  scalenohedron.  The  symbols  for  them  accordingly  are  made  up  of  the 
symbol  of  the  rhombohedron  and  an  index  which  expresses  the  relation  of  its  vertical  axis 
as  to  length  to  that  of  the  rhombohedron,  according  to  a  method  proposed  by  JSaumann. 
(See  p.  72.) 

Hexagonal  pyramids  of  the  m-2  or  diagonal  series  occur  in 
many   rhombohedral  species  ;    as  f.  178  of  corundum,  which 
contains  f-2(r),  4-2,  -2/-2  (for  9-2  on  the  figure  read  %$-%,  Klein), 
along  with  the  rhombohedron  1,  and  the  basal  plane  0 ;   also 
f.  167,  in  which  is  the  pyramid  2-2.     Hemihedral  forms  of  the 
same  pyramids  (of  the  kind  described  on  p.  34)  are  met  with  in 
rhombohedral  species,  but  only  such  as  have  also  tetartohedral 
modifications.     Hemihedral  forms  of  the  hexagonal  and  dihex- 
Corundum.    agOna|  prisms  (p.  34.)  are  also  characteristic  of  some  rhombohedral 
species,  and  of  those  that  have  either  tetartohedral  or  hemimorphic  modifi- 
cations. 

Fig.  179  illustrates  the  relative  positions  of  the  zones  of 
the  +  and  —  rhombohedrons,  and  diagonal  pyramids  m-2 
alternating  with  regions  of  +  and  —  scalenohedrons  in  the 
scheme  of  the  rhombohedral  system.  The  figure  is  supposed 
to  be  a  top  view.  It  is  similar  to  f.  152,  p.  34,  and  like  that 
contains,  the  upper  planes  of  the  dihexagonal  pyramid  ;  but 
these  are  divided  between  a  plus  and  a  minus  scalenohedron, 
those  planes  marked  +  being  the  former,  and  the  others  (  — )  the 
latter.  The  three  lateral  axes  are  lettered  each  bb.  The  posi- 
tion of  the  +  mR  zone  of  planes  (or  plus  rhombohedrons)  relative 
to  the  scalenohedrons  is  shown  by  the  lettering  +7?;  of  the 
—mR  zones  (or  minus  rhombohedrons)  by  —  R.  The  position  of 
the  vertical  zone  of  w-2,  or  diametral  pyramidal  planes,  is 
indicated  by  the  letter  d.  The  order  of  succession,  beginning 
with  one  of  the  plus  interaxial  sectants  (the  one  in  the  medial  line  below)  and  numbering  it 
I,  is  as  follows : 


HEXAGONAL    SYSTEM. 


39 


f    (1)  Plus  scalenohedrons,  or  planes  of  the  general  form  +mn. 
I.  •<    (2)  Zone  of  plus  rhombohedrons,  -\-rnR. 

(    (3)  Plus  scalenohedrons,  or  planes  of  the  general  form  +mn. 

(4)  Zone  of  diagonal  pyramids,  ra-2. 

(    (5)  Minus  scalenohedrons,  or  planes  of  the  general  form  —  ma. 
II.  •<    (6)  Zone  of  minus  rhombohedrons,  —mR. 
(    (7)   Minus  scalenohedrons,  —  m". 

(8)  Zone  of  diagonal  pyramids,  w-2. 
C    (9)   Plus  scalenohedrons,  +mn. 
III.  -I  (10)  Zone  of  plus  rhombohedrons,  +mR. 
((11)    Plus  scalenohedrons,  +w". 
(12)  Zone  of  diagonal  pyramids. 

And  so  on  around,  as  the  figure  illustrates.  In  the  lower  pyramid  the  order  of  succession  is 
the  same  ;  but  the  plus  planes  are  directly  below  the  minus  of  the  above  view  of  the  upper 
pyramid. 

The  plus  scalenohedrons  have  the  pyramidal  edge  over  the  -\-rnR  section,  the  more 
obtuse  of  the  two  (or  edge  Y) ;  and  the  minus  scalenohedrons  have  that  edge  the  less  obtuse 
(or  edge  X),  and  that  over  the  —mR  section  the  more  obtuse  (or  edge  Y). 

B.  Holohemihedral  forms,  or  those  in  which  all  the  sectants  have  half 
the  full  ii umber  of  planes  (as  shown  by  the  shading  in  f.  180). 

Gyroidal,  or  trapezohedral  forms. — Of  the  planes,  in  f.  181  there  would 
occur  only  those  lettered  /*,  r,  above  and  below  ;  or  those  lettered  I,  I,  and, 
unlike  f.  157,  the  planes  above  and  below  are  not  in  the  same  zone.  The 


180 


181 


form  is  consequently  gyroidal,  the  planes  being  inclined  around  the  prism, 
both  above  and  below,  and  in  the  same  direction  at  the  two  extremities. 
It  is  also  called  plagihedral.  The  symbol  for  the  planes  is  rr  m-n,  or 
U  m-n,  according  as  the  occurring  planes  of  the  two  in  the  same  sector  are 
the  right  or  the  left.  Fig.  182  is  an  example  of  U  6-f  in  the  species  quartz. 


C.  Tetartofiedral  Forms. 

These  forms  are  hemihedral  to  the  Rhombohedron. 

(A)  Holomorphic forms,  like  the  preceding  hemihedral,  the  planes  occur- 
ring equally  in  the  upper  and  lower  range  of  sectants. 

1.  Rhombohedral  tetartohedrism. — Occurring  planes  the  alternate  of 
those  mentioned  on  page  35,  that  is,  the  alternate  planes  r  of  one  base, 
and  I  of  the  other.  They  are  the  r  of  three  alternate  sectants  above,  and 


CRYSTALLOGRAPHY. 


the  I  of  three  sectants  below  alternate  with  these.  A  form  of  this  kind 
consists  of  six  equal  planes,  equally  spaced,  and  hence,  equal  in  inclina- 
tions, and  is  therefore,  in  the  completed  state,  a  rhombohedron.  It  occurs 
in  menaccanite  or  titanic  iron,  and  in  quartz  (f.  183,  planes  13~Jf). 

2.  Gyroidal  or  trapezohedral  tetartohedrism. — Occurring  planes  the 
alternate  of  those  lettered  r  or  I  in  f.  153,  p.  34,  that  is,  the  alternate  planes 
r,  or  alternate  Z,  of  both  bases. 

183  184  185 


Quartz. 


Quartz. 


>  In  f.  185,  the  planes  o\  o",  om,  o{\  o*  (4-f,  5-|,  6-f,  8-f,  3-3,  the  first 
four  right,  the  last  left)  are  examples.  The  upper  and  lower  of  a  kind  adjoin 
the  same  diametral  plane,  but  are  on  opposite,  sides  of  it,  and  therefore  the 
three  sectants  containing  planes  below  are  alternate  with  the  three  above. 
The  solid  made  of  these  six  planes  (f.  184)  has  trapezoidal  faces,  and  is 
called  a  trigonotype  by  Naumann.  , 

The  tetartohedral  planes  on  quartz  and  cinnabar  have  a  remarkable  con- 
nection with  the  circular  polarization  which  is  characteristic  of  them 
both,  and  which  is  further  explained  elsewhere  (p.  138). 

(B)  Heinimorphio  forms ;  the  planes  occurring  either  in  the  upper  or 
the  lower  range  of  sectants  and  not  in  both. 

There  are  two  kinds  of  forms :  (1)  the  fiemi-rhom'bohedron,  and  (2)  the 
hemi-scalenohedron.  Fig.  186  illustrates  each  of  these 
forms.  The  form  R  is  properly  hemihedral  at  the  two 
extremities,  its  planes  being  very  large  at  one,  and 
quite  small  at  the  other.  So  with  —  J.  Another  rhom- 
bohedron, — 2,  occurs  only  at  the  upper  extremity. 
Again,  -J6  is  a  hemi-scalenohedron,  the  upper  six  planes 
being  present,  but  not  the  lower. 

The  prism  /in  this  figure  is  hemihedral,  as  explained 
9n  p.  34.  -It  is  not  tetartohedral  to  the  hexagonal 
system  in  the  ordinary  view.  But  since  in  a  vertical 
zone  +mR,  oo  R,  —mR,  the  oo  R  may  be  regarded  as 
the  infinite  term  of  either  the  +mR  series,  or  else  the 
same  of  the  —mR  series;  and  as  this  view  accords  with 
the  tetartohedral  character  of  the  mR  series  in  all  such 
cr\7stals,  it  might  be  ranked  among  tetartohedral  forms. 
From  the  same  point  of  view,  the  ditrigonal  prisms  in  tourmaline  and 


OKTHOKHOMBIC    SYSTEM.  .       41 

quartz  are  tetartohedral,  since  they  may  be  regarded  as  either  plus  or  minus 
tetartohedral  scalenohedrons,  with  an  infinite  vertical  axis. 

Variable  elements. — In  the  hexagonal  system  the  same  elements  are  vari- 
able as  in  the  tetragonal  (see  p.  30).  In  other  words,  the  position  of  the 
vertical  axis  is  fixed,  but  (1)  a  certain  length  must  be  assumed  as  the  unit 
in  a  given  species,  and  also  (2)  the  position  of  the  lateral  axes  must  be  fixed, 
for,  as  in  f.  144,  145,  either  of  the  hexagonal  prisms  may  be  made  I  and 
the  other  *-2. 

The  general  characteristics  of  this  system  which  the  student  must  be 
acquainted  with  are:  (1)  The  planes  constantly  occur  in  threes  or  sixes, 
or  their  multiples  ;  (2)  The  frequency  of  the  angles  120°  and  150°  in  the 
prismatic  series ;  (3)  The  rhombohedral  cleavage,  common  inr  species  be- 
longing to  the  rhombohedral  division.  It  is  also  important  to  note  that 
many  forms  apparently  hexagonal  really  belong  to  the  orthorhombic  system, 
being  produced  by  twinning  parallel  to  the  vertical  prism  ;  e.g.,  the  appar- 
ently hexagonal  prisms  of  aragonite.  The  close  relation  of  the  two  systems 
is  spoken  of  elsewhere  (p.  46). 

The  planes  of  symmetry  for  the  holohedral  forms  are  analogous  to  those 
in  the  tetragonal  system ;  that  is,  one  principal  plane  of  symmetry  normal 
to  the  vertical  axis,  and  six  others  intersecting  in  this  axis.  These  last 
belong  to  two  sets,  the  planes  of  the  one  cutting  each  other  at  angles  of 
60°,  and  diagonal  to  those  of  the  other. 


IY.—ORTHORHOMBIC  SYSTEM. 

In  the  ORTHOKHOMBJC  SYSTEM  the  three  axes  are  unequal  cy  b,  a ;  of  these 
c  is  the  vertical  axis,  b  is  made  the  longer  of  the  two  lateral  axes,  or  the 
maerodiagonal  axis,  and  a  the  shorter  lateral,  or  br  achy  diagonal,  axis.* 

The  different  occurring  forms,  deduced  as  before  from  the  general  ex- 
pression, are: 

me  \  nb  \  a  \m-n~\  \  oo  c  :  nb  :  a  [i-n\ 

me  :  b  :  na  \m-n\  \  oo  c  :  b  :  na  [i-n\ 

(mc:b:a  [m\  oo  c :  b  :  a  [/] 

(  c  :  b  :  a  [1]  oo  c  :  oo  b  :  a  [i-l~] 

j  me  :  oo  b  :  a  [m-i]  oo  c  :  b  :  oo  a  [i-i] 

(  me  :  b  :  oo  a  \m-l~]  Oe  :  b  :  a  [6>] 

The  abridged  symbols  need  very  little  explanation  additional  to  that  given  on  p.  25.  ^  As 
before,  only  the  essential  part  of  the  symbol  is  given  ;  ra  is  written  first,  and  refers  in  all 
cases  to  the  vertical  axis  (c),  and  n  refers  to  one  of  the  lateral  axes,  whether  the  longer  (b) 
or  the  shorter  (a)  is  indicated  by  the  sign  placed  over  it,  as  n  or  n.  When  n=cc  ,  this  is 
indicated  by  the  i  hitherto  used,  and  the  sign  is  placed  over  it,  *,  or  I,  with  the  same  signi- 
fication. These  correspond  to  the  symbols  used  by  Naumann,  as  follows:  0=OP;  i-\— 
oo  Poo  ;  i-i=<x>  Poo  ;  oo  P/l=i-n  ;  wPx>  =m-i ;  mP=  m ;  m-n=mP/~i,  etc. 


*  For  the  relation  of  the  axes  thus  lettered  to  those  of  Dana's  System  of  Mineralogy  and 
of  other  authors,  see  p.  53. 


CRYSTALLOGRAPHY. 


A.  HoloJiedrcbl  Forms. 

Pinacoids. — The  final  case  mentioned  in  the  above  enumeration  em- 
braces, as  before,  the  two  basal  planes,  or  basal  pinacoids:  tjie^ one  pre- 
ceding it  includes  the  two  planes  parallel  to  the  vertical  and  b^aei^-diagonal 
axes  (c  and  5),  called  the  macropinacoids,  and  the  third  includes  the  two 
planes  parallel  to  the  vertical  and  brachy diagonal  axes  (c  and  a),  called  the 
brachypinacoids.  These  three  sets  of  planes  together  form  the  solid  in 
f.  188,  which  is  called  the  diametral  prism.  In  consequence  of  the  ine- 
quality of  the  different  pairs  of  pfanes  there  are  only  four  similar  edges  in 
any  set;  thus  four  similar  vertical  edges  ;  four  macrodiagonal  basal  edges, 
two  above  and  two  below,  between  O  and  i-l ;  and  similarly  four  brachy- 
diagonal  basal  edges  between  0  and  i-l /  the  eight  solid  angles  are  all 
similar. 


187 


189 


Prisms.  —  The  form  oo  c  :  b  :  a,  or  /,  includes  the  four  planes  of  the  unit 
prism  which,  in  combination  with  0,  is  seen  in  f.  187.  In  this  case  the 
eight  basal  edges  are  similar,  being  made  in  each  case  by  a  sirm'lar  pair  of 
planes  O  and  I.  Of  the  vertical  edges  there  are  two  pairs,  those  at 
the_extremity  of  the  axis  a,  which  are  obtuse,  and  those  at  the  extremity 
of  bj  which  are  acute.  Similarly,  there  are  two  sets  of  basal  solid  angles, 
four  in  each;  for  though  each  solid  angle  is  formed  by  the  meeting  of 
the  same  three  planes,  the  angles  are  different  in  the  two  cases,  The 
form  /  replaces  the  four  similar  vertical  edges  of  f.  188  ;  the  macro- 
pinacoids i-l  truncate  the  obtuse  vertical  edges  of  the  prism  /,  and  the 
brachypinacoids  i-l  truncate  the  acute  vertical  edges  of  /,  as  shown  in  f.  189. 
There  are  two  other  series  of  prisms  with  symbols  oo  c  :  nb  :  a  and 
oo  c  :  1)  :  na.  In  the  latter  series  the  axis  b  is  made  the  unit  ;  the  reason  for 
this  will  be  obvious  when  the  relations  of  the  two  forms  are  explained. 

The  prism  I  meets  both  axes  a  and 
b  at  their  unit  lengths,  as  in  f.  187. 
If,  now,  the  prismatic  planes  meet 
the  longer  lateral  axis  (b)  at  a  greater 
distance,  a  prism  is  formed  such  as 
that  in  f.  190,  whose  symbol  is  is,  or 
GO  c  :  2b  :  a.  This  is  a  macrodiago- 
nal prism  ;  and  others  might  have 
the  symbols  i-l  (oo  c  :  $b  :  &),  i-1  (00  c  :  4&  :  &),  and  so  on,  or  in  general  i-n. 
If  n  becomes  less  than  unity,  the  case  shown  in  f.  191  arises,  where  the 
inner  prism  has  n=fa  and  the  symbol  is  i-~\  (oo  c  :  -J&  :  a\  still  retaining  a  as 
the  unit  axis.  For  convenience  of  reference,  however,  the  principle  before 
explained  (p.  11)  is  made  use  of,  and  the  plane  is  called  oo  c  :  b  :  2a,  or  i-&  ; 


190 


ORTHORHOMBIC    SYSTEM.  43 

these  expressions  and  those  before  given  being  identical,  except  that  in 
the  latter  case  b  is  the  unit  axis.  By  this  method  the  use  of  any  fractions 
less  than  unity  is  avoided.  The  inner  prism  ^-J,  indicated  by  dotted  lines 
in  f.  191,  then  becomes  the  outer  prism  or  i-2.  The  prisms  of  the  general 
form  i-n,  are  called  brachydiagonal  prisms. 

The  prisms  i-n  bevel  the  front  and  rear  (obtuse)  edges  of  the  prism  I, 
f.  192,  and  the  prisms  i-n  bevel  the  side  (acute)  edges  as  in  f.  193.  Further, 
the  former,  i-n,  replace  the  edges  between  i-l  and  /  (f.  194),  while  the  i-n 
prisms  replace  the  edges  between  i-t  and  1  (f.  194). 

This  series  of  planes  (f.  194),  from  i-l  to  i-l,  is  another  example  of  a 
zone ;  all  the  planes  make  parallel  intersections  with  each  other,  being  alike 
in  that  they  are  parallel  to  the  vertical  axis. 


192 


193 


194 

—  '       "     ~^> 

1 

12 

1 

Domes. — The  form  mo  :  oo  ~b  :  a  includes  the  four  planes  which  are 
parallel  to  the  macrodiagonal  axis,  and  meet  the  vertical  axis  at  variable 
distances,  multiples  of  the  unit  length  (see  f.  34,  p.  11).  An  example  of 
them  in  combination  with  i-l,  the  brachypinacoid,  is  shown  in  f.  195. 
These  planes  are  called  macrodomes  (see  also  f.  196). 


195 


196 


197 


The  forms  mo  :  b  :  oo  a  include  four  analogous  planes,  which  differ  in 
this  respect,  that  they  are  parallel  to  the  brachydiagonal  axis,  and  are  hence 
called  brachydomes  (see  f.  35,  p.  11).  In  this  case,  the  longer  lateral  axis 
is  taken  as  the  unit.  Fig.  197  shows  two  such  brachy  domes,  14  arid  24, 
in  combination  with  other  forms.  (See  also  f .  198.)  The  word  dome,  used 
here  and  above,  is  derived  from  So//,?;,  or  doinus,  a  house,  the  form  resem- 
bling the  roof  of  a  house. 

The  combination  of  14  with  14  is  shown  in  f.  199,  forming  a  retangular 
octahedron,  and  in  f.  200  they  are  shown  replacing  the  solid  angles  formed 
by  I  and  O,  as  in  f.  188.  As  either  of  the  three  directions  may  be  made 
the  vertical,  it  is  evident  that  these  domes  differ  from  vertical  prisms  only 
in  position. 


44 


CRYSTALLOGRAPHY. 


200 


The  occurrence  of  these  domes  in  combination  with  the  other  forms,  0, 
j  i-%,  I,  affords  an  illustration  of  the  law  of  symmetry  that   all  similar 

parts  must  be  modified  alike.  Thus  in  f. 
188,  as  has  been  shown,  there  are  two  sets 
of  solid  angles,  four  in  each ;  one  set  is 
replaced  by  the  four  planes  of  the  form 
m-i,  and  if  one  is,  all  must  be ;  and  the 
other  set  (lateral)  is  replaced  by  the  four 
planes  of  the  form  m-i,  f.  200. 

Octahedrons  (or  Pyramids). — The  sym- 
bol c  :  b  :  a  (1)  belongs  to  the  unit  octahedron  (f.  201).  It  replaces  the 
edges  between  the  prism  /and  the  basal  plane  0  (f.  202).  It  also  replaces 


201 


202 


203 


the  eight  similar  solid  angles  of  the  diametral  prism,  as  in  f.  203.  This 
is  a  special  case  of  the  form  me  :  b  :  a,  in  which  m  may  have  values  vary- 
ing from  0  to  oo  .  Fig.  208,  of  sulphur,  shows  a  zone  of  such  planes,  of 
the  general  symbol  me  :  b  :  a,  with  m=oo  for  /;  also,  w=l,  ?/2/=i,  w=J, 
m—^  and  finally  m=0,  for  the  basal  plane  O. 


204 


205 

,4c 


206 


207 


The  general  form  in  this  system,  consisting  of  eight  similar  planes,  may 
be  written  either  me  :  nb  :  a  (m-n)  or  me  :  o  :  na  (m-ft).  The  relation  be- 
tween the  two  is  the  same  as  that  between  the  prisms  i-n  and  i-n.  Thus, 
in  f.  204,  one  plane  of  the  octahedron  2c  :  2&  :  a  (2-2)  is  given,  and  also  one 
plane  of  another  octahedron  or  pyramid,  whose  Symbol  is  2c  :  1)  :  a  (2).  If 
n  becomes  less  than  unity,  as  -J,  the  plane  has  the  symbol  2<?  :  ^b  :  a  (2-J). 
In  order  to  avoid  this  use  of  fractions  the  symbol  is  written  4c  :  b  :  2«, 
that  is,  4-2.  The  plane  is  shown  in  f.  205,  in  its  two  positions  correspond- 
ing to  20  :  $>  :  <z,  and  4c  :  b  :  2a,  the  two  being  crystallographically  iden- 
tical. 


OETHOKIIOMBIC    SYSTEM. 


45 


Thus  there  are  two  series  of  pyramidal  planes  :  a  macrodiagonal  (m-n\ 
where  the  shorter  axis  is  taken  as  the  unit,  and  a 
brachy diagonal  (m-n)*  where  the  unit  is  the  longer 
lateral   axis;   and  between  the  two  lie  the  unit 
octahedron  (1)  and  those  of  the  m  series,  just 


as 


the  prism  /  lies  between  the  prisms  i-n  and  i-n. 
The  macrodiagonal  planes  1-2  and  2-2  are  shown 
in  f.  206  and  f.  207.  It  is  also  seen  in  f.  207  that 
the  planes  2-2,  L'4,  2-2  all  make  parallel  intersec- 
tions with  each  other  and  with  i-$,  being  an 
example  of  a  zone  where  the  ratios  of  the  ver- 
tical axes  are  the  same.  Further  orthorhombic 
forms  are  displayed  in  f.  208,  of  sulphur,  already 
referred  to.  The  full  symbol  of  the  plane  1-3  is 
c  :  b  :  3a. 

B.  Hemihedral  Forms. 


Sulphur. 


The  hemihedral  forms  that  have  been  observed  are  of  two  kinds :  1, 
The  vertically -oblique  (p.  14),  producing  monodinic  forms;  and  2,  the 
hemimorphic,  in  which  the  planes  of  the  octahedrons  or  domes  of  one  base 
have  no  corresponding  planes  at  the  opposite  extremity.  The  former  kind 


209 


211 


Humite. 


Humite. 


Calamine. 


is  illustrated  in  f.  209,  of  the  species  chondrodite  (var.  humite,  type  III). 
Fig.  210  represents  the  holohedral  form  of  the  same  ;  the  planes  |4,  14, 
24,  are  of  macrodomes  ;  ^4,  £4,  |4,  44,  of  brachydomes  ;  and  the  others  of 
various  octahedrons,  mostly  in  two  vertical  zones,  the  unit  zone  (me  :  b  :  a), 
and  the  1  :  2  zone  (ma  :  2b  :  a).  In  f.  209  the  alternate  of  the  macro- 
domes  and  of  the  octahedral  planes  of  the  1  :  2  zone  are  absent  in  the 
upper  half  of  the  form,  and  are  present  without  those  with  which  they 
alternate  in  the  lower  half.  The  crystal  consequently  resembles  one  under 
the  monoclinic  system. 

Datolite  was  formerly  cited  as  a  hemihedral  orthorhombic  species,  but  it 
has  been  found  to  be  really  monoclinic.  Furthermore,  it  has  been  recently 
shown  by  the  author,  by  reference  to  the  optical  properties,  that  the  chon- 


46  CRYSTALLOGRAPHY. 

drodite  of  the  second  and  third  types  (see  p.  305)  is  not  orthorhombic  but 
monoclinic,  and  this  must  be  true  also  of  humite.* 

Hemiraorphic  forms  characterize  the  species  topaz  and  calamine.  The 
latter  (in  f.  211)  has  only  the  planes  of  a  hemioctahedron  at  one  extremity, 
and  planes  of  hemidomes  at  the  other.  For  the  pyro-electric  properties  of 
such  forms,  see  p.  165. 

Variable  elements. — In  the  orthorhombic  system  the  lengths  of  the  three 
axes  are  variable,  though  their  position  is  fixed,  and  after  these  are  fixed 
the  choice  of  one  for  the  vertical  axis  must  be  arbitrarily  made.  In  other 
words,  given  an  orthorhombic  crystal,  the  three  rectangular  directions  are 
fixed,  but  two  assumptions  must  be  made  which  will  mathematically  deter- 
mine the  length  of  two  of  the  axes  in  terms  of  the  third.  For  instance, 
in  a  crystal,  if  certain  occurring  domes  are  adopted  as  the  unit  planes  ~L-l 
and  l-£,  this  will  determine  the  relative  lengths  of  the  three  axes,  for 
which  two  measurements  will  be  necessary  ;  or,  if  an  occurring  octahe-. 
dron  is  assumed  as  the  unit  octahedron  (1,)  this  alone  will  obviously  fix  the 
axes;  but  here,  also,  two  independent  measurements  are  necessary  in  order 
to  enable  us  to  calculate  their  length,  as  is  explained  later,  p.  74.  Hav- 
ing determined  upon  the  relative  lengths  of  the  axes,  one  of  these  must  be 
made  the  vertical  axis  (c),  and  then,  of  the  two  remaining,  the  shorter  will 
be  the  brachy diagonal  (a),  and  the  longer  the  macrodiagonal  axis  (&). 

In  deciding  these  arbitrary  points,  the  following  serve  as  guides  :  The 
habit  of  the  crystals;  the  relations  of  the  given  species  to  those  allied  in 
composition;  the  cleavage,  which  is  regarded  as  pointing  to  that  form 
which  is  properly  fundamental ;  and  other  considerations.  How  arbitrary 
the  choice  generally  is  is  well  shown  by  the  fact  that,  in  a  considerable 
number  of  species  belonging  to  this  system,  different  lengths  of  axes,  as 
also  different  positions  for  them,  have  been  adopted  by  different  authors. 
"Where  an  optical  examination  can  be  made  of  an  orthorhombic  crystal, 
the  results  show  what  the  true  position  of  the  axes  is,  in  accordance  with 
the  principles  proposed  by  Schrauf.  This  subject  is  alluded  to  again  in  its 
proper  place  (p.  147). 

The  general  characteristics  of  the  crystals  of  this  system  are  not  so 
marked  as  those  of  the  preceding  systems.  The  kind  of  symmetry  should 
be  well  understood,  though,  as  remarked  on  p.  50,  crystals  which  are  in 
appearance  orthorhombic"  may  be  really  monoclinic ;  the  true  test  of  the 
system  is  to  be  found  in  the  three  rectangular  axial  directions.  A  pris- 
matic habit  is  very  common,  the  prisms  (except  the  diametral  prism)  not 
being  square,  also  the  prominence  of  some  of  the  most  commonly  occur- 
ring macrodornes  and  brachydomes ;  a  prismatic  cleavage  is  common, 
and  often  a  cleavage  exists  parallel  to  one  of  the  pinacoids  (e.g.,  i-l) 
and  not  to  the  other,  which  could  not  be  true  in  the  tetragonal  system  ; 
similarly  the  planes  i-l,  i-l  are  sometimes  physically  different,  e.g.,  in 
regard  to  lustre. 

As  has  already  been  remarked,  forms  apparently  hexagonal  are  common 
among  certain  species  belonging  to  this  system  ;  this  is  true  in  those  cases 

*  Since  the  above  paragraph  was  put  into  type,  Des  Cloizeaux  has  announced  that  an  opti- 
cal investigation  by  him  has  proved  that  humite  crystals,  of  types  II.  and  III.,  are  really 
monoclinic,  as  suggested  above.  The  figures  are  allowed  to  remain,  however,  since  they  illus- 
trate the  form  which  this  method  of  hemihedrism  would  produce. 


MONOCLINIC    SYSTEM. 


47 


the  prism  has  an  angle  approximating  to  120°.     It  is  immediately 
t,  as  is  explained  more   thoroughly   in  the  chapter   on    compound 


where 

evident, 

crystals,  that  if  three  individual  crystals  are  united  each  by  a  prismatic 

face,  when   the   prismatic   angle   is   near-  120°,  they  will  form   together 

a  six-sided  prism,  approximating  more  or  less  closely  to  a  regular  hexa- 

gonal prism.     Similarly,  under  the  same   circumstances,  the  correspond- 

ing pyramids  will  thus  together  form  a  more  or  less  symmetrical  hexagonal 

pyramid.      This  is  illustrated  by  the  accompanying 

figures  of  witherite,  where  the  prismatic  angle  is  118°, 

3u'.     It   need  hardly   be   added  that  this   is  true  in 

general,  not  only  of  the  vertical  prism,  but  also  of  a 

macrodome  or  brachydome,  having  an  angle  near  120°. 

The  optical  relations  connected  with  this  subject  are 

alluded  to  elsewhere,  p.  147. 

Planes  of  Symmetry.  —  The  three  diametral  planes 
are  planes  of  symmetry  in  this  system,  and  they  are  the  only  ones. 


V._ MOISTOCLINIC   SYSTEM. 

In  the  MONOCLTNIC  SYSTEM  the  three  axes  are  un- 
equal in  length,  and  while  two  of  them  have  rectan- 
gular intersections,  the  third  is  oblique.  The  position 
usually  adopted  for  these  axes  is  as  shown  in  f.  214, 
where  the  vertical  axis,  c,  and  lateral  axis,  &,  make 
retangular  intersections,  The  same  is  true  of  b  and 
dj  while  c  and  d  are  oblique  to  one  another. 

The  following  is  an  enumeration  of  the  several 
distinct  forms  possible  in  this  system,  deduced,  as  be- 
fore, from  the  general  expression  : 


—m-n 
+  m-n 
—m-n 
-f-  ?n-n 
[-m] 

[-1] 
[+»»] 

[  +  1] 


214 


—me  :  oo  b  :  a 

\—m 

•fl 

+  me  :  GO  b  :  a 

\_+m 

oo  c  :  nb  :  a 

[i-n 

]/ 

oo  c  :  b  :  na 

[i-n 

oo  c    b  :  a 

{f 

oo  c    oo  b  :  a 
oo  c    b  :  oo  a 

Si-i' 
i-l~ 

Oe:b:a 

\o\ 

— mo  :  nb  :  a 

-\-rne  :  nb  :  a 
j  —  mo  :  b  :  na 
(  +  mc  :  b  :  na 
j  —me  :  b  :  a 
(  —e  :  b  :  a 
(  +mc  :  b  :  a 
\  +c  :  b  :  a 

me  :  b  :  <x>  a 


The  abridged  symbols  correspond  to  those  in  the  orthorhombic  system,  explained  on  p.  42. 
The  only  point  to  be  noted  is  that  where  n  or  i  relates  to  the  clinodiagonal  axis,  d,  this  is 
indicated  by  an  accent  placed  over  it,  as  m-i,  m-n  ;  but  in  m-i,  and  m-n,  etc. ,  *  and  n  refer 
to  the  orthodiagonal  axis.  -Naumaim  wrote  these  mPao ,  and  mPn,  or  else  with  the 
accent  across  the  initial  letter  P.  The  minus  signs  are  used  in  the  same  way  as  by  Naumann 
(see  p.  76). 

Pinacoids. — As  in  the  orthorhombic  system,  there  are  three  pairs  of 
pinacoidal  planes :  the  base  0=0c  :  b  :  a\  the  orthopinacoid,  parallel  to  the 


48 


CRYSTALLOGRAPHY. 


216 


ortho-axis  (J)  co  c  :  oo  b  :  a,  or  i-i ;  and  the  dinopinacoid,  parallel  to  the  in- 
clined axis  (d)y  oo  c  :  b  :  oo  a,  or  i-i. 

In  the  solid  (f.  216)  or  diametral  prism  formed  of  these  three  pairs  of 
planeo,  the  four  vertical  edges  are  similar,  and  this  is  also  true  of  tlie  four 
edges  between  O  and  i-i.  On  the  other  hand,  the  four  remaining  edges  are 
of  two  sets ;  that  is,  the  edge  in  front  above  is  similar  to  the  edge  be- 
hind and  below,  for  the  angles  are  equal 
and  inclosed  by  similar  planes ;  but  these 
edges  are  not  similar  to  the  remaining 
two.  since,  though  the  planes  are  the 
same,  the  inclosed  angles  are  unequal  to 
the  former.  Further,  there  are  two  sets 
of  solid  angles,  two  in  front  and  two  dia- 
gonally opposite  behind,  being  alike  ob- 
tuse angles,  and  the  other  four  alike  and  acute. 

Prisms. — In  consequence  of  the  similarity  of  the  vertical  edges  of  the 
diametral  prism,  they  must  all  be  replaced  if  one  is  ;  this  is  done  by  the 

unit  prism  /(oo  c  :  l>  :  #),  in  f.  215,  217. 

Of  the  other  prisms,  each  obviously  consist- 
ing of  four  planes,  there  are  two  series,  the 
orthodiagonal,  i-n,  and  clinodiagonal,  i-ii, 
bearing  the  same  relation  to  each  other  as 
the  macro-  and  brachy-diagonal  prisms  in 
the  orthorhombic  system,  in  fact,  the  same 
explanation  may  be  made  use  of  here.  Fig. 
217,  of  a  crystal  of  datolite  from  Toggiarra, 
shows  the  pinacoid  planes,  as  also  the  unit 
prism,  Z,  and  the  clinodiagonal  prism,  i-5. 

Clinodomes. — The  form  m-i  (me  :  b  :  oo  a) 
includes  the  four  planes  parallel  to  the  clino- 
diagonal axis,  and  meeting  the  others  at  variable  distances.  They  are  analo- 
gous to  the  braehydomes  of  the  orthorhombic  system.  There  are  four  of 
these  planes,  because  the  two  axes,  c  and  &,  make  rectangular  intersections. 
This  is  also  seen  in  f.  218,  since,  as  has  been  remarked,  the  four  clino- 
diagonal edges  in  f.  215  are  similar,  and  hence  are  simultaneously  replaced 
by.  these  clinodomes. 

218 


Orthodomes. — Of  the  general  form,  mo  :  oo  b  :  a,  there  are  two  sets  of 
planes,  two  in  each,  both  of  which  are  alike  in  that  they  are  parallel  to  the 
vertical  (c)  and  orthodiagonal  (b)  axes  (see  f.  219).  They  are  unlike,  how 
ever,  in  that  two  are  opposite  an  obtuse  angle,  and  two  opposite  the  acute 
angle.  Consequently  these  two  pairs  of  planes  are  distinct,  and  must  occuJ 


MONOCLINIO    SYSTEM. 


independently  of  each  other.  To  distinguish  between  them,  those  belonging 
to  the  obtuse  sectants  receive  the  minus  sign(— m-i\  and  those  belonging 
to  the  acute  sectants  the  plus  sign  (4-m-^),  f.  219.  This  same  point  is  illus- 
trated by  f.  220,  where,  as  has  been  remarked,  the  obtuse  edges,  above  in 


221 


222 


front,  and  below  behind,  are  similar,  and  are  hence  replaced  by  planes  of 
the  —niri  series,  while  the  remaining  two  (f.  221),  are  also  similar,  and  are 
replaced  by  +m-i  planes. 

Hemi-octahedrons. — The  same  distinction  of  plus  and  minus  belongs  to 
all  the  pyramidal  planes,  and  the  signs  are  used  in  the  same  way.  For 
each  form  there  are  only  four  similar  planes. 

The  m  series  is  that  of  the  unit  octahedrons,— properly  hemi-octahe- 
drons,  or  hemi-pyramids  +m  and  —  m.  The  form  made  up  of  +1  and  — 1 
is  seen  in  f .  223,  and  in  f .  222  the  same  planes  are  in  combination  with  the 
three  pinacoids. 

The  general  form,  +m-n,  —m-n,  and  +m-n,  —  m-n,  give  each  four  simi- 
lar planes.  They  bear  exactly  the  same  relation  to  each  other  as  the  m-n 
and  m-n  of  the  orthorhombic  system,  so  that  no  additional  explanation  is 
needed  here  in  regard  to  them. 

The  figure  (f.  217)  of  datolite  may  be  referred  to  for  illustrations  of  the 
different  forms  which  have  been  named.  There  are  here  three  different 
clinodomes  |-^,  24,  and  4-i,  each  comprising  four  planes  ;  a  minus  hemi- 
orthodome  (opposite  the  obtuse  angle),  —2-*,  and  also  a  plus  orthodome, 
H-2-a  (these  two  planes  are  quite  distinct,  though  numerically  the  symbols  are 
the  same) ;  moreover,  of  hemi-octahedrons  of  the  unit  series,  there  are  —  4, 
— f,  and  +4,  +2,  +f,  +  l,  +  -g-,  +f;  also  of  orthodiagonal  pyramids,  —4-2,- 
—  6-3,  also  +2-2,  and  of  clinodiagonal  planes,  — 8-£,  and  +12-J-.  A 
careful  study  of  a  few  such  figures,  especially  with  the  help  of  models,  will 
give  the  student  a  clear  idea  of  the  symmetry  of  this  system.  It  will  be 
noticed  that  all  the  planes  above  in  front  are  repeated  below  behind,  and 
those  below  in  front  appear  again  above  behind.  More  important  than 
this,  it  will  be  seen  that  the  clinodiagonal  diametral  plane  divides  the  crys- 
tal into  two  symmetrical  halves,  right  and  left;  in  other  words,  as  remarked 
later,  it  is  a  plane  of  symmetry. 

Hemihedral  forms  occur  of  a  hemimorphic  character,  in  which  the  planes 
about  the  opposite  extremities  of  the  orthodiagonal  axis  are  unlike  a  plane 
of.  one  or  more  hemi-pyramids  occurring  at  one,  without  that  corresponding 
at  the  other,  as  in  tartaric  acid,  ammonium  tartrate,  etc. 

With  many  monoclinic  crystals  the  obliquity  is  obvious  at  sight ;  but  with 
many  others  it  is  slight,  and  can  be  determined  only  by  exact  measurements. 


50 


CRYSTALLOGRAPHY. 


In/datolite  it  is  only  six  minutes.  The  character  of  the  symmetry  exhibits 
further  the  obliquity.  But,  as  seen  above,  both  H-  and  —  planes  of  the  same 
value  do  occur  together,  and 'though  they  are  really  distinct  yet  they  may 
give  a  monoclinic  crystal  the  aspect  of  an  orthorhombic  crystal.  On  the 
other  hand,  true  orthorhombic  crystals  may  be  hemihedral,  and  thus  may  be 
monoclinic  in  the  character  of  the  symmetry  (p.  45). 

Variable  elements. — In  the  monoclinic  system,  the  only  element  which  is 
fixed  is  the  position  of  the  orthodiagonal  axis  (b)  at  right  angles  to  the  plane 
in  which  the  other  axes  must  lie.  The  lengths  of  these  axes  must  obviously 
be  assumed  in  the  same  way  as  in  the  preceding  system ;  but,  further  than 
this,  their  position  in  the  given  plane,  and  the  angle  they  make  with  each 
other,  are  both  arbitrary ;  in  other  words,  any  plane  in  the  zone  at  right 
angles  to  the  clinopinacoid  may  be  taken  as  the  base  (O)  and  any  other 
as  the  orthopinacoid  (i-i).  The  existence  of  a  prismatic  cleavage,  or  one 
parallel  to  a  plane  in  the  orthodiagonal-  zone  often  points  to  the  planes  which 
are  really  to  be  considered  fundamental.  In  many  cases  it  is  considered 
desirable  to  assume  an  angle  near  90°  as  the  angle  of  obliquity,  so  as  to  show 
the  degree  of  divergence  from  the  rectangular  type.  It  need  hardly  be 
added  that  authorities  differ  widely  both  as  to  the  position  and  lengths 
given  to  the  axes  of  the  same  species. 

Plane  of  symmetry. — Monoclinic  crystals  have  but  one  plane  of  sym- 
metry, the  diametral  plane,  in  which  the  vertical  and  clinodiagonal  axes 
lie,  that  is,  the  plane  parallel  to  the  clinopinacoids.  The  maximum  num- 
ber of  similar  planes  for  any  form  is  four,  and  it  will  be  noticed  that 
there  is  no  single  form  which  alone  can  enclose  a  space,  or  form  a  geome- 
trical solid. 


VI.— TEICLINIC  SYSTEM. 

In  the  TRICLINIC  SYSTEM  the  three  axes  are  unequal,  and  their  intersections 
are  mutually  oblique.  In  consequence  of  this  fact,  there  is  no  plane  of 
symmetry.  Only  diagonally  opposite  octants  are  similar ;  there  can  conse- 
quently be  only  two  planes  of  any  one  kind.  There  are  no  truncations  or 
bevelments,  and  no  Intel-facial  angles  of  90°,  135°,  or  120°.  The  prisms 
are  all  hemiprisms,  and  the  octahedrons  tetarto-octahedrons. 

The  lateral  axes  are  called  the  macrodiagonal  (b),  and  the  ~br  achy  diago- 
nal (a).  In  f .  225  the  diametral  prism  (made  up  of  three  pairs  of  different 


228 


planes)  is  represented,  and  in  f .  224  the  unit  prism.  To  the  latter  is  added 
(in  f.  226)  one  plane  —1  on  two  diagonally  opposite  edges,  which  are  two 
out  of  the  eight  of  the  unit  octahedron  (f.  227).  This  octahedron,  as  will 


MATHEMATICAL    CEYSTALLOGEAPHY.  51 

be  seen,  is  made  up  of  four  sets  of  different  planes.  The  different  kinds 
of  planes  are  distinguished  by  the  long  or  short  mark  over  the  n  (n  or  #) 
and  also  by  giving  those  which  occur  in  the  right-hand  octants,  in  front, 
an  accent ;  those  above  (in  the  obtuse  octants)  are  minus,  and  the  others 
plus.  The  form  m-n  consequently  may  be  —m-n',  or  —  m-n,  -\-m-n ,  or 
-\-m-n ;  and  similarly  with  m-n.  In  f.  228  the  unit  prism  is  combined  with 
a  hemidome  and  a  vertical  plane  parallel  to  the  brachy diagonal  section. 

The  forms,  although  oblique  in  every  direction,   may  still  be  closely 
similar  to  monoclinic  forms  of  related  species. 


Anorthite.  Axinite. 

The  annexed  figures  are  of  triclinic  species.  In  f .  229,  of  anorthite,  of 
the  feldspar  group,  the  form  is  very  similar  to  those  of  the  monoclinic 
feldspar,  orthoclase  ;  in  orthoclase,  O  on  the  brachy  diagonal  (clinodiagonal) 
section  is  90°,  whence  it  is  monoclinic,  while  in  anorthite  this  angle  is  85° 
•60',  or  4°  10'  from  90°,  and  this  is  the  principal  source  of  the  diversity  of 
angle  and  form. 

Fig.  230  represents  one  of  the  crystalline  forms  of  axinite,  nearly  all  of 
which  fail  of  any  special  monoclinic  nabit. 


MATHEMATICAL  CEYSTALLOGEAPHY. 

Introductory  remarks  on  the  proper  symbol  of  each  plane  of  a  general 
crystalline  form. — Hitherto  the  symbol  me  :  nb  :  a  has  been  employed  to 
express  the  general  position  of  all  the  planes  comprising  any  crystalline 
form,  and  it  has  been  shown  that  there  are  in  some  cases  forty-eight  similar 
planes  answering  to  the  general  symbol,  and  in  other  cases  only  two.  En 
order,  however,  to  express  the  exact  position  of  each  individual  plane  be- 
longing to  such  a  form,  it  becomes  necessary  to  resort  to  the  methods  of 
analytical  geometry.  As  shown  in  f.  231,  the  portions  of  the  axes,  when 
the  centre  is  the  starting  point,  which  lie  above,  to  the  right,  and  in  front 
of  the  centre,  are  called  plus  (+) ;  the  corresponding  portions  of  the  axes 
measured  from  the  centre  below,  to  the  left,  and  behind,  are  called,  for  the 


52 


CRYSTALLOGRAPHY. 


sake  of  distinction,  minus  (— ).  The  planes  of  the  first  quadrant  (see  also 
f.  232)  are  all  positive  (4-);  the  planes  of  the  second  positive  (+)  with 
reference  to  the  axes  c  and  #,  but  negative  (— )  with  reference  to  b ;  in  the 


231 


232 


third,  both  lateral  axes  are  negative  (—  )  ;  in  the  fourth  quadrant  the  planes 
are  positive  in  regard  to  c  and  &,  but  negative  with  respect  to  a.  The 
lower  quadrants  are  respectively  similar,  except  that  the  vertical  axis  is 
always  negative.  The  symbols  for  each  plane  of  the  orthorhombic 
octahedron  (f.  231),  taken  in  the  same  order,  will  be  as  follows  . 


Above,  +c  :  -f  b  : 
Below,  —  c  :  +  b  : 


;  +c  :  —b  :  -\-a\   +c  :  —b  :  —  a\  +c  :  +  b  :  —a. 
;  —  c  :  —b  :  +  «;  —  c  :  —b  :  —a\  —c  :  +b  :  —a. 


The  hexoctahedron  (ma  :  na  :  a)  may  be  taken  as  another  example.  The 
general  symbol  of  the  form  of  f.  247,  p.  64,  is  3-f  (3a  :  fa  :  a\  but  the 
symbol  of  each  plane  is  distinct.  The  same  principle  applies  here  as  in  the 
other  case.  Several  of  the  planes  in  f.  247  are  numbered  to  allow  of 
convenient  reference  to  them  as  examples,  the  appropriate  symbols  are 
written  below;  the  order  in  the  symbols  is  the  same  as  that  uniformly  used 
in  the  work  :  1st,  the  vertical  axis  (c)  ;  2d,  the  lateral  axis  extending  right 
and  left  (b)  ;  and  3d,  the  lateral  axis,  in  front  and  behind  (a). 


c       b       a 

1  —  3a  :  f  a  :    a 

2  =  f  a  :  3a  :    a 

3  =    a  :  3a:  %a 

4  =    a  :  f  a  :  3a 

5  =  4$  :    a  :  3a 


c  b     a 

6  =      3a  :        a  :  f  $ 

7  =  —  3a  :      f  a  :    a 

8  =  —  3a  :        a  :  %a 

9  —      %a :  —3a  :    a 

10  =  —  3a  :  —%a  :    a,  and  so  on. 


It  will  be  evident  from  these  examples  that  to  express  the  position  of 
an  individual  plane  the  numbers  expressing  its  relations  to  the  three  axes 
must  all  be  regarded,  each  with  its  appropriate  sign ;  in  other  words,  the 
values  of  m,  n,  r,  in  the  general  form,  me  :  nb  :  ra,  must  all  be  given,  one 
of  them  being  unity;  m  always  refers  to  the  vertical  axis,  c;  n  to  the 
lateral  axis,  b ;  r  to  the  lateral  axis,  a ;  as  has  already  been  remarked,  a 
is  usually  made  the  unit  axis.  In  the  example  last  given  the  axes,  being 
all  equal,  are  all  called  a. 


MATHEMATICAL    CRYSTALLOGRAPHY.  53 

Reference  must  be  made  here  to  the  method  of  lettering  the  axes  adopted  in  this  work. 
The  usage  of  the  majority  of  authors  is  followed,  and  the  subject  is  illustrated  in  the  fol- 
lowing table. 

Isometric. 

Common  usage.  ) 

This  work        [•         a 

(Weiss,  Rose.)  ) 
Miller's  School, 
Mohs,  Naumann,  a 

Dana  (System  1868)     a 


Tetrag.  (Hexag.)          Orthorhombic,  Triclinic. 
vert.          lat.        vert,    macrodiag.  brachydiag. 


Monoclinic. 
vert,  orthodiag.  clinodiag. 


It  is  certainly  very  desirable  to  indicate  to  which  axis  each  letter  refers  by   the  mark 
placed  above  it ;  in  doing  which,  we  follow  Klein's  Einleitung  in  dieKrystallberechnung. 


DETERMINATION    OF   PLANES   BY    ZONES. 

The  subject  of  zones  has  been  briefly  explained  on  page  4,  and  various 
examples  have  been  pointed  out.  The  principle  is  one  of  the  highest  im- 
portance, both  practically,  since  it  gives  the  means  of  determining  the 
symbols  of  many  planes  without  calculation,  and  also  theoretically.  The 
Itw  of  zones,  which  states  simply  that  the  planes  of  a  crystal  lie  in  zones, 
is  one  of  the  most  important  of  the  science,  and  second  only  to  that  of  the 
rationality  of  the  indices.  The  planes  of  a  crystal  thus  may  be  said  to  be 
connected  together  by  tliese  zones,  a  single  plane  often  lying  in  a  large 
number  of  zones. 

Parallelism  in  the  combination  edges,  or  mutual  intersections  of  planes, 
is  based  upon  some  common  geometrical  ratio,  and  this  common  ratio  be- 
longs to  the  symbols  of  all  the  planes  of  the  zone. 

233 

All  planes  which  lie  in  the  same  zone  will  give  exactly 
parallel  reflections  with  the  reflective  goniometer,  as  explained 
on  p.  87.  This  is  the  only  decisive  test,  and  when  possible 
should  be  made  use  of,  since  combination-edges  often  appear 
parallel  when  the  planes  forming  them  are  not  really  in  the 
same  zone.  Furthermore,  inasmuch  as  parallel  intersections 
are  observed  between  planes  of  a  zone  only  when  they  actually 
intersect,  the  goniometer  may  often  serve  to  detect  the  ex- 
istence of  zones  not  otherwise  manifest. 

Iii  f.  194,  p.  45,  the  planes  i-i,  *-2,  /,  £-5,  ££,  all 
lie  in  a  vertical  zone,  and  they  are  all  obviously 
alike  in  this,  that  they  are  parallel  to  the  vertical 
axis  ;  in  other  words,  the  common  value  c  =  GO  be- 
longs to  them  all.  Again,  in  the  zone  O,  14,  2-£,  Acanthite. 
i-i,  etc.  (f.  197,  p.  43),  the  planes  are  alike  in  that 

they  are  all  parallel  to  the  brachydiagonal  axis  ;  in  other  words,  a  =  oo  is 
true  of  all  of  them.  Still  again,  the  pyramidal  planes  i,  1,  2  (f.  150,  p.  33), 
are  also  in  a  zone  between  O  and  /,  and  here  the  ratio  1  :  1  for  the  lateral 
axes  applies  to  all ;  also,  1-2,  2-2,  4-2,  are  in  a  zone  from  O  to  a-2,  and  for 
them  the  lateral  axes  have  the  ratio  1:2.  In  the  case  of  an  oblique  zone, 
as  i-$,  3-3,  2-2,  1,  etc.  (f.  233),  this  fact  is  less  evident  on  inspection,  but  is 
equally  true,  as  will  be  seen  later.  The  common  ratio  in  this  case  is  m  =  r. 

Since  all  the  planes  of  a  zone  have  a   common  ratio,  which  has  been 


54  CRYSTALLOGRAPHY. 

shown  to  be  true  in  several  examples  but  also  admits  of  rigid  proof, 
it  is  evident  that  a  plane  which  lies  in  two  zones  has  its  position  deter- 
mined by  that  fact,  since  it  must  answer  to  two  known  conditions.  In 
other  words,  the  algebraic  equation  of  a  zone  is  known  when  the  parame- 
ters of  two  of  its  planes  are  given,  for  they  are  sufficient  to  determine  the 
common  ratio,  and  by  combining  them  the  zone  equation  is  obtained ;  and 
further,  when  the  equations  of  two  zones  are  given,  combining  them  will 
give  the  equation,  that  is,  the  parameters,  of  the  plane  common  to  both. 

The  general  equation,  derived  from  Analytical  Geometry,  for  any  plane 
me  :  nb  :  ra,  making  parallel  intersections  with  the  planes  m'c  :  nfb  :  r'a 
and  m"c  :  n"~b  :  r"a  is, 

M       N      R 

—  -j +  _  —  Q  .  m  which, 

m         n         r 

M=  m'm"(nfTr/-n"r'}\  N=  n'n"  (r'm"-r"ml);  R  =  r'r"  (mW-m'W). 

By  substituting  the  values  of  the  parameters  of  two  given  planes  for  m' , 
n' ',  r'9  and  m",  n'1 ',  r"  in  the  zone  equation,  a  derived  equation  is  obtained 
which  expresses  the  relations  between  m,  n,  r  of  all  the  planes  of  the  zone. 
The  form  of  the  general  zone  equation  is  so  symmetrical  that  the  calcula- 
tions are  in  any  case  quickly  and  easily  made  by  a  method  analogous  to 
that  used  in  Miller's  system  (as  suggested  by  Prof.  J.  P.  Cooke).  If  we 
write  the  parameters  in  parallel  lines,  repeating  'the  first  two  terms,  we 
have 


n 


m"  ,  n"    ^   »>" 


V/ 

X\ 


and  it  will  be  seen  that  the  coefficients  M,  N,  R  are  found  by  multiplying 
together  the  parameters  in  the  manner  which  the  scheme  indicates. 

M  =  m'm"  (n'r"-r'n").  N=  n'n"  (r'm"-m'r").  R  =  r'r"  (m'n"-n'm"\ 

Take,  for  example,  the  zone  of  planes  between  i4  and  1  (f.  233).  For 
i4,  m'  =  i,  n'  =  1,  r'  =  i  ;  for  1,  m"  =  1,  n"  =  1,  T"  =  1  ( i  =  oo  ) ;  hence 
the  scheme  becomes 

i  '  l   V    i    V  i    V   1 
1  ,  1   /\    1   /\   1    X\   1 

and  for  the  several  values  of  the  coefficients 

M=  i  (1  -  i)  =  -  v*.    jy=l  (i-i)  =0.    R  =  i  (i  -  1)  =  &. 

This  reduces  the  zone  equation  to  m  =  r  (after  dividing  by  i2  =  oo 2),  and 
tojhis  all  the  planes  of  the  zone  conform.  So  also  for  the  zone  of  1-1,  7, 
3-f,  14,  etc.,  in  f.  234.  The  parameters  of  the  plane  /  and  14  arranged  as 
above  give 

.^11^1 
1     i     1     1     * 

and  the  values  of  M,  N,  R  are  —  &  —i,  and  +^  respectively.     Hence  the 
zone  equation  becomes 

I     1     L 

m         n         r          ' 


MATHEMATICAL    CRYSTALLOGRAPHY. 


55 


and  if  r  —  1,  the  general  formula  n  =  — — r  is  derived.  Between  ^  :  I:  1  (/) 
and  1  :  *  :  1  (14)  the  values  of  n  are  positive,  as  with  the  series  of  planes 

2:2:1;  f  :  3  : 1,  etc!,  1  :  i:  1.'  Between  1  ~\i  :  1  234 
and  \  the  values  of  n  are  negative,  that  is,  are 
measured  on  the  back  half  of  the  axis  & ;  as,  for 
example,  f  :  _  4  :  1 ;  f  :  -  3  :  1 ;  f  :  -  2  :  1  ;  £ : 
—  1:1.  As  the  zone  continues  on  from  -|  :  —1:1 
to  1 :  -  1  :  ±i  (1-2),  and  i:  -1 :  -1  (/),  the  unit 
axis  is  changed,  making  n  •=.  — 1.  The  zone  equa- 
tion then  becomes  r  = 7.  the  values  of  r  beino; 

m— 1' 

positive  between  -J  :  —  1  :  1  and  1  :  —  1  :  ±  i,  and 
negative  between  1  :  —  1 :  ±  i  and  i  :  —  1  :  —1. 
The  successive  planes  are  f  :  —  1  :  2  ;  f  :  — 1:3; 
|:-i:4;  1  :  -1 :  ±  i  ;  i:-l:-4;  f:_l:_3;  a  :  -1 

Both  figures  233  and  234  are  illustrations  of  this  zone. 


-2,  etc. 


If  the  student  will  select  a  variety  of  examples  of  zones  from  the  figures  in  the  descriptive 
part  of  this  work,  and  will  apply  the  zone  equation  as  given  above  to  them,  paying  special 
attention  to  the  signs  of  the  parameters  of  each  plane,  he  will  soon  find  that  the  apparent 
difficulties  of  the  subject  disappear. 

EXHIBITION  OF   THE  ZONE-RELATIONS  OF   DIFFERENT   PLANES  BY  MEANS  OF    METHODS   OF 

PROJECTION. 

The  relations  of  the  different  planes  of  a  crystal  are  to  some  extent  exhi- 
bited graphically  in  such  figures  as  have  been  already  given.  Other  meth- 
ods, however,  are  used  which  have  special  advantages.  The  two  most 
important  are  briefly  mentioned  here. 

1.  Quenstedtfs  method  of  projection. — In  this  method  the  planes  of  a 
crystal  are  projected  upon  a  horizontal  plane,  usually 
that  of  the  base  (0).  Every  plane  is  regarded  as  pass- 
ing through  the  unit-length  of  the  axis  which  is  taken 
as  the  vertical ;  these  planes  consequently  appear  as 
straight  lines  intersecting  each  other  on  the  plane  of 
projection. 

The  following  are  examples.  In  f .  235,  of  galenite, 
there  are  present  the  planes  of  the  cube,  octahedron, 
dodecahedron,  and  tetragonal  trisoctahedron  f-f .  In 
the  projection  (f.  236)  the  plane  of  the  paper  is  taken 
as  that  of  the  cubic  plane,  the  two  equal  lateral  axes  (a) 
are  shown  in  the  dotted  lines,  and  the  vertical  axis  is  perpendicular  to  the 
plane  of  the  paper  at  their  point  of  intersection.  Any  arbitrary  length  of 
the  lateral  axes,  as  ca,  is  taken  as  the  unit.  One  of  the  cubic  planes  coin- 
cides with  the  plane  of  the  paper,  and  the  others,  since  they  are  supposed 
to  pass  through  the  unit  point  of  the  vertical  axis,  coincide  with  the  projec- 
tions of  the  lateral  axes,  and  are  marked  JS,  H. 

The  octahedral  planes  (1)  appear  as  lines  connecting  the  unit  lengths  of 
the  equal  lateral  axes  ;  of  the  dodecahedral  planes,  four  pass  each  through 


56 


CRYSTALLOGRAPHY. 


the  extremity  of  one  lateral  axis,  and  parallel  to  the  other,  and  four  others 
are  diagonal  lines  passing  through  the  centre ;  they  are  marked  i  in  the 
tigure.  "  The  other  planes,  f -f ,  when  passing  through  the  unit  point  of  the 
vertical  axis,  are  represented  by  the  symbols  1  :  f  :  1,  and  1  :  1 :  f ,  and 
1  :  f  :  f ,  in  the  first  quadrant,  and  similarly  in  the  other  three. 


237 


The  projection  of  the  first  of  these  planes  is  the  line  joining  the  points  x 
(ex  =  -f-  of  c#J)and  a?  ;  that  of  the  second  plane  is  the  line  joining  the  points 
a}  and  y  (cy  =  f  of  cct?) ;  that  of  the  third  plane  is  the  line  joining  the  points 
zl  and  22  (czl  =  cz'  _-  f  of  GO).  The  same  method  is  followed  in  the  other 
quadrants,  the  twelve  lines,  lightly  drawn,  in  the  figure  are  the  projections 
of  the  twelve  corresponding  planes  of  the  form  3-J. 

Fig.  237.  238,  give  another  example  (topaz)  from 
the  orthorhombic  system.  The  dotted  lines,  as  before 
(f.  238),  show  the  lateral  axes  on  which  the  relative 
unit  lengths  of  b  and  a  belonging  to  this  species  have 
been  marked  oft  (b  =  1.892,  &  =  1).  The  four  lines 
passing  through  these  unit  points,  a  and  Z»,  are  the  pro- 
jections of  the  unit  octahedron  1.  The  unit  prism,  /, 
is  projected  in  lines  parallel  to  these,  and  passing 
through  the  centre.  The  prism  a-2  also  passes  through 
the  centre,  but  the  direction  is  that  of  a  line  joining 
the  unit  length  of  the  axis  b  with  two  times  that  of  d. 
The  symbol  of  the  octahedron  f  (  —  Jc  :  b  :  a),  becomes, 
on  supposing  the  plane  to  pass  through  the  unit  point 
of  the  vertical  axis  c  :  f  b  :  f«,  and  it  is  consequently  projected  in  the  lines 


MATHEMATICAL    CRYSTALLOGRAPHY. 


joining  the  points  t  (ct  —  f  of  c5),  and  s  (cs  =  f  of  c«).  The  symbol  of  the 
plane  f -2  (=  jj-c1  :  5  :  20)  becomes,  on  the  same  condition,  c  :  \b  :  $a,  and  its 
projection  lines  consequently  connect  the  points  t  (ct  =  f  of  cb)  and  n  (cu 
—  f  of  c«).  The  same  method  is  followed  in  the  other  systems ;  in  the 
hexagonal  there  are  on  the  plane  of  projection  three  equal  lateral  axes 
cutting  each  other  at  angles  of  60°. 


238 


It  will  be  seen  from  these  examples  that  planes  in  a  zone  all  pass 
through  the  same  point  of  intersection;  as  in  f.  234,  (9,  f-f,  1,  *(#2),  and, 
f.  237,  /,  *-2,  i-i  (c) ;  this  is  also  true  mathematically  of  the  planes  O,  1,  f , 
/,  whose  projections  are  parallel.  This  principle,  which  follows  immediately 
from  the  fact  stated  above  that  planes  in  a  zone  have  a  common  ratio  for  two 
of  the  axes,  is  very  important.  If  a  given  plane  lie  in  two  zones  its  projection 
must  necessarily  pass  through  the  two  points  of  intersections  which  belong 
to  each  of  these  respectively,  and  consequently  its  position  is  determined. 
The  plane  on  f.  237  which  has  no  written  symbol  for  instance,  lying  in 
the  zone  with  f  and  f ,  and  the  zone  with  1  and  -jj-2,  must,  when  projected, 
pass  through  the  intersection  point  (f.  238)  s  of  the  former  zone,  and  also 
through  v  that  of  the  second  zone.  The  plane  itself,  then,  is  one  which 
meets  the  vertical  axis  at  its  unit  length,  the  axis  b  obviously  at  an  infinite 
distance,  and  the  axis  a  at  a  distance  f  of  its  unit  length  ;  hence,  the  sym- 
bol is  c  :  oo  b  :  •§•#,  or  \G  :  oo  b  :  a  (f -*)  in  the  form  it  is  usually  written.  In 
many  cases  the  ratios  of  the  lateral  axes  are  obvious  at  sight,  as  here  ;  in 
every  case,  however,  the  position  of  the  zonal  point,  and  of  the  two  points 
of  intersection  011  the  axes,  admits  of  exact  determination  by  a  series  of 
simple  equations. 

These  equations  it  is  unnecessary  to  add  here ;  reference  for  them  may 
be  made  to  Quenstedt's  Crystallography,  or  that  of  Klein,  mentioned  on 
p.  59.  This  method  is  of  so  general  use  and  of  so  easy  application  that 
every  student  should  be  familiar  with  it.  Its  advantages  are  that 'it  leads 
to  a  clearer  comprehension  of  the  relations  of  the  different  forms,  showing 
immediately  all  the  zones  in  which  they  lie,  and  in  many  cases — without  the 


58 


CRYSTALLOGRAPHY. 


use  of  equations — suffices  to  determine  the  symbols  of  an  unknown  plane, 
and  that  more  simply  than  by  the  use  of  the  zonal  equation.  The  general 
principles  contained  in  the  method  have  been  made  by  its  proposer  (Quen- 
stedt)  the  basis  of  an  ingenious  and  philosophical  system  of  Crystallography 
(Grundriss  der  bestimmenden  und  rechnenden  Krystallographie  von  Fr. 
Aug.  Quenstedt,  Tubingen,  1873). 

2.  Spherical  projection  of  Neumann  and  Miller. — In  this  subject,  as 
viewed  by  Miller,  a  crystal  is  situated  within  a  sphere  so  that  the  centres  of 
the  two  coincide.  If  now  perpendiculars,  or  normals,  be  drawn  from  this 
centre  to  each  plane,  and  be  produced,  they  will  meet  the  surface  of  the 
sphere,  and  these  normal  points  will  determine  the  position  of  each  plane. 
If,  then,  this  sphere  is  regarded  as  projected  upon  a  horizontal  plane  it  will 
appear  as  a  circle,  and  the  various  normal  points  will  occupy  each  its  pro- 
per position  on  or  within  this  circle.  This  will  be  made  more  clear  by  an 
example.  If  the  crystal  (f.  237)  be  supposed  to  occupy  the  centre  of  a 
sphere,  and  if  the  terminal  plane  coincide  with  the  plane  of  the  paper,  a 
normal  to  the  plane  O  will  meet  the  sphere  of  projection  at  the  central 
point  (f.  239) ;  the  planes  i-l  at  the  points  indicated,  and  so  of  the  other 

planes  1 ,  f ,  i-2,  etc. 

Two  principles  here  are  of 
fundamental  importance :  1st,  all 
planes  of  a  zone  have  their  nor- 
mals in  the  same  great  circle,  as 
i-i,  f ,  |4,  etc. ;  and  2d,  the  an- 
gles between  these  normal  points 
are  the  supplements  of  the  an- 
gles between  the  actual  planes. 
These  having  been  stated,  it  will 
be  clear  at  once  that  the  calcula- 
tion of  the  angles  between  dif- 
ferent planes,  i.e.,  their  normals, 
becomes  merely  a  matter  of  solv- 
ing a  series  of  spherical  triangles 
in  which  some  parts  are  given 
and  others  obtained  by  calcula- 
tion. Upon  this  basis  a  system 
of  crystallography  was  construct- 
ed by  Miller  in  1839,  which,  as  further  developed  by  Grailich,  Schrauf, 
von  Lang  and  Maskelyne,  has  every  advantage  over  that  of  Naumann 
in  the  matter  of  facility  of  calculation  as  in  some  other  even  more  import- 
ant respects. 

The  method  of  construction  of  the  circle  of  projection,  for  a  given  crystal,  is  in  most  cases 
very  simple.  The  position  of  the  crystal  is  commonly  so  taken  that  the  prismatic  zone  is 
represented  by  the  circumference  of  the"  circle,  and  the  position  of  the  normal-points  of  all 
prismatic  planes  lie  upon  it.  The  normal-points  of  the  pinacoid  planes  are  at  90°  from  one 
another  (the  macropinacoid  is  not  present  on  the  crystal,  f.  237).  The  two  corresponding 
diameters,  at  right  angles  to  each  other,  which  are  properly  the  projections  of  two  great  cir- 
cles, intersect  at  the  centre  the  normal-point  of  the  basal  plane,  0  ;  these  diameters  repre- 
sent respectively  the  macrodome  (m-T)  and  brachydome  (m-i)  zones  of  planes.  The  several 
positions  of  the  normal-points  of  the  prismatic  planes  are  determined  by  laying  off  the  sup- 
plement angles  of  each  with  a  protractor  ;  that  of  i-%  is  43°  25',  and  of  /,  62°  8^',  from  the 


MATHEMATICAL   CRYSTALLOGRAPHY.  59 

normal-point  of  i-i.  The  lines  drawn  between  £-2,  0,  and  £-2  (behind),  and  7,  0,  /"(behind) 
represent  the  zones  of  the  m-%  and  m  pyramids  respectively.  The  position  of  the  normal- 
points  of  a  dome  or  pyramid  upon  its  respective  zonal  line  (great  circle)  is  formed  by  laying 
off  from  the  centre  a  distance  equal  to  the  tangent  of  half  the  supplement  angle  of  the  given 
plane  on  0,  taking  the  radius  as  unity.  For  example,  0  A  \-l  —  126°  27',  hence  the  position 
of  the  required  normal-point  will  be  about  £  (.5046)  of  the  radius  measured  from  0. 

It  is  in  general  necessary  to  determine  in  this  way  the  normal-points  of  but  very  few  of 
the  planes,  since  those  of  the  others  are  given  by  the  zonal  connection  between  the  planes. 
Thus  in  this  case,  having  determined  in  the  way  explained  the  positions  of  the  points  i-i,  £-2, 
/,  and  |4,  no  further  calculation  is  needed;  the  point  of  intersection  of  the  great  circle 
joining  i-i.  f-1,  and  i-i,  and  that  joining/,  0,  /,  is  the  normal- point  of  f ;  also  the  point  of 
intersection  of  the  great  circle  £-2,  f4,  £2  with  7,  0,  /,  is  the  normal-point  of  1,  and  with 
»-2,  0,  *-2  that  of  1-1 

The  method  explained  is  the  sanre  for  all  the  orthometrio.  systems  ;  for  the  clinometric  sys- 
tems the  same  principle  is  made  use  of,  though  che  application  is  not  quite  so  simple,  since 
the  basal  plane  does  not  fall  at  the  centre  of  the  circle. 

In  the  system  of  Miller  the  general  form  of  the  symbol  is  Jikl,  in  which  h,  It,,  and  I  are 
always  whole  numbers,  and,  the  reciprocals  of  Naumann's  symbols.  To  translate  the  latter 
into  the  former  it  is  only  necessary  to  take  the  reciprocals  and  reduce  the  result  to  three 
whole  numbers  and  write  them  in  the  proper  order.  In  general,  for  m-n  (me  :  nb  :  a), 
h  :  k  :  I  =  mn  :  m  :  n,  the  latter  expression  being  written  in  its  simplest  form,  and,  if  neces- 
sary, fractional  forms  must  be  reduced  to  whole  numbers  by  multiplication.  Conversely, 

from  Jikl  is  obtained  m=  -,  n  =     ,   and  hence,  —  —  —  =  m-n.     This  applies  to  all  the  sys- 
l  K  Ik, 

terns  except  the  hexagonal,  where  a  special  process  is  required.     See  Appendix  (p.  399). 

METHODS  OF  CALCULATION. 

In  mathematical  crystallography  there  are  three  problems  requiring 
solution :  1st,  The  determination  of  the  elements  of  the  crystallization  of 
a  species,  that  is,  the  lengths  and  mutual  inclination  of  the  axes ;  2d,  The 
determination  of  the  mutual  interfacial  angles  of  like  or  unlike  known 
planes  ;  and  3d,  The  determination  of  the  symbols,  that  is,  values  of  the 
parameters  m  and  n  for  unknown  planes. 

This  whole  subject  has  been  exhaustively  discussed  by  Naumann  in  his  several  works  on 
crystallography.  (For  titles,  see  p.  iv.)  The  long  series  of  formulas  deduced  by  him  cover 
almost  every  case  which  can  arise.  In  the  present  place  the  matter  is  treated  briefly,  since 
for  all  ordinary  problems  in  crystallogfaphy  the  amount  of  mathematics  required  is  very 
small.  This  is  especially  true  in  view  of  the  fact  that  a  large  part  of  unknown  planes  can 
be  determined  by  the  zonal  equation  already  given.  When  complicated  problems  do  arise, 
the  methods  of  spherical  trigonometry  (based  on  the  spherical  projection  of  Miller)  offer,  in 
the  opinion  of  most  crystallographers,  the  simplest  and  shortest  mode  of  solution.  It  is  be- 
lieved that  the  student  who  has  mastered  the  elements  of  the  subject,  after  the  method  of 
Naumann  here  followed,  will,  if  he  desire  to  go  further,  find  it  to  his  advantage  to  turn  to  the 
system  of  Miller,  referred  to  on  p.  58  (See  also  Appendix.)  The  formulas  given  under 
the  different  systems  in  the  following  pages  are  mostly  those  of  Naumann,  and  it  has  been 
deemed  desirable  to  explain  at  length,  in  most  cases,  the  methods  by  which  these  formulas 
are  deduced.  If  the  student  will  follow  these  explanations  through,  he  will  find  himself  in 
a  position  to  solve  more  difficult  problems  involving  similar  methods.  Spherical  triangles 
are  employed  in  most  cases,  as  early  used  by  Hausmann  (1813),  by  Naumann  (1829),  and 
others  ;  and  carefully  explained  by  Von  Kobell  in  1867  (Zur  Berechnung  der  Krystallformen). 
The  same  methods  have  been  elaborated  by  Klein  (Einleitung  in  die  Krystallberechnung, 
Stuttgart,  1875). 

THE  RATIO  OP  THE  TANGENTS  IN  BECTANGULAR  ZONES. 

Tangent  principle. — In  any  rectangular  zone  of  planes,  that  is,  a  zone 
lying  between  two  planes  at  right  angles  to  each  other,  one  of  them  being 
a  diametral  plane,  the  tangents  of  the  supplement  angles  made  with  this 


(50 


CRYSTALLOGRAPHY. 


240 


diametral  plane  are  proportional  to  the  lengths  of  the  axis  corresponding 
to  it. 

Examples  of  rectangular  zones  are  afforded  by  the  zones  between  i-i  and 
i-i,  also  /  and  O,  f.  130,  and  /  and  O,  in  f.  208';  still  again  between  /  and 
O,  in  f.  167 ;  /  and  O,  also  £-2  and  0,  in  f .  150.  In  f .  217,  the  zone  be- 
tween i-i  and  i-\  and  0  and  i-i,  as  also  the  zones  between  i-i  and  any  one  of 
the  orthodomes,  are  rectangular  zones,  but  not  the  zones  between  the  basal 
and  vertical  planes  (except  i-i),  nor  those  between  i-i  and  a  clinodome. 
The  truth  of  the  above  law  is  evident  from  the  accompanying  figures. 
If  the  angles  between  the  planes  el,  &,  ez  (f.  240)  and 
the  basal  plane  O  are  given,  their  supplements  are  the 
angles  with  the  basal  diametral  section  a1,  a2,  a3,  respec- 
tively (f.  241).  The  tangents  of  these  angles  are  the 
respective  lengths  of  the  vertical  axis,  corresponding 
to  each  plane,  as  seen  in  the  successive  triangles.  In 
each  case  we  have  b  tan  a  =  c,  and  hence,  tan  a1  :  tan 
a2  :  tan  a3  =  cl  :  c2 :  c3. 

By  the  law  stated  on  p.  10,  the  ratio  of  the  axes  must 
have  some  simple  numerical  value.  In  other  words,  if 
cl  be  taken  as  the  unit,  c2  and  c3  must  bear  some  simple 
ratio  to  it  (denoted  generally  by  m).  In  general,  if  a1, 
a2,  a3  are  the  supplement  angles  of  three  planes  of  a 
vertical  zone  upon  a  basal  plane,  then, 


tan  a1  :  tan  a2  :  tan  a3  =  mlc  : 


m 


This  is  true  as  well  for  the  pyramidal  planes  p1,  p2,  jt?3, 
and  the  domes  dl,  d2,  d?  (f.  240).  This  principle  is 
most  commonly  applied  to  a  vertical  zone,  where  the 
angles  on  the  basal  plane  are  known,  and  the  value  of 
m  for  each  is  required  ;  it  applies,  however,  in  the  same 
way,  to  any  rectangular  zone. 

For  a  prismatic  zone,  if  the  supplement  angles  on  i-i 
are  given  =  »/,  T2,  etc.,  then, 

tan  71  :  tan  T2 :  tan  7s  =  51  :  b2  :  &3  =  nl  :  n2  :  ri*. 

These  relations  may  perhaps  be  made  more  clear  by  a  little  further 
explanation.     Suppose  a  plane  to  pass  through  the  vertical  axis  at 
right  angles  to  the  given  zone  0,  e1,  e2,  e3,  and  intersecting  it  in  the 
dotted  line  (see  also  f.  241).     A  similar  section  may  be  made  with  the 
planes  rf1,  d*,  d? ,  or  with  p1,  p\  p5.     From  the  section  (f.  241),  the 
900 •-•! W    relation  of  the  vertical  axes  to  the  tangents  of  the  basal  angles  is  at 
i       once  obvious.     It  will  be  seen  here  that  a1,  a2,  etc.,  are  not  only  the 
supplements  of  the   interfacial  angles  measured  on  0,  but  are  also 

equal  to  the  angles  measured  on  i-i  diminished  by  90°,  and  this  is  true  in  general.     It  will 
be  also   seen   that   the   angles   a1,  a2,  etc.,  may   be  obtained  from   the  angles  of  the  planes 


measured  on  each  other.     Thus,  given  el  A  0  =  180"—  a1,  and  given 
plement  of  <?2A  0)  —  a1  +  (180°  —  el  A  A 


p 
2,  obviously  a2  (sup 


USE   OF    SPHERICAL   TRIGONOMETRY. 


The  use  of  a  spherical  triangle  often  simplifies  very  much  the  operation 


MATHEMATICAL   CRYSTALLOGRAPHY.  61 

of  calculating  the  various  angles  and  axial  ratios.  The  following  example 
will  exemplify  the  principle  involved.  Fig.  242  represents  a  square  octa- 
hedron of  zircon.  If  we  take  the  front 
solid  angle  of  the  octahedron  as  a  cen- 
tre, and  from  it  imagine  three  arcs  to 
be  described  with  any  radius — one  on 
the  octahedral  plane  BA,  another  on 
the  basal  section  CA,  and  a  third  on 
the  diametral  section  CB,  it  is  evi- 
dent that  a  spherical  triangle  will  be 
formed.  In  other  words,  the  point  a 


is   imagined   to   be   the    centre   of   a 


sphere  and  the  triangle  ABC  is  that 
portion  of  its  surface  included  between  the  three  planes  in  question. 
In  this  triangle  (f.  243)  the  successive  parts  are  as  follows  : 

C  —  the  angle  between  the   basal  and  vertical  diametral   sections  ; 

here  90°. 

a  =.  the  inclination  of  the  vertical  edge  on  the  lateral  axis. 
B '=  the  semi-vertical  angle  of  the  octahedron  (=  \X\ 
h  (the  liypothenuse)  =  the  plane  angle  of  the  octahedral  face. 
A  —  the  semi-basal  angle  (=  ^Z). 
b  —  the  inclination  "of  the  basal  edge  on  the  lateral  axis. 

In  the  case  given,  ~b  =  45°,  since  in  this,  the  tetragonal  system,  the 
lateral  axes  are  equal  and  the  basal  edge  makes  an  angle  of  45°  with  each. 
Now  if  either  A  or  B  (that  is,  JTor  Z)  is  given  by  measurement,  two  parts 
in  the  triangle  will  be  known  and  the  others  can  be  rea  lily  calculated  as 
they  may  be  required.  Other  examples  will  be  found  in  the  pages  which 
follow. 


In  the  majority  of  cases  the  spherical  triangles  obtained  in  the  manner  described  are 
right-angled,  and  the  problems  resolve  themselves  into  the  solution  of  right-angled  spherical 
triangles.  In  performing  these  operations  practically,  the  student  may  be  assisted  by  the 
following  graphic  method  (used  by  Prof.  Cooke,  of  Harvard  University).  It  is  based  upon 
Napier's  rules,  which  are  familiar  to  every  student : 

In  a  right-angled  spherical  triangle  the  sine  of  any  part  is  equal  to  the  product  of  the 
cosines  of  the  opposite  parts,  or  the  proiuct  of  the  tangents  of  the  adjacent  parts.  Here  it 
is  to  be  remembered  that  for  the  two  angles  and  hypothenuse  the  complements  are  to  be 
taken. 

The  problems  are  represented  graphically  as  follows  :  In  the  case  given,  suppose  that  the 
basal  angle  (Z)  on  the  given  octahedron  has  been  measured  and  found  to  be  84°  19'  46",  that 
is,  the  angle  A  =  $Z  =  42°  9'  53",  and  hence  90"  —  A  =  47°  50'  7".  Then  the  parts  of  the 
triangle  may  be  written,  commencing  with  (7, 


b  (45 


903  (C) 
(90°  -  A) 


(90°  -  B) 


(90°  -  h). 


If  B  is  required,  we  have  (for  zircon)  sin  (90°  —  B)  =  cos  45°  x  cos  47°  50'  7" ; 
whence  B  =  61°  39'  47", 

and  the  vertical  angle  (X)  is  123°  19'  34". 

Also,  sin  45°  =  tan  a  x  tan  47°  50'  7", 

tan  a  =  0.640373  =  <-,  the  vertical  axis. 


62  CRYSTALLOGRAPHY. 

For  convenience,  some  of  the  more  important  formulas  for   the  solution   of  spherical 
triangles  are  here  added. 

In  spherical  right  triangles  C  =  90°. 

sin  a  sin  b 


tan  b  tan  a 

Cos  A  =  -  —  -  cos  B  —  -  --  j- 

tan  h  tan  h 

tan  a  tan  b 

Tan  A  =  —  tan  B  =  - 

sin  b  sin  a 

cos  B  cos  A 

Sin  A  =  —  sin  B  =  — 

cos  b  cos  a 

cos  k  =  cos  #  cos  & 
cos  A  =  cot  A  cot  .5 


In  oblique-angled  spherical  triangles  : 

(1)  Sin  A  :  sin  .Z?  =  sin  a  :  sin  5  ; 

(2)  Cos  a  =  cos  b  cos  c  +  sin  b  sin  c  cos  A  ; 

(3)  Cot  5  sin  c  =  cos  c  cos  A  +  sin  ^4  cot  B\ 

(4)  Cos  J.  =  —  cos  B  cos  C  +  sin  J?  sin  C  cos  a. 

-.  •.  • 

In  calculation  it  is  often  more  convenient  to  use,  instead  of  the  latter  formulas,  those 
especially  arranged  for  logarithms,  which  will  be  found  in  any  of  the  many  books  devoted 

to  mathematical  formulas. 

i 

Cosine  formula.  —  General  equation  for  the  inclination  of  two  planes  in 
the  orthometric  systems. 

Representing  the  parameters  of  any  plane  by  c  :  b  :  a,  and  also  of  any 
other  plane  by  c'  :  V  :  a',  and  placing  W  for  the  supplement  of  their 
mutual  inclination, 

p     -TTT_  aa'bb'+cc'aaf 

~~ 


a'*V*  +  c"W  +  5'V2) 

In  using  this  equation,  the  actual  values  of  the  parameters  are  to  be  sub- 
stituted for  the  letters.  For  the  planes  m-n,  in'-n'  ',  in  the  same  octant,  in 
which  the  parameters  would  be  me  :  nb  :  a,  and  m'c  :  n'~b  :  a, 

me,  nb,  a  are  substituted  severally  for  c,  5,  a. 
m'c,  n'b,  a  "  "          "  cf,  b',  a'. 


I.  ISOMETRIC  SYSTEM. 

The  equality  of  the  axes  in  the  Isometric  system  makes  it  unnecessary  to 
consider  them  in  the  calculations.  The  most  commonly  occurring  prob- 
lems are  the  determination  of  the  symbols  in  the  various  forms,  i-n,  m, 
m-m,  m-n  (f.  51,  54,  65,  69).  These  cases  will  be  considered  in  succession. 
In  all  but  the  last,  but  a  single  measurement  is  necessary. 

1.  Form  i-n,  tetrahexahedron. — The  edges  are  of  two  kinds  (p.  18),  as 
A  and  C  in  f.  244 ;  a  measurement  of  either  is  sufficient  to  determine  the 
value  of  n.  (a)  Given  the  angle  of  the  edge  A.  Suppose  a  plane  to 


MATHEMATICAL    CRYSTALLOGRAPHY. 


63 


pass  through  the  edge  A  and  the  adjoining  axis,  ac,  also  a  second  plane 
through  the  two  lateral  axes,  and  imagine  a  spherical  triangle  con- 
structed, as  explained  on  p.  61. 
This  triangle  (see  f.  244A)  is  right 
angled  at  C,  and  the  other  angles 
are  -faA,  (half  the  measured  angle  of 
the  crystal)  and  45°,  respectively. 
Hence,  if  v  is  the  inclination  .of  the 
plane  on  the  lateral  axis,  aff, 

cos  v  =  cos  \A  1/2, 

and  tan  v  =  na  =  n. 

(b)  Suppose  the  angle  of  the  edge  C 

to  be  given.     In  the  plane  triangle 

(abc)  of  the  section  in  f.  244,  \C  + 

45°  +  v  =  180°,  or   v  =  135°-  J<7, 

and,  as  before,  tan  v  =  n.     If  the  angle  of  two  opposite  planes,  meeting  at 

the  extremity  of  an  axis,  were  given,  half  this  angle  would  be  the  angle  v. 

For  a  series  of  tetrahexahedrons  the  tangent  law  may  be  applied,  since 

they  form  a  zone  between  two  cubic  planes;  the  dodecahedron  falls  in  this 

zone,  being  a  special  case  of  the  tetrahexahedron  where  n  =  1.     The  angle 

between  a  plane  i-n  and  the  adjoining  cubic  face  (H~)  is  equal  to  v  +  90°, 

hence,  cot  H=n. 

2.  Form  m,  trigonal  trisoctahedron. — The  edges  are  of  two  kinds,  A 
and  B.  (a)  If  the  angle  over  B  is  given,  suppose  a  diagonal  plane  to 
pass  through  the  vertical  axis  and  the  edge  A, 
meeting  the  planes,  as  indicated  in  the  figure. 
A  right-angled  plane  triangle  is  formed,  of  which 
the  basal  angle  is  equal  to  -JJ?,  and  the  base  is 
the  diagonal  line  x.  Then  x  tan  ^Bj=  the 
vertical  side  of  the  triangle  (m#),but  x  —  V-J-  when 
a  =  1,  whence  tan  $jBV$  —  ma  or  m,.  (b)  If 
the  given  angle  is  that  of  the  edge  A,  place 
a  spherical  triangle  (ma),  as  indicated  in  the 
figure.  In  this  triangle  C '=  90°  (for  the  diagonal 
plane  is  perpendicular  to  the  plane  m),  and  the 
other  angles  are  respectively  %A  (half  the  mea- 
sured angle)  and  60° ;  hence,  the  side  opposite 
\A  (=  the  angle  p)  is  obtained.  Further,  the 
angle  of  the  two  dotted  diagonals  (the  octahe- 
dral and  dodecahedral  axes)  is  35°  16'  (p.  16), 
whence,  \B  =  144°  44'  —  p,  and,  as  before, 
tan  \B^-\  —  m.  See  further  the  following  case.  The  general  equations 
are  thus : 

(a)  tan 


cos  p  =  2  cos 


=  144°  44'-p. 


3.  Form  ra-ra,  tetragonal  trisoctahedron. — Suppose  (a)  that  the  angle  of 
the  edge  B  is  given.     In  the  spherical  triangle  1,  in  f.  246,  C  —  90°,  and 


64 


CRYSTALLOGRAPHY. 


each  of  the  other  angles  equals  -| 
(=  angle   v)   is   obtained,   and    tan 


246 


B.  Hence,  one  of  the  equal  sides 
v  —  m.  (b)  If  the  angle  C  is  given, 
the  triangle  2,  in  f. 246, is  employed; 
=  90°,  a  second 


angle 


s 


here  one 

=  60°,  and  the  third  =  i<7,  half 
the  measured  angle  of  the  edge  C. 
The  side  of  the  triangle  —  the  angle 
p  is  calculated,  and,  as  in  the  preced- 
ing case,  f  =  144°  44'—  p,  then  7/14-  1 
=  tan  f  V%. 

The  planes  m-m,  1,  m,  form  a 
zone  between  the  cubic  and  dodeca- 
hedral  planes  as  f.  461,  p.  244,  to 
which  the  tangent  law  may  be  often 
conveniently  applied.  The  form  in 
passes  into  the  octahedron  1  when 
m  —  1,  and  when  m  is  less  than 
unity  it  becomes  m-m,  as  explained 
on  p.  17. 

Since  these  planes  form  a  rectangular  zone  the  tangent  of  the  supple- 
ment angles  between  them  and  a  cubic  plane  are  proportional  to  the  values 
of  m  for  the  given  forms  ;  only  by  applying  this  principle  for  m-ni,  the 

index   —  (=  —  :!:!)   will    be    obtained,   which  is   equivalent   to   m-m 
m        m 

(=  1  :  m  :  m). 

The  general  equations  for  the  form  m-m  are  : 


cos  v  =  cot  \B  ;  tan  v  —  m. 


cos  p  =  cot  \C 


=  144°  44'  - 


tan 


=  m  +  1. 


4.  Form  m-n,  hexoctahedron.  —  The  edges  of 
the  hexoctahedron  are  of  three  kinds,  A,  B,  C 
(f.  247),  and  two  measurements  are,  in  general, 
needed  in  order  to  deduce  the  values  of  m 
and  n. 

(a)  Given  A  and  13.  In  the  oblique-angled 
spherical  triangle  I  (f.  247),  the  three  angles 
are  \A,  \B,  and  45°.  In  this  triangle,  the 
side  opposite  \A  (=.  angle  v)  is  calculated,  and 
from  it  are  obtained  the  values  of  m  and  n, 
as  follows  : 


_cos£J.v/2  +  cos  \B 


sin 


tan 


sin  v  =  m  ;  tan  v  —  n. 


(b)  Given  A  and  C.  In  the  oblique-angled  triangle  II  (f.  247),  the  three 
angles  are  equal  respectively  to  -JJ.,  \C,  and  60°  The  side  opposite  \A 
(=  angle  p)  is  calculated.  But  the  angle  between  the  diagonals,  that  is, 
the  octahedral  and  dodecahedral  axes,  is  35°  16',  and  the  third  angle  of 
the  triangle  is  f,  the  inclination  of  the  edge  C  on  the  dodecahedral  axis  ; 


MATHEMATICAL    CKYSTALLOGKAPHY. 


65 


hence,  I  =  144°  44'—  p.  Again,  in  the  right-angled  triangle  III  (f.  247),  one 
angle  =^C\  and  the  adjacent  side  —  p,  whence  the  other  side,  8  (the  in- 
clination of  the  edge  B  on  the  dodecahedral  axis),  is  obtained  ;  v  =135°—  S, 
and  from  this,  as  above,  and  from  the  angle  p,  are  deduced  the  values  of 
m  and  n.  The  formulas  are  : 


cos  p  — 


2  cos 


sin 


V3 


4Ao  AA'  * 

—  ;  f  —  144°  44  —p  ;  tan  8  =  sin  f  tan  \C. 


v  =  135°—  8 ;  tan  v  =  n  ; 


n 


tan     =  m. 


(c)  Given  B  and  C.  In  the  right-angled  triangle,  III  (f.  247),  the  two 
angles  are  given,  equal  respectively  to  ^B  and  \C.  From  the  triangle  is 
deduced  the  side  opposite  -J-  (7  (=  angle  8  defined  before),  and  from  it  is 
obtained  v,  and  from  v  and  ^B,  the  values  of  m  and  n,  as  in  the  first  case. 
The  formulas  are  : 


cos  8  =  -,  —  ?-=  ;  v  =  135°—  8  ;  tan  v  =  n\  tan 


sn 


sn  v  =  m. 


If,  instead  of  m-n,  the  form  is  m -,  only  one  measurement  is  needed, 

and  the  process  is  simplified. 

When  the  angles  of  any  plane  m-n  on  two  cubic  planes  are  given,  their 
supplements  will  be  the  angles  of  the  plane  upon  the  corresponding 
diametral  sections,  and  from  them  the  values  of  m-n  may  be  readily  calcu- 
lated. Thus  (in  f .  248),  the  angles  of  a  given  plane  on  a  cubic  plane  at 
a?  will  be  the  supplement  of  its  angle  upon  the 
section  cr?as,  that  is,  the  angle  B  in  the  spherical 
triangle ;  similarly,  the  angle  of  a  cubic  plane  at 
as  will  be  the  supplement  of  its  angle  on  the 
section  ala\  the  angle  A  in  the  spherical  triangle. 
In  this  same  triangle  C  =  90°.  Hence,  the  sides 
opposite  A  and  B,  that  is,  the  inclinations  of  the 
two  edges  on  the  adjacent  axis,  may  be  calculated, 
and  this  axis  being  equal  to  unity,  their  tangents 
will  give  the  corresponding  lengths  of  the  other 
axes.  These  lengths  may  not  be  the  values  of  m 
and  n  in  the  form  in  which  the  symbol  is  generally 
written,  where  the  unit  axis  is  always  the  shortest, 
but  the  latter  are  immediately  deducible.  For  ex- 
ample, if  the  angles  here  mentioned  for  the  plane  numbered  4  (in  f.  247)  had 
been  measured,  the  values  of  the  axes  obtained  by  calculation,  when  the 
front  axis  is  the  unit,  would  be  -J  and  i  respectively,  and  the  symbol,  hence, 
•J-  :  -J-  :  1,  which  is  equivalent  to  1 :  f  :  3,  or  m-n  =  3-f  for  the  general  form. 

Hemihedral  forms. — For  each  hemihedral  form  the  formulas  are  iden- 
tical with  those  already  given  for  the  corresponding  holohedral,  so  far  as 
the  edges  of  the  two  are  the  same.  For  example,  in  comparing  f.  69  and 
f.  87  it  is  seen  that  the  edges  A  and  C  are  the  same  in  both,  while  B  of 
the  holohedral  form  differs  from  B'  of  the  hemihedral.  The  formulas  re- 
5 


66  CRYSTALLOGRAPHY. 

quired  to  cover  these  additional  cases  are  given  below,  they  are  obtained 
in  a  manner  similar  to  those  in  the  preceding  pages. 

Form  -J(m),  f.  85.     Given  B  '. 

cos  e  =  2  cos  %B'V\  ;  ?  =  35°  16'+  e  ;  tan 
Form  -J(m-m),  f.  81.     Given  B'. 

tan  %B'V%  =  m. 
Form  %(m-n\  f.  87.     (a)  Given  A'  and  B  '. 

COB 


0 
cos  a  —  —  —  \--r-i  ;    cos  p'=  -  —  =-^7  :  m  =  —  ——Q  ;  n  —  — 

sm  \A  '  sin  \B  '  cot  a—  cot  /3  '  cot  a  +  cot  £. 

5      Given  ^'  and  (7'. 


2  COS  \B'  +  COS  ot^o  ^r>/  i   ?>  i  >o»     • 

cos  e  =  -  _  —  ;  f  =  35°  16  +  e  :  cot  8  =  tan  \C'  sm  f. 

sin 


tan  (S  +  450)  rz:  n\       -     tan  f  =  7/i. 

7Z/  "i   J. 

Form  J[i-w],  f.  92.     Given  A". 

tan  %A"=  n. 
Form  [w-ra],  f.  100.     (a)     Given  A"  and  jS7/. 

cos  %A"  n  cos  4^4 

.    •  ,  y^  =  cos  y  :  tan  i/  =  n  :  -     —  1-±»" 
sin  4^"  cos  J.B 


(J)     Given  A"  and  C" 

*sy,+  /T  Q      cos  OVs  —  cos  \A" 

2  cos  J^  \\  —  sm  (9:  cos  0  = — =-= . 

siiiiA^v  2 

tan  (45°  +  6)  =  m  ;  sin  (45°  +  0)  tan  JJ."=  7*. 
(o)     Given  j3/r  and  67r/. 


cos  ~  cos 

2  cos 


Bm 
tan  (45°+  S)  =  n;  sin  (45°  +  6)  tan  \B"  =  m. 

The  various  combinations  of  hol<  hedral  and  hemihedral  forms  which 
may  occur  are  unlimited,  and  it  would  be  unwise  to  attempt  here  to  show 


MATHEMATICAL    CRYSTALLOGRAPHY. 


67 


the  methods  of  working  them  out.  It  is  only  necessary  to  remark  that  the 
solution  can  generally  be  readily  obtained  by  the  use  of  one  or  two  spheri- 
cal triangles  in  the  way  shown  in  the  preceding  cases. 

The  calculation  of  the  interf acial  angles  between  two  known  forms  can 
often  be  performed  by  the  formulas  already  given,  or  by  similar  methods. 
For  the  more  general  cases,  reference  must  be  made  to  the  cosine  formula, 
p.  62. 

Interf  acial  Angles. — I.  Holohedral  Forms. 

The  following  are  some  of  the  angles  among  the  more  common  of 
Isometric  holohedral  forms;  adjacent  planes  are  to  be  understood,  unless 
it  is  stated  otherwise.  The  angles  A,  B,  C\  above,  are  those  over  the 
edges  so  lettered  in  the  figures  referred  to  (see  pp.  15-19),  or  over  the 
corresponding  edges  in  related  forms : 


//A   #=90°,  f.  38  1  A 
//A   1  =125  16',  f.  40,  41         1  A 

H  A    *  =  135,  f.  43,  45.  1  A 

H  A  *-f  =  U6  19  lA 

//  A  i-2  =  153  26,  f .  64  1  A 

//  A  £-3  =  161  34  1  A 

//A  14  =  133  19  IA 

j^A  14  =  136  45  1  A 

H  A  2-2  =  144  44,  f.  55  fc  A 

H  A  3-3  =  154  46  *  A 

//At,  ov.  1,=  115  14  *  A 
HA  2,     "     =  109  28,  f .  52        i  A 

#A3,     "     =10316  *A 

H  A  3-|  =  143  18,  f.  70  %  A 

H  A  4-2  =  150  48  i  A 

H  A  5-|  =  147  41  *A 

1  A  i  =  109  28,  f.  42  i  A 

1  A  1,  top,=  70  32  *  A 

1  A  *  =  144  44,  f .  47  2-2  A 

1  A  i-\  =  143  11  2-2  A 

1  A  *-2  =  140  16,  f.  67  2-2  A 

1  A  *-3  =  136  54  3-3  A 

1  A  l-l  =  168  41  3-3  A 


2-2  =  160°  32',  f.  58 
3-3  =  150  30,  f.  57 

1  =  169  49 

2  =  164  12,  f.  53 

3  =  158 

3-|  =  157  45 

4-2  =  151  52 

54  =  151  25 

i  =  120  f.  45 

£,  ov.  top,  =  90 

*-f  =  167  42 

i-2  =  161  34,  f.  68 

f-3  =  153  26 

2-2  =  150 

3-|  =  160  54 

3-3  =  148  31 

44  =  166  6 

54  =  162  58| 

2-2,  £,=  131  49,  f.  54 

2-2,  (7,  =  146  27 

2-2,  ov.  top.  =109  28 

3-3,  £,=  144  54,  f.  61 

3-3,  (7,  =  129  31 


a-f  A  z'-l,  4  =  133°  49' 
H  A*-f,  6',  =  157  23 
i-2  A  i-2,  A,  =  143  8,  f.  65 
i-2  A  *-2,  (7,  =  143  8 
i-2  A  *-2,  ov.  top,  =  126  52 
i-2  A  *-3  =  171  52 
i-2  A  2-2  =  155  54 
j-3  A  *-3,  A.=  154  9,  f.  66 
i-3  A  *-3,  CL=  126  52 
2  A  2,  .4,  =  152  44,  f.  51 

2  A  2,  £,=  141  3! 

3  A  3,  A,=  142  8 

3  A3,£,=  153  28! 
3-|,  A,  =  158  13,  f,  69 
3-|,  £,=  149 
34,  GY,=  158  13 
4-2,  A,=  162  15 
4-2,  £,=  154  47! 
4-2,  C,  =  144  3 
54,  A,  =  152  20 
54,  £,=  160  32 
54,  C,  =  152  20 


II.  Hemihedral  Forms. 
The  following  are  the  angles  for  the  corresponding  hemihedral  forms : 

1  A  1  =  70°  32',  f.  76,  76A  3-3  A  3-3,  €',=  134°  2' 

x  |  A  f,  A,=  162  39!      3-|  A  3-|,  A,=  158  13,  f.  87 
|  A  I,  £,=  8210        3-|  A  3-|,  £,=  110  55! 

2  A  2,  A<=  152  44,  f.  85   3-*  A  3-|,  £',=  158  13 

2  A  2,  £,=  90          4-2  A  4-2,  A,=  162  15 

3  A  3,  A,  =  142  8        4-2  A  4-2,  £,=  124  51 
3  A  3,  £,=  99  5         4-2  A  4-2,  C,=  144  3 

|-|  A  H,  £,=  93  22  a-f  A  H,  A,=  112  37 

H  A  H,  C,=  160  15  i-l  A  *'-!,  G*  =  117  29 

2-2  A  2-2,  £,=  109  28,  f.  81  i-2  A  i-2,  4,=  126  52,  f.  92,  93 

2-2  A  2-2,  C,=  146  26!  i-2  A  *-2,  6*,=  113  35 

3-3  A  3-3,  £,=  124  7  £-3  A  «-3,  4,=  143  8 

In  the  forms  *"-},  *-2  (f .  92),  ^-3,  ^-4,  ^1  is  the  angle  at  the  longer  edge, 
and  C  that  at  either  of  the  others. 


^-3  A  ^-3,  (7,=  107 3  27|' 
4-2  A  4-2,  .4,  =  128  15 
4-2  A  4-2,  £,=  154  47! 
4-2  A  4-2,  G>,=  131  49 
3-|  A  3-|,  A,  =  115  23,  f.  100 
3-|  A  3-|,  £,=  149 
3-|  A  3-|,  C',=  141  47 
5-f  A  54,  A,=  119  3! 
5-f  A  54,  £,=  160  33 
54  A  54,  C,  =  131  5 


68  CRYSTALLOGRAPHY. 


II. — TETRAGONAL  SYSTEM. 

In  the  Tetragonal  system,  as  has  been  fully  explained  (p.  30),  the  length  of 
the  vertical  axis  is  variable,  and  must  be  determined  for  each  species.  If  the 
length  of  c  is  known,  then  it  may  be  required  to  determine  the  symbols  of 
certain  planes  by  means  of  measured  angles.  These  two  problems  are  in  a 
measure  complementary  to  each  other,  and  the  same  methods  will  give  a 
solution  to  either  case.  (For  figures  of  the  forms  see  pages  27  and  28.) 
The  calculation  of  the '  interracial  angles  can  be  performed  by  similar 
methods  or  by  the  cosine  formula. 

1.  Form  m. — The  edges  are  of  two  kinds,  pyramidal  X,  and  basal  Z. 
If  either  angle  is  known,  the  angle  a,  which  is  the  inclination  of  the  edge 
X  on   the  lateral  axis,  may  be  calculated  by  the  spherical  triangle,  as  in 
f.  242,  243.     (Compare  the  explanation  of  this  case,  p.  62.)     Obviously  in 
the  plane  right-angled  triangle  formed  by  the  two  axes  and   the  edge  X, 
tan  a  =  me  (since  a  =  1).     If  cis  known,  then  in  is  determined  ;   and,  con- 
versely, a  value  being  assumed  for  m,  in  the  special  case,  c  is  given  by  the 
calculation.     The  general  formulas  are  : 

cot  ^X=  sin  a,  or  tan  \Z  V  -J-  =  tan  a ;  then  tan  a  =  me. 

2.  Form  m-i. — (a)  Given  the  angle  Z,  me  is  found  immediately  ;  the 

solution  is  obvious,  for  in  the  section  indicated  by 
the  dotted  line  (f .  249),  \Z  =  a,  and  the  tangent  of 
this  angle  is  equal  to  the  vertical  axis,  (b)  Given 
the  angle  Y.  A  spherical  triangle  placed  as  in 
f.  249,  has  one  angle  =  -J-  Y,  a  second  =  45°,  and 
the  third  =90°,  whence  the  side  opposite  -J-F is 
calculated,  which  is  the  complement  of  a. 

The  general  formulas,  which  may  serve  to  de- 
duce the  value  of  my  when  c  is  given,  or  the  con- 
verse, are : 

cos  -J-  Y 1/2*  =  sin  a,  or  tan  \Z  =  tan  a,  and  tan  a  =  me. 

If  a  series  of  square  octahedrons  m,  or  m-i,  occur  in  a  vertical  zone,  their 
symbols  may  be  calculated  in  both  cases  alike  by  the  law  of  the  tangents, 
the  angles  of  the  planes  on  O,  or  on  /,  or  i-i,  respectively,  being  given. 
(See  p.  60.) 

3.  Form  i-n. — For  the  angle  of  the  edge  X(f.  109,  p.  26),  at  the  extrem- 
ity of  a  lateral  axis,  tan  %X  —  n.     From  the  angle  of  the  other  edge  Y9 
we  have  iX  =  135°-  £F;   an.d  hence,  tan  (135°--  J-F)  =  n. 

4.  Form  m-n. — The  edges  are  of  three  kinds,  X,  Y,  Z(L  250),  and  two 
angles  must  be  given  in  the  general  case  to  determine  m  and  n. 

(a)  Given  Xand  Z.  A  spherical  triangle  having  its  vertices  on  the  edges 
Xand  Z,  and  the  lateral  axis,  as  1,  f.  250,  will  have  two  of  its  angles  equal 
to  ^X,  $Z,  respectively,  and  the  third  equal  to  90°.  The  solution  of  this 
triangle  gives  the  sides,  viz.,  a  and  v,  the  inclinations  of  the  edges  X  and 


MATHEMATICAL    CRYSTALLOGRAPHY. 


69 


Z,  respectively,  on  the  lateral  axis.     The  tangents  of  these  angles  give  the 
values  of  m  and  n.     The  formulas  are  as  follows  : 


=  cos  a,  tan  a  =  me  ; 


COS 


sm 


=  cos  v.  tan  v  =  n. 


250 


(b)  Given  Y  and  ^.     In  a  second  triangle  placed  as  indicated  (2,  f  .  250), 
two  of  the  angles  are  -J]Tand  \Z  respectively, 
and  the  third  is  90°.     The  solution  of  this  second 
triangle  gives  8,  the  inclination   of   the  edge  Z 
on  the  diagonal  axis,  from  which,  in  the  plane 
triangle  we  have  v  —  135°  —  S,  and  from  v  is  ob- 
tained n.    Still  again  from  the  triangle  1  (f.  250), 
and  its  solution  used  in  the  preceding  case,  having 
given    Z  and  v,  a   is  obtained,  and  from  it  m  ; 
as  by  the  following  formulas  : 


=  cos  8,  v  —  135°— 8,  tan  v  =  n  • 

tan  \Z  sin  v  —  tan  a  —  me. 


cos 
sin 


(c)  Given  ^and  Y.  A  third  triangle,  numbered  3  in  the  figure,  has  two 
of  the  angles  equal  toJ-JTand  -J-  Irrespectively,  and  the  third  is  45°.  Solv- 
ing this  oblique-angled  triangle,  the  angle  of  the  inclination  of  the  edge  Y 
on  the  vertical  axis  is  obtained,  and  its  complement  is  the  angle  e,  the  in- 
clination of  the  edge  Y  oi\  the  diagonal  axis;  from  e  and  -J  Y  are  obtained, 
by  triangle  2,  S,  and  thence,  as  above,  n\  and  finally,  from  X  and  v,  is 
obtained'a,  and  from  that  the  value  of  m.  The  simplified  formulas  are  as 
follows  : 


cos 


cos 


=  n—\  ;  sin  a—  n  cot  \X,  tan  a  —  me. 


Pyramids  of  the  general  symbol  I-TI,  m-m,  etc.,  are  especial  cases  of  the 
preceding,  the  processes  being  for  them,  however,  somewhat  simplified.  A 
single  measurement  is  sufficient. 


III.  HEXAGONAL   SYSTEM. 

In  the  Hexagonal  system  tjiere  are  three  equal  lateral  axes  (a)  inter- 
secting at  angles  of  60°,  and  a  fourth  vertical  axis  (c)  at  right  angles  to 
the  plane  of  the  others.  Taking  a  =  1,  there  remains  but  one  unknown 
quantity  in  the  elements  of  a  crystal,  that  is  the  length  of  c,  and  a 
single  measurement  is  sufficient  to  determine  this.  The  relations  of  tin* 
three  lateral  axes  have  been  explained  on  p.  32. 

The  hexagonal  system  is  closely  allied  to  the  tetragonal,  and  optically 
they  are  identical,  as  is  shown  beyond. 

Schrauf  refers  all  hexagonal  forms  to  two  lateral  axes  crossing  at  right 


70  CRYSTALLOGRAPHY. 

angles  and  a,vertical  axis,  in  order  to  show  this  relation.  According  to  him.,  in 
this  system,  the  axes  are  c  :  aV3  :  a  ;  in  the  tetragonal  they  are  c  :  a  :  a. 
Miller's  school,  on  the  contrary,  employ  three  equal  axes,  making  equal 
angles  with  each  other,  and  each  normal  to  a  face  of  the  fundamental  rhom- 
bohedron.  In  each  of  these  methods  a  holohedral  form,  for  instance  a 
hexagonal  pyramid,  is  considered  as  made  up  of  two  sets  of  forms,  having 
different  indices. 


A. — Holohedral  Forms. 

1.  Form  m :  hexagonal  pyramid,  first  series. — Suppose  a  spherical  trian- 
gle, inscribed  in  f .  148,  p.  33,  having  its  vertices  upon  the  edges  X  and  Z, 
and  the  corresponding  lateral  axis  respectively,  similar  to  the  triangle  of 
f .  242.     This  will  be  a  right-angled  triangle. 

(a)  When  the  angle  of  the  edge  X  is  given,  then  f,  the  inclination  of  the 
edge  X  upon  the  adjoining  lateral  axis,  is  calculated  : 

sin  f  =  cot  \ X  1/3,  and  tan  f  —  me,  or  =  c,  the  vertical  axis,  when  m  =  1. 

(b)  Given  the  angle  Z. 

tan  •§•  Z  \/£  =  me,  or  =  c  when  m  —  1. 

2.  Form  m-2  :  hexagonal  pyramid,  second  series. — These  pyramids  bear 
the  same  relation  to  those  of  the  m  series  as  the  m-i  octahedrons  to  m  octa- 
hedrons of  the  tetragonal  system.     (Compare  f.  112,146.)     The  methods  of 
calculation  are  similar  (f.  249.)     The  edges  are  of  two  kinds,  vertical  .Fand 
basal  Z. 

(a)  Given  the  angle  Y. 

2  cos  \  Y  =  sin  JZ,  and  tan  \Z  —  me,  or  c  when  m  —  1. 

(b)  Given  the  angle  Z.     Then  simply 

tan  \Z  =  me. 

3.  Form  i-n:  dihexagonal  prism. — The  vertical  edges  are  of  two  kinds, 
axial  X,  and  diagonal  &\  the  solution  in  either  case  is  by  means  of  a  plane 
triangle,  in  a  cross-section  analogous  to  that  of  f.  146. 

(a)  Given  X. 

tan 

(b)  Given  Y. 


MATHEMATICAL    CRYSTALLOGRAPHY. 


71 


4.  Form  rn-n :  dihexagonal  pyramid. — The   edges  (f.  251)   are  of  three 
kinds,  X  and  Y  terminal,  and  Z  basal ;  measurements  of 
two  of  these  are  required  to  give  the  values  of  m  and 
n  ;  this  is  analogous  to  the  calculation  for  the  form  m-n 
in  the  preceding  system. 

(a)  Given  JTand  Z.  In  a  spherical  triangle  having  its 
vertices  on  the  edges  X  and  Z,  and  the  adjoining  lat- 
eral axis  respectively,  two  angles  are  given.  If  v  —  the 
inclination  of  the  edge  Z  upon  the  lateral  axis  (the  side 
of  the  spherical  triangle  opposite  the  angle  \X.  ),  then 


cos  v  — 


cos 


sn 


n 


—  i  =  tan  (v  -  30°)  Vj- ;  tan  \Z  sin  v  = 


mo. 


(b)  Given  T  and  Z.  The  right-angled  spherical  triangle  has  its  vertices 
on  the  edges  Y  and  Z  and  the  diagonal  axis.  If  B  =  the  inclination  of 
the  edge  Z  upon  this  diagonal  lateral  axis,  then  : 


cos  B  = 


cos 


Sill 


;  but  n  -  i  =  tan  (120°-  8) 


also 


(150°—  5)  =  v  ;  and,  as  before,  tan  -JZ"  sin  v  =  mo. 


(c)  Given  Xand  Y.  In  the  oblique-angled  spherical  triangle,  with  its 
vertices  upon  the  edges  X  and  Y  and  the  vertical  axis,  the  three  angles 
are  known,  viz.,  JJT",  -Jl7,  and  30°,  hence  : 


2-n 

71-  1 


cos 


cos  -J-l7" 


Further,  if  f  =  the  angle  of  inclination  of  the  edge  X  upon  a  lateral 
axis,  that  is,  the  complement  of  the  same  edge  upon  the  vertical  axis  (the 
side  of  the  "spherical  triangle  opposite  the  angle 

sin  £  =  n  — — .  cot 
2  —  n 


,  and  tan  f  —  me. 


If  the  pyramid  m-n  takes  the  form  m- ,  as  determined  bv  its  zonal 

m—l 

relations,   the  calculations  are    simplified,    since  one  unknown   quantity 
only,  m,  has  to  be  determined,  and  one  measurement  is  sufficient. 


B. — Rhombohedral  Division. 

The  relation  of  the  rhombohedrons  and  scalenohedrons  to  the  true  hexa- 
gonal forms  has  been  made  clear  in  another  place.  The  rhombohedron  is 
the  hemihedral  form  of  the  hexagonal  pyramid  m,  and  its  symbol  is  writ- 


72 


CRYSTALLOGRAPHY. 


ten   ^  ,  or  usually  mR.     The  scalenohedron  is  the  corresponding  hemihe- 

2i 

dral  form  of  the  twelve-sided  pyramid,  and  its  symbol  is  written  $(m-ri)  or 
m'Rn'.  The  latter  symbol,  proposed  by  Naumann,  has  reference  to  the 
rhombohedron  whose  lateral  edge  corresponds  to  the  edge  X  of  the  given 
scalenohedron. 

The  formulas  given  by  Naumann  for  reducing  the  symbol  \(rn-ri)  to  the 
form  m'Rnf  are  as  follows  : 


n 


,  and  nf  =  — 


n 


For  the  converse,  to  reduce  m'Rnr  to  the  form 


m  =  m'n'  and  n  = 


n'  +  1 


1.  Rhombohedrons^  mR. — The  methods  of  calculation  are  simple,  and 
will  be  understood  from  f.  252.  The  edges  are  of 
two  kinds,  X  and  Z,  and  their  relation  is  such  that 
the  corresponding  angles  are  the  supplements  of 
each  other. 

Given  the  angle  of  the  edge  X.  A  spherical 
triangle  is  placed,  as  indicated  by  AHC\iu  f.  252, 
with  its  vertices  respectively  on  the  edge  JT,  the 
vertical  axis,  and  the  diagonal  of  the  rhoinbohe- 
dral  face.  In  this  triangle  A  =  \X,  B  =  60°, 

I    /-y          nAO     r.  COS  A.  COS  -^>X 

and  6  =  90  ,  but  cos  a   =    = — ; 

sin  B  sin  60°' 

here  a  is  the   inclination   of   the  diagonal   line 
upon  the  vertical  axis,  that  is,  the  complement  of 
a,  its  inclination  upon  the  basal  section.     Now  iri  the  plane  triangle  abc, 
where  ac  =  the  lateral  axis  =  1,  ab  =  V$,  hence,  tan  a  V%  =  me,  or  =  c, 
the  vertical  axis  of  the  rhombohedron,  when  m  —  1. 
The  general  formulas  are  then  : 


cos 


sin  a  =   — — ^7T5  ,  and  tan  a  4/£  =  me. 


Obviously,  when  the  angle  of  R  (or  mR)  upon  the  basal  plane  O  can  be 
measured,  the  supplement  of  this  is  the  angle  a.     Similarly  the  angle  R  A 1 

—  JO      :=:   Cd.  •_ 

In  a  series  of  rhombohedrons  in  a  vertical  zone,  the  tangent  law  can  be 
advantageously  applied.  Attention  must  also  be  called  to  the  zonal  relations 
of  certain  -f-  and  —  rhombohedrons,  remarked  on  p.  36  ;  these  relations 
may  be  conveniently  shown  by  means  of  Quenstedt's  method  of  projection. 
^  2.  Scalenohedrons,  mRn. — As  seen  in  f.  171,  p.  37,  the  edges  are  of  three 
kinds,  X,  Y,  Z,  and  two  angles,  must  in  general  be  measured  to  allow  of 


MATHEMATICAL   CRYSTALLOGRAPHY.  73 

the  determination  of  m  and  n.     The  methods  of  calculation  are  not  alto- 
gether simple.     The  following  equations  are  from  Naumann. 

(a)  Given  Xand  Y. 

r 
also, 


n  is  found  from  *L±1  =  ^!*4  5    f  urther>  sin  *Z  =  — 1 cos 

71  —   1  COS-J]T  71-   +    -1 


,  '\'7 

cos  f7  —  -  — 7=^)  and  cot  f  '/S  =  me. 


Given  X  and  Z. 


sin^-Z  tan^Z  ,  /- 

==  -  T-^  ;  cos  £'=  -  7=—  ;  cot  £  r  3  = 
cos-JJT 


(c)  Given  l^and  Z. 

2n  sin^-Z  tan  -JZ  /- 

S^T1=  ^TT  ^      cos  r  :      -^T?  and  cot  fV  3  -  me. 

If  m,  that  is  the  inscribed  rhombohedron,  is  known,  one  measurement 
will  give  the  value  of  n.  Z'  =  basal  edge  of  the  inscribed  rhombohedron 
(care  must  be  taken  to  note  whether  0  is  obtuse  or  acute). 

(d)  Given  X  sin  0  =  2  cos  %X  cos  \Z  '. 

tan  ((/>-!£')  cotiZ'  =  n. 

(e)  Given  J".  sin  <£  =  2  cos  ^Fcos  4Z'. 

tan 
(/)  Given  Z.  tan  ^Z,  cot  \Zr  =  n. 

If  n  is  known.     From  X,  we  have  sin  -JZ  —  —  —  cos  \X  ;    then,   as 


under  (a).     From  Y,  sin  ^Z  =  —  !L  cos  ^-J",  and  then  as  above.     From  Z, 

n—l 
cos  f  '  is  obtained  as  under  (a),  and  then  mo. 


TV.  ORTHORHOMBIC  SYSTEM. 

Of  the  three  rectangular  axes  in  the  Orthorhombic  system,  one  is  always 
taken  equal  to  unity,  in  this  work  the  shortest  (a).  This  leaves  two 
unknown  quantities  to  be  determined  for  each  species,  namely,  the  lengths 


74 


CRYSTALLOGRAPHY. 


of  the  axes  c  and  5,  expressed  in  terms  of  the  unit  axis  #,  and  for  this 
end  two  independent  measurements  are  required.  The  simpler  cases  are 
considered  here. 

Calculation  of  the  Lengths  of  the  Axes. 

Let    a  =  the  inclination  of  the  edge  Z  to  the  axis  a  (f .  253). 
$  =  the  inclination  of  the  edge  X  to  the  axis  a. 
7  =  the  inclination  of  the  edge  T^to  the  axis  b. 

From  the  plane  triangle  formed  by  each  edge  and  the  axes  adjacent 
(f.  253,  254)  the  following  relations  are  deduced,  when  a  =  1  : 

1)  Given  a  and  /?,      tan  fB  =  c  and  _tan  a  =  T). 

2)  Given  a  and  7,      tan  a  =  £,  and  b  tari  7  —  4 

3)  Given  (3  and  7,      tan  ft  =  c,  and  c  cot  7  =  b. 


253 


254 


The  angles  a,  /?,  7  are  often  given  direct  by  measurement ;  for,  obviously 
(f.  254,  255), 

a  =  the  semi-prismatic  angle  /A /(over  i-l). 

ft  =  the  semi-basal  angle  of  14  A  14. 

7  =  the  semi-basal  angle  of  14  A  1-L 

Also  /A  *4  =  a  +  90°  ;  14  A  i-l  =  ft  +  90°  ;  U  A  0  =  180°-y3,  etc. 

From  the  octahedron  (f.  253),  the  angles  a,  /3,  7  are  calculated  immedi- 
ately by  the  following  formulas,  and  from  them  the  length  of  the  axes  as 
above. 

(a)  Given  X  and  Z  (spherical  triangle  I,  f.  253), 


cos  a  = 


cos 


;.cos      = 


cos 


sin  i>Z,  sin 

(b)  Given  F  and  Z  (spherical  triangle  II,  f.  253), 


cos-  £  x  cos 

sm  a  =  „  ;  cos  7  = 

sin  ^Z  sin 


(c)  Given  X  and  P"  (spherical  triangle  III,  f .  253), 


MATHEMATICAL    CKYSTALLOGEATHY.  75 

If  any  one  of  the  angles  a,  0,  or  7  is  given,  as  from  the  measurement  of 
a  prism  or  dome,  and  also  any  one  of  the  angles  of  the  octahedral  edges  X, 
X,  or  Z,  a  second  of  the  former  angles  may  be  calculated,  and  from  the 
two  the  axes  are  obtained  as  before.  The  formulas,  derived  from  the 
same  spherical  triangles,  are  as  follows  : 

(1)  Given  X  and  a,         sin  ft  —  cot  \X  tan  a. 

X  and  ft,         tan  a  =  tan  \X  sin  ft. 
X  and  7,         cos  ft  =  cot  \X  cot  7. 

(2)  Given   JTand  a,         sin  7  —  cot  Jl^cot  a. 

J^  and  /3,         cos  y  =  cot^Y  cot  £. 
.Fand  7,         cot  a  =  tan  -Jl7  sin  7. 

(3)  Given    Z  and  a,         tan  7  =  tan  \  Z  cos  a. 

Z  and  /?,         cos  a  =  cot  ^  Z"  tan  7. 
Z  and  7,         sin  a  =  cot  %  Z  tan/3. 


Calculation  of  the  values  of  m  and  n. 

The  above  formulas  cover  all  the  ordinary  cases,  the  only  change  that  is 
required  in  them  is  to  write  for  c,  b,  a,  in  equations  (1),  (2),  (3),  above,  c',  b',  af, 
the  lengths  of  the  axes  for  the  given  form,  noting  that  c'  —  me,  and  so  on. 

1.  Prisms,  i-n  or  i-n.     As  remarked,  the  semi-prismatic  angle  (over  i-l) 
is  the  angle  a  (f.  254),  and   tan  a  —  nb.     If  the  calculated  value  of   n  is 
greater  than  unity,  the  form  is  written  oo  c  :  nb  :  a  (i-n) ;  if  less  than  unity, 
the  form  is  written  oo  c  :  b  :  na  (i-n),   b  being   the   unit    axis.     Thus  i-J 
(oo  c  :  \1)  :  a)  becomes  i-$  (oo  c  :  b  :  2a). 

2.  Domes,  m-i  and  m-L — No  farther  explanation  is  needed  (f .  255) ;  here 
tan  ft  =  me,  or  b  tan  7  =  me. 

3.  Octahedrons,  m. — Here  the  angle  a   is  always  known  (it  being  the 
same  as  for  the  unit-octahedron  where  tan  a  =  b),  and  hence  a  single  meas- 
ured angle, -X,  Y,  or  Z  will  give  the  values  of  either  ft  or  7  for  the  given 
form,  and  tan  ft  =  me,  b  tan  7  —  mo. 

4.  Forms  m-n  or  m-fi. — The  measurement  of  the  angles  X,  Y,  Z  will 
give  the  values  of  a,  ft,  and  7  belonging  to  the  given  form,  and  tan  ft  =  me, 
tan  a  =  nb,  etc. 

Here,  as  in  the  prisms,  if  n  is  less  than  unity,  when  the  axis  d  is  the  unit, 
the  symbol  is  transposed,  and  the  axis  b  made  the  unit,  thus  2c :  %b  :  a  (2- J) 
becomes  4#  :  b  :  2a  (4-2). 

If  the  angle  between  the  form  m-n  (or  m-n)  and  either  of  the  pinacoids 
can  be  measured,  the  method  of  calculation  is  essentially  the  same  (Com- 
pare f .  248)  ;  for 

m-n  A  O  (base)  =  supplement  of  the  angle  \Z\ 

m-n  A  i-i  (macropinacoid)  =  supplement  of  the  angle  -J-  Y ;  and 

m-n  A  i-l  (brachypinacoid)  —  supplement  of  the  angle  \X. 

The  method  of  calculation  of  planes  in  a  rectangular  zone  by  means  of 
the  tangents  of  their  supplement  basal  angles  finds  a  wide  application  in 
this  system.  It  applies  not  only  to  the  main  zones  0  to  i-l  (macrodoines), 


76 


CRYSTALLOGKArHY. 


O  to  i-l  (brachy  domes),  i-l  to  i-l  (vertical  prisms),  and  /  to  0  (unit  octahe- 
drons), but  also  to  any  zone  of  octahedrons  m-n  (or  m-n)  between  O  and  i  n 
(or  i-n\  and  any  transverse  zone  from  i-l  to  ra-£,  and  i-l  to  m-l. 


V.  MONOCLINIO  SYSTEM. 

In  the  Monoclinic  system  the  number 
of  unknown  quantities  is  three,  viz.,  the 
lengths  of  the  axes  c<  and  &,  expressed  in 
terms  of  the  unit  clinodiagonal  axis  #,  and 
the  oblique  angle  ft  (also  called  O),  between 
the  basal  and  vertical  diametral  sections, 
that  is,  between  the  axes  c  and  d.  Three 
independent  measurements  are  needed  to 
determine  these  crystallographic  elements. 

The  angle  ft  is  obtuse  in  the  upper  front 
quadrants,  and  acute  in  the  lower  front 
quadrants;  the  planes  in  the  first  mentioned 
quadrants  are  distinguished  from  those  be- 
low by  the  minus  sign.  The  unit  octahe- 
dron is  made  up  of  two  herni-octahedrons 
(—1  and  +  1),  as  shown  in  f.  256. 

Calculation  of  the  Lengths  of  the  Axes, 
and  the  Angles  of  obliquity. 
Represent  (see  f.  256)  the  inclination  of  the 


Edge  X  on  the  axis  c  by 


X  on  d  by  v.     Y  on  c  by  p. 
X  on  d  by  v'.    Z  on  d  by  <r. 


For  the  relation  of  the  axes  in  terms  of  these  angles  we  have  : 
(1)  In  the  oblique-angled  plane  triangle,  in  the  clinodiagonal  section  : 

sin  v 


a  :  G  =  sm  LL  :  sm  v,  or,  c  = 


sin//, 


when  a  =  1. 


tan   i  = 


tan  v  = 


a  sin  ft 
c  —  a  cos  ft' 

G  sin  ft 
a  —  c  cos  /3' 


a  sin  ft 

tan  a  =  — • 5. 

c+a  cos  ft 


=    ^ 


sin    ju  — 


tan  v  = 
tan£  = 


<?  sin  ft 
a  +  G  cos/3 

2  sin  v  sin  v' 

sin  (v  —  v)  ' 


Further,  p  +  v  4-  ft  =  180°  ///  +  i/'=  £. 

(2)  In  the  right-angled  triangle  of  the  orthodiagonal  section,  b  cot  p  =  <?. 


MATHEMATICAL    CRYSTALLOGRAPHY.  77 

(3)  In  the  basal  section,  d  tan  a-  =  b. 

The  above  formulas  serve  to  determine  the  lengths  of  the  axes,  and  the 
angle  of  obliquity,  or,  if  these  are  known,  to  determine  the  values  of  in  and 
n  by  substituting  mo  for  c,  etc. 

the  angles  /^,  v,  p,  <r,  etc.,  must,  in  general,  be  determined  by  calculation 
from  measured  angles. 

Let  the  inclination  of  a  plane  in  the  positive  quadrant  on  the  clinodi- 
agonal  section  be  denoted  by  X\  that  on  the  orthodiagonal  section  by  Y\ 
that  on  the  basal  section  by  Z.  Let  also  the  corresponding  inclinations  of 
a  plane  in  the  negative  quadrants  be  indicated  by  X  ',  Y'  Z'  respectively 
(see  f.  256). 

It  is  to  be  noted,  when  the  pinacoids  are  present,  that 


+  1  A  O  =  180°-  Z;      +  lAa  =  180°-]T;     +  1  A*4  =  180°-X; 

F'     -  1  A  i-i  =  180°-X'. 


The  same  is  true  for  the  corresponding  angles  of   the  general  form 

m-n,  or  m-h. 

Also,  when  ±  1  (f.  256)  alone  are  present  (or  m-n)  note  that 

+  1  A  +  1  =  2X;  -  1  A  -  1  =  2JT  ;    +  1  A  -  1  (orthodiag.)=  T+  Yf  ; 

(basal)  = 


Any  three  of  these  angles  will  serve  to  give  for  the  unit  form  (±1)  the 
length  and  obliquity  of  the  axes,  or,  when  these  are  known,  two  of  these 
angles  are  sufficient  to  deduce  the  values  of  m  and  n  for  any  unknown 
form. 

In  the  first  case,  as  one  of  the  three  measured  angles  must  be  either 
Y-}-  Y'  or  Z  +  Z'  ,  the  formulas  given  above  do  not  immediately  apply. 

For  example,  if  JT,  X!  and  Y+  Y'  are  given.  Placing  a  spherical 
triangle,  abc,  in  f.  256,  with  its  vertices  on  the  edges  JJT,  X7,  and  Y, 
in  this  the  three  angles  will  equal  X,  X'  and  Y+  Y  respectively  ;  here 
the  side,  00,  opposite  the  angle  (Y+Y)  is  calculated,  which  gives  the  value 
of  //,  +  /*',  also  the  side,  bo,  opposite  X'  ;  then,  again,  in  the  right-angled 
spherical  triangle,  where  bo  and  X  are  known,  /u,  is  obtained,  thus  ///  is 
known  and  also  ft.  The  lengths  of  the  axes  follow  from  the  formulas 
given  above. 

The  following  are  some  of  the  cases  which  may  occur: 

(a)  Given  O,  and  i-i.     O  f\i-i  (front)  =  180°—  /3,  behind  =  /?. 

(b)  Given  0,  -  I-i,  and  +  I-i.    Oh—l-i=  180°—  v'  ;   O  A  +  I-i  =  180° 

—  v.     By   the  formula  given  above,  tan  fi  —  -j  —        —  7--,  also,  //,  =  180° 

—  (j3+v).     Thus  £,  yu,  and  i/  are  known,  and  from  them  the  relation  of  the 
axes  d  and  c  is  deduced. 


(c)  Given  ^',  —  l--i  and  +  I-i.  i-i  A  —  1-*  =  180°—  p',i-i  A  +  I-i  =  180 
-  ^    As  before,  tan  ft  =  2',  and  v  =  180°-  (/3  +  /.). 


CRYSTALLOGRAPHY. ' 


(d)  Given  the  prism  I  and  O  (f.  257).  In  the  spherical  triangle  ABC, 
C  =  90°  (inclination  of  base  on  cli  nodi  agon  al  section),  B  =  O  A  /,  A  = 
i(/A  I).  Hence,  the  sides  OA  and  CB  are  calculated  ;  CA  =  /3  (or,  as 

in  this  case,  180°—  /3) ;    CB  —  <7,  which  gives  the  ratio 

of  the  lateral  axes,  d  and  b. 


(e)  Given  14  and  O  (or  i-l).     O  M4  —  90°  +  p,  and 
i-l  A  14  =  180°—  p  ;  also,  14  A  14  (over  0)=  2p. 

(/)  Given  +  1  and  —  1,  form  as  in  f.  256.  The 
angles  between  the  planes  +  1  and  —  1  and  the  diame- 
tral sections  are  indicated  by  the  letters  X,  Y,  etc.,  as 
before  explained  (p.  77).  The  relations  between  these 
angles  and  the  angles  //,,  v,  p,  etc.,  are  given  in  the  fol- 
lowing formulas,  deduced  by  means  of  spherical  triangles : 


cos  Y 

cos  u,  —  — ^, 

sin  X' 


cos 


cos  Y 

—  -  =™  . 

sm  JT5 


COS  p  = 


cos 


X 


sin 


=^ 

Y 


cos  v  — 


cos  Z 


also, 


sm 


cos  v  — 


cos  Z' 


cos  X       cos  Xf 


-.7-     tan  <7       tan  p 

tan  X=  -: =  - — " 

sin  i/       sin  IL 


fim  T^_ 

tan  I  — 


tan  yu, 
sin  p 


,7, 
tan  Y= 


tan 


sin 


—  -  ==7,       COS    <7  =  —  r  -  T     =  —  -  7= 

sin  Xn  sm  Z        sm  Z' 


nrry tan  cr       tan  p 

tan  j\.  ^-  — ; .       — -. 

sm  v       sm  LU 


tan  p  tan  i/ 

tan  Z  =    .  — ,     tan  Z  =  — . 

sin  cr  sm  o- 


S  Given  the  prism  I  and  —  1  (or  +  1).  The  angles 
j  —  lA/,  —  lA—  1  are  measured.  In  the  spherical 
triangle  ABD  (f.  258),  the  angle  A  =  $(/A  /),  B  =  - 
1  A  /,  D  =  4(—  1  A  —1)  =  X,  "irom  which  the  sides  AD 
=  v'  +  (180°  -  /3)  and  AB  are  calculated.  Then  in  the 
second  triangle,  ABC,  C  —  90°,  AB  is  known,  also  A  ; 
i  ence,  (7j£  =  <rand  <7J[  =  180°  -  13  are  calculated.  Thus 
?/  and  /*'  and  /8  become  known,  and  the  relation  of  «  to 
^  :  also  from  <7  follows  the  ratio  of  d  to  b. 


Calculation  of  the  values  of  m  and  n. 

In  general,  it  may  be  said  that  the  methods  of  calculation  are  the  same 
as  those  already  given.  In  each  case  the  values  of  p,  v,  p,  cr  are  to  be 
obtained,  and  those  introduced  into  the  axial  equations  (1,  2,  3)  given 
above  give  the  values  of  me,  nb,  etc.,  from  which  m  and  n  are  derived. 
When  in  the  general  form  m-n  (me  :  nb  :  a)  n  is  found  to  be  less  than 
unity,  then  b  is  made  the  unit  axis  and  the  form  is  written  m-n  (me  : 
1}  :  no),  thus  2#  :  ^b  :  a  becomes  4c  :  b  :  2a  (4-S),  the  same  is  true  for  i-n 
and  \~n. 

1.  Hemi-octahedrons,   ±  m-n. — Two  measurements   are  needed,  giving 


MATHEMATICAL    CRYSTALLOGRAPHY.  79 

two  of  the  angles  X,  I7",  Z,  etc.,  from  which  are  derived  /*  (or  v\  p  (or  <r), 
and  from  the  proper  formulas  m  and  n. 

The  following  hemi-octahedrons  require  one  measurement  only  :  ±  m, 
i  m-m,  ±  m-m,  ±  1-^,  ±  1-A.  Further,  it  is  to  be  noted  in  regard  to 
them  that  the  forms  ±  m  have  the  same  ratio  of  the  lateral  axes  as  ±  1, 
that  is,  the  same  value  of  cr. 

Forms  ±  1-w,  and  ±  m-m,  have  the  same  ratio  of  the  axes  c  and  #  as  the 
unit  form  ±  1?  that  is,  the  same  values  of  /-t,  i/  (/A',  v'). 

Forms  ±  m-m,  ±  i-A,  have  the  same  ratio  of  the  axes  c  and  b  with 
±  1,  that  is,  the  same  value  of  p. 

2.  Form  i-n  (or  i-n).  —  If,  as  before,  X,  Y  represent  the  inclinations  of 
the  given  prism  on  the  clinodiagonal  and  orthodiagonal  sections  respect- 
ively, it  is  to  be  noted  that  : 

X  +  T  =  90°. 
Similarly  to  f.  257,  we  obtain,  in  general,  for  any  form,  i-n, 

sin  fi  tan  X         ,  £      .  ^  J  cot  X 

n  =  -  —  -j  -  ;  and  for  ^-n.  n  —  —  :  —  ^-  . 
b  sm/3 

Since  i-i  A  i-l  =  90°,  the  tangent  law  can  be  applied  in  this  zone  advan- 
tageously. If  X1,  Yl  are  the  corresponding  angles  for  the  unit  prism  /, 
then  for  i-n, 

tan  X       tan  Y1  ,    .       .  v  tan  X1     tan  Y 

n  —  -  -  ^-  =  --  =        and   tor  ^-n,  n  =  -  -  ^^-—  -  -  =^r. 
tanJT1      tan  Y9  tan  X       tan  Y1 

3.  Forms  ±  m-i,  hemi-orthodomes.  —  For  each  form  the  corresponding 
values  of  /t,  v  (fju\  v)  are  to  be  obtained  by  measurement  or  else  calculated, 
and  from  them  the  value  of  mo  obtained  from  the  formulas  (1),  mo  = 

sin  v 

—  —  ,  etc. 
sin  //, 

4.  Forms  m4,  clinodomes.  —  Similarly  as  with  the  prisms,  when  X  and 
Z  denote  the  angles  with  the  clinodiagonal  and  basal  sections, 


For  any  form  m-i, 


c  sin  / 
Or  by  the  tangent  law,  X1  being  the  corresponding  angle  for  14, 

tanX1 

m  —  r  —^-' 
tan  X 


80  CRYSTALLOGRAPHY. 


TRICLINIC  SYSTEM. 

The  triclinic  system  is  characterized  by  its  entire  want  of  symmetry. 
The  inclinations  of  all  the  diametral  planes,  and  hence,  the  inclination  of 
the  axes,  are  oblique  to  one  another.  There  are,  then,  five  unknown  quan- 
tities to  be  determined  in  each  case,  viz.,  the  three  angles  of  obliquity  of 
the  axes,  and  the  lengths  of  the  axes  1}  and  c,  a  being  made  =  1. 

The  axes  are  lettered  as  in  the  orthorhombic  system :  c  =  the  vertical 
axis,  &  =  the  macrodiagonal  axis,  and  a  =  the  brachydiagonal  axis. 

Let  (f.  259)  a  =  angle  between  the  axes  c  and  £; 
@  =  angle  between  the  axes  c  and  a ; 
y  =  angle  between  the  axes  b  and  a. 
Also,  let  A  =  angle  of  inclination  of  the  diame- 
tral planes  meeting  in  the  axes  a  ;   B  =  angle  of 
inclination  for  those  intersecting  in  the  axis.  #,   and 
C  =  the  angle  of  those  meeting  in  c. 

The  macrodiagonal  (m-n)  and  brachydiagonal 
(m-n)  planes  are  indicated  as  in  the  orthorhombic 
system,  also  the  planes  opposite  the  acute  angle 
(jo)  are  called  +,  and  those  opposite  the  corre- 
spending  obtuse  angle  —  ;  furthermore,  the  planes 
in  front,  to  the  right  (and  behind,  to  the  left)  are  distinguished  by  an  accent, 
as  m-nf. 

In  the  fundamental  octahedron  formed  by  four  sets  of  planes,  these  are, 
taken  in  the  usual  order  (f.  227),  —  I7,  —  1,  +1',  +  1,  and  below,  +  1', 
+  1, -!',-!. 

In  the  determination  of  any  individual  crystal  belonging  to  this  system, 
the  axial  directions  as  well  as  unit  values  have  to  be  assumed  arbitrarily ; 
in  many  cases  (e.g.,  axinite)  the  custom  of  different  authors  has  varied 
much.  Two  points  are  to  be  considered  in  making  the  choice  :  1,  the  cor- 
respondence in  form  with  related  species,  even  if  these  be  not  triclinic,  as, 
for  example,  in  the  feldspar  family  ;  and  2,  the  ease  of  calculation,  which 
is  much  facilitated  if,  of  the  planes  chosen  as  fundamental,  the  pinacoids 
are  all,  or  at  least  in  part,  present. 

In  general,  the  methods  of  calculation  are  not  simple.  Some  of  the 
most  important  relations  are  given  here  (from  Naumann).  In  actual 
practice,  problems  which  arise  may  be  solved  by  some  of  the  following 
formulas,  or  by  means  of  a  series  of  appropriate  spherical  triangles,  used 
as  in  the  preceding  pages,  and  by  which,  from  the  measured  angles,  the 
required  elements  of  the  forms  may  be  obtained. 

In  addition  to  the  angles  already  defined,  let,  as  follows  (f.  259), 

X—  inclination  of  a  plane  on  the  brachydiagonal  section  ; 
T  —  "  "  "      macrodiagonal         " 

£=.         «  «  «      basal  " 

Let  the  inclination  of  the  edge, 

JT  on  c  =  fj,y  Y  on  c  =  /o,  Z  on  a  —  <r, 

X  on  a  =  v,  Y  on  b  —  IT,  Z  on  b  =  T, 


MATHEMATICAL    CRYSTALLOGRAPHY.  81 

When  the  three  pinacoids  are  present,  the  angles  A.,  B,  C  are  given  by 
measurement.  These  angles  are  connected  with  the  axial  angles  by  the 
following  equations  : 

cos  A  +  cos  B  cos  C  0      cos  B  +  cos  C  cos  A 

cos  a  =  -  :  —  TJ  —  :  —  7=  -  :      cos  p  =  -  :  —  -^  —  :  —        —  ; 
sin  B  sm  C  sin  C  sin  A 

cos  C  +  cos  A  cos  B 
cos  7  =  -  r-    —  ;  —  jj-   —  : 
sin  A  sin  B 

also, 

sin  a  :  sin  /3  :  sin  y  =  sin  A  :  sin  B  :  sin  C. 

The  relations  between  the  angles  a,  /9,  %  and  the  angles  p,  v,  etc.,  are  as 
follows  : 

2  sin  p  sin  p'       2  sin  TT  sin  TT' 
tan  a  =  —.  —  f-  -  £•  =     .  —  7—     —-. 
sm  (p  —  p1)         sin  (TT  —  TT  ) 

~      2  sin  //,  sin  u!       2  sin  z>  sin  v' 
tan  £  =  -,  —  f-    —  £-  =  —  —  -  --  —  . 
sin  yc*  —  fi)         sin  (v  —  v) 

_  2  sin  r  sin  T'  __  2  sin  <r  sin  a-' 
sin  (r  —  T')    '       sin  (or  —  a)  ' 
Also, 

a  +  TT  +  p  —  j3  +  p  +  v  =  y  +  <r  +  T  =  180°. 

The  relations  between  X,  J".  Z,  and  J.,  ^,  (7,  and  //,,  z/,  etc.,  are  given 
by  the  following  formulas,  in  which  the  sum  and  difference  of  X  and  I7*, 
etc.,  are  calculated,  and  from  them  the  angles  JT,  Y,  etc.,  themselves  are 
obtained  : 


tan     X  +  F   =  cot 


COS  J(p  +  //,) 

tan  «X-  r)  -  cot   \0  .  *™  $>  ~  ^. 

sm  t(p  +  fi) 

cos      °"  ~  v 


if-r-      v\  ± 

tan  i(X+  Z)  =  cot 

i  /  TT       /7\  . 

tan  i(X—  Z)  =  cot 


.          ? 
cos  j(cr 

sin  -cr 


.    —  --  . 
sm  i(cr  +  i/) 

tan  i(  JT+  Z)  =  cot  \B  .  <**#?-•*) 

cos  i(r  +  TT) 

1  /  T7-  a  \  4    1    Z>       Sm   "2  (T  —   T) 

tan  %(Y—  Z)  =  cot  i^  .  -,  —  f)—    —  (. 

sm  -i(T  +  TT) 


82 


CRYSTALLOGRAPHY. 


COS  It  = 


COS   p  = 


COS  (7  = 


cos  Y  +  cos  Jfcos  C 

;  -  =F^=  —  -.  -  7==  -  , 

sin  Y  sin  (7 

cos  JT+  cos  I^cos  C 

-  :  -  =F-F  —  :  -  7?  -  , 

sin  Y  sin  Z 
cos  JJT  +  cos  Z  cos  ^1 

-  :  -  ~  —  :  -  1  -  . 

sm  Z  sin  A 


COS  V  = 


COS  7T  = 


COS   T  = 


cos  Z  +  cos  X  cos  A 

-  :  -  =^—.  -  2  -  . 

sin  X  sin  A 
cos  Z  +  cos  JTcos  B 

-  ;  -  „     . 

sin  ]T  sin  ft 
cos  1^+  cos  Z  cos  ./? 

-  :  -  ^  —  :  -  ^  -  . 

sin  Z  sin  1$ 


Further, 


sin  X  :  sin  ]F  =  sin  p 
" 


sn 
sin 


:  sin  Z  =  sin  T 
:  sin  JL  =  sin  v 


sm  /A. 

SHITT. 


sn  cr. 


The  following  equations  give  the  relations  of  the  angles  /JL,  v,  p,  etc.,  to 
the  axes  and  axial  angles  : 


tan  a  = 


a  sn 


- 

c  —  a  cos  ft 

1}  sin  a 

tan  p  =  -  7  -  : 
G  —  o  cos  a 


e  sin  ft 
tan  v  = 


tan  TT  = 


—  ^. 
a  —  G  GOB  ft 

c  sin  a 
y  —       -  . 
c>  —  c  cos  a 


£  sm  7 

y ,     tan  cr  = j — '- — . 

o  —  a  cos  7  a  —  o  cos  7 


&  sn  7 
tan  T  =  - 


Also, 

For  any  form  m-n, 


sn  T 
sin  p 
sin  i/ 


sn  o-  =  a  :    , 
sin  TT  =  #  :  c 


sn  JL  =  c  : 


^-i  =  180°— X\  m-n  A  0  =  180°  —  Z. 
For  a  vertical  hemiprism,  X+  T"+  6^=  180°, 

a  :  ^  =  sin  Y  .  sin  a  :  sin  X :  sin  ft. 
For  a  rnacrodiagonal  hemidome,  Y+Z  +  JB  =  180°, 
^  :  c  =  sin  T' .  sin  a  :  sin  Z .  sin  7. 
For  a  brachy diagonal  hemidome,  X+Z  +A  =  180°, 
?  :  c  =  sin  X  sin  /#  :  sin  Z  sin  7. 

By  writing  mo  for  c,  n5  for  5,  etc.,  these  formulas  will  answer  also  for 
the  determination  of  m  and  n.  It  is  supposed  in  the  above  that  the 
measured  edge  is  parallel  to  the  axis  of  the  given  hemiprism,  etc. ;  when 
this  is  not  the  case  the  relations  are  a  little  less  simple. 


MATHEMATICAL    CRYSTALLOGRAPHY. 


83 


MEASUREMENT  OF  THE  ANGLES  OF  CRYSTALS. 

The  angles  of  crystals  are  measured  by  means  of  instruments  which  are 
called  goniometers. 

The  simplest  form  of  these  instruments  is  the  hand-goniometer,  repre- 
sented in  f.  260.  It  consists  of  an  arc,  graduated  to  half  degrees,  or  finer, 


and  two  movable  arms.  In  the  instrument  figured,  one  of  the  arms,  #5, 
has  the  motion  forward  and  backward  by  means  of  slits  gh,  ik ;  the  other 
arm,  cd,  has  also  a  similar  slit,  and  in  addition  it  turns  around  the  centre  of 
the  arc  as  an  axis.  The  planes  whose  inclination  is  to  be  measured  are 
applied  between  the  arms  ao,  co9  and  the  latter  adjusted  so  that  they  and 
the  surfaces  of  the  planes  are  in  close  contact.  This  adjustment  must  be 
made  with  care,  and  when  the  instrument  is  held  up  to  the  light  none  must 
pass  through  between  the  arm  and  the  plane.  The  number  of  degrees  read 
off  on  the  arc  between  k  and  the  left  edge  of  d  (this  edge  being  in  the  line 
of  the  centre,  0,  of  the  arc)  is  the  angle  required.  The  motion  to  and  fro  by 
means  of  the  slits  is  for  the  sake  of  convenience  in  measuring  small  or 
imbedded  crystals.  In  a  much  better  form  of  the  instrument  the  arms  are 
wholly  separated  from  the  arc  ;  and  the  arc  is  a  delicately  graduated  circle 
to  which  the  arms  are  adjusted  after  the  measurement. 

The  hand-goniometer  is  useful  in  the  case  of  large  crystals,  and  those 
whose  faces  are  not  well  polished  ;  the  measurements  with  it,  however,  are 
seldom  within  a  quarter  of  a  degree  of  accuracy.  In  the  finest  specimens 
of  crystals,  where  the  planes  are  smooth  and  lustrous,  results  far  more 
accurate  may  be  obtained  by  means  of  a  different  instrument,  called  the 
reflecting  goniometer. 

Reflecting  Goniometer. — This  instrument  was  devised  by  Wollaston,  in 
1809,  but  it  has  been  much  improved  in  its  various  parts  since  his  time, 
especially  by  Mitscherlich.  The  principle  on  which  it  is  constructed  may 
be  understood  by  reference  to  the  following  figure  (f.  261),  which  repre- 
sents a  crystal,  whose  angle,  abc,  is  required. 

The  eye  at  P,  looking  at  the  face  of  the  crystal,  be,  observes  a  reflected 


84- 


CRYSTALLOGRAPHY. 


image  of  m,  in  the  direction  of  Pn.  The  crystal  may  now  be  so  changed  in 
its  position,  that  the  same  image  is  seen  reflected  by 
the  next  face  and  in  the  same  direction,  Pn.  To 
effect  this,  the  crystal  must  be  turned  around,  until 
p  abd  has  the  present  direction  of  bo.  The  angle  dbc, 
measures,  therefore,  the  number  of  degrees  through 
which  the  crystal  must  be  turned.  But  dbc,  subtracted 
from  1 80°,  equals  the  required  angle  of  the  crystal, 
abc.  The  crystal  is,  therefore,  passed  in  its  revolution 

through  an  angle  which  is  the  supplement  of  the  required  angle.     This 


angle  evidently  may  be  measured  by  attaching  the  crystal  to  a  graduated 
circle,  which  should  turn  with  the  crystal. 

The  accompanying  cut  (f.  262)  represents  a  reflecting  goniometer  made 


MATHEMATICAL    CRYSTALLOGRAPHY.  85 

by  Oertling,  in  Berlin.  It  will  suffice  to  make  clear  the  general  character 
of  the  instrument,  as  well  as  to  exhibit  some  of  the  refinements  added  for 
the  sake  of  greater  exactness. 

The  circle,  6y,  is  graduated,  in  this  case,  to  twenty  minutes,  and  by  means 
of  the  vernier  at  v  the  readings  may  be  made  to  minutes  and  half  min- 
utes. The  crystal  is  attached  by  means  of  wax  to  the  little  plate  at  k ; 
this  may  be  removed  for  convenience,  but  in  its  final  position  it  is,  as  here, 
at  the  extremity  of  the  axis  of  the  instrument.  This  axis  is  moved  by 
means  of  the  wheel,  n  ;  the  graduated  circle  is  moved  by  the  wheel,  m. 
These  motions  are  so  arranged  that  the  motion  of  n  is  independent,  its  axis 
being  within  the  other,  while  on  the  other  hand  the  revolution  of  m  moves 
both  the  circle  and  the  axis  to  which  the  crystal  is  attached.  This  ar- 
rangement is  essential  for  convenience  in  the  use  of  the  instrument,  as 
will  be  seen  in  the  course  of  the  following  explanation. 

The  screws,  c,  d,  are  for  the  adjustment  of  the  crystal,  and  the  slides, 
a,  £,  serve  to  centre  it. 

The  method  of  procedure  is  briefly  as  follows  :  The  crystal  is  attached 
by  means  of  suitable  wax  at  &,  and  adjusted  so  that  the  direction  of  the 
combination-edge  of  the  two  planes  to  be  measured  coincides  with  the  axis 
of  the  instrument ;  the  wheel,  n,  is  turned  until  an  object  (e.g.,  a  window- 
bar)  reflected  in  one  plane  is  seen  to  coincide  with  another  object  not 
reflected  (e.g.,  a  chalk  line  on  the  floor),  the  position  of  the  graduated  circle 
is  observed,  and  then  both  crystal  and  circle  revolved  together  by  means 
of  the  wheel,  m,  till  the  same  reflected  object  now  seen  in  the  second  plane 
again  coincides  with  the  fixed  object  (that  is,  the  chalk  line) ;  the  angle 
through  which  the  circle  has  been  moved,  as  read  off  by  means  of  the 
vernier,  is  the  supplement  angle  between  the  two  planes. 

In  order  to  secure  accuracy,  several  conditions  must  be  fulfilled,  of 
which  the  following  are  the  most  important : 

1.  The   position   of    the   eye   of  the  observer   must  remain  perfectly 
stationary. 

2.  The  object  reflected  and  that  with  which  it  is  brought  in  coincidence, 
should  be  at  an  equal  distance  from  the  instrument,  and    this  distance 
should  not  be  too  small. 

3.  The  crystal  must  be  accurately  adjusted ;  this  is  so  when  the  line 
seen  reflected  in  the  case  of  each  plane  and  that  seen  directly  with  which 
it  is  in  coincidence  are  horizontal  and  parallel.     It  can  be  true  only  when 
the  intersection  edge  of  the  two  planes  measured  is  exactly  in  the  direction 
of  the  axis  of  the  instrument,  and  perpendicular  to  the  plane  of  the  circle. 

4.  The  crystal  must  be  centered  as  nearly  as  possible,  or,  in  other  words, 
the  same  intersection -edge  must  coincide  with  a  line  drawn  through  the  re- 
volving axis.     This  condition  will  be  seen  to  be  distinct  from  the  preced- 
ing, which  required  only  that  the  two  directions  should  be  the  same.     The 
error  arising  when  this  condition  is  not  satisfied  diminishes  as  the  object 
reflected  is  removed  farther  from  the  instrument,  and  becomes  zero  if  the 
object  is  at  an  infinite  distance. 

The  first  and  second  conditions  are  both  satisfactorily  fulfilled  by 
the  use  of  a  telescope,  as  £,  f.  262,  with  slight  magnifying  power.  This 
is  arranged  for  parallel  light,  and  provided  with  spider  lines  in  its 
focus.  It  admits  also  of  some  adjustments,  as  seen  in  the  figure,  but 


86  CRYSTALLOGRAPHY. 

when  used  it  must  be  directed  exactly  toward  the  axis  of  the  goniometer. 
This  telescope  has  also  a  little  magnifying  glass  (g,  f.  262)  attached  to  it, 
which  allows  of  the  crystal  itself  being  seen  when  mounted  at  k.  This 
latter  is  used  for  the  first  adjustments  of  both  planes,  and  then  slipped 
aside,  when  some  distant  object  which  has  been  selected  must  be  seen 
in  the  field  of  the  telescope  as  reflected,  first  by  the  one  plane  and 
then  by  the  other  as  the  wheel  n  is  revolved.  When  the  final  adjustments 
have  been  made  so  that  in  each  case  the  object  coincides  with  the  centre  of 
the  spider-cross  of  the  telescope,  and  when  further  the  edge  to  be  measured 
has  been  centered,  the  crystal  is  ready  for  measurement. 

This  telescope,  obviously,  can  be  used  only  when  the  plane  is  smooth  and 
large,  enough  to  give  distinct  and  brilliant  reflections.  In  many  cases 
sufficient  accuracy  is  obtained  without  it  by  the  use  of  a  window-bar  and 
a  white  chalk  line  on  the  floor  below  for  the  two  objects  ;  the  instrument  in 
this  case  is  placed  at  the  opposite  end  of  the  room,  with  its  axis  parallel  to 
the  window  ;  the  eye  is  brought  very  close  to  the  crystal  and  held  motionless 
during  the  measurement. 

The  best  instruments  are  provided  with  two  telescopes.  The  second 
stands  opposite  the  telescope,  t  (see  figure),  the  centres  of  both  telescopes 
being  in  the  same  plane  perpendicular  to  the  axis  of  the  instrument. 
This  second  telescope  has  also  a  hair  cross  in  the  focus,  and  this,  when 
illuminated  by  a  brilliant  gas  burner  (the  rest  of  the  instrument  being 
protected  from  the  light  by  a  screen)  will  be  reflected  in  the  successive 
faces  of  the  crystal.  The  reflected  cross  is  brought  in  coincidence  with  the 
cross  in  the  first  telescope,  first  for  one  and  then  for  the  other  plane.  As 
the  lines  are  delicate,  and  as  exact  coincidence  can  take  place  only 
after  perfect  adjustment,  it  is  evident  that  a  high  degree  of  accuracy  is 
possible. 

Still  more  than  before,  however,  are  well-polished  crystals  required,  so 
that  in  the  majority  of  cases  the  use  of  the  ordinary  double  telescopes  is 
impossible.  Yery  often,  however,  the  second  telescope  may  be  advantage- 
ously replaced  by  another  having  an  adjustable  slit  in  its  focus,  as  proposed 
by  Websky,  allowing  of  being  made  as  narrow  as  is  convenient ;  or,  as  sug- 
gested by"  Schrauf,  the  spider-lines  of  the  second  telescope  may  be  re- 
placed by  a  piece  of  tin-foil,  in  which  two  fine  cross  lines  have  been  cut; 
these  are  illuminated  by  a  gas-burner.  By  these  methods  the  reflected 
object  is  a  bright  line  or  cross,  instead  of  the  dark  spider-lines,  and  it  is 
visible  in  the  first  telescope  even  when  the  planes  are  extremely  minute, 
or,  on  the  other  hand,  somewhat  rough  and  uneven  ;  the  image  is  naturally 
not  perfectly  distinct,  but  sufficiently  so  to  admit  of  good  measurements 
(e.g.^  within  two  or  three  minutes). 

The  third  and  fourth  conditions  are  the  most  difficult  to  fulfil  absolutely. 
In  the  cheaper  instruments  the  contrivance  to  accomplish  the  end  often 
consists  of  a  jointed  arm  so  placed  as  to  have  two  independent  motions  at 
right  angles  to  each  other.  In  the  best  instruments  the  greatest  care  and 
attention  is  paid  to  this  point,  and  a  great  variety  of  ingenious  contrivances 
have  been  devised  to  overcome  the  various  practical  difficulties  arising. 

The  cut  (f.  262)  shows  one  of  these  in  its  simpler  form.  The  crystal  is 
approximately  adjusted  by  the  hand,  and  then  the  operation  completed  by 
means  of  the  screws  c  and  d.  These  give  two  motions  at  right  angles  to 


MATHEMATICAL    CRYSTALLOGRAPHY.  87 

each  other,  and  the  arrangement  is  such  that  the  motions  are  made  on  the 
surface  of  a  spherical  segment  of  which  the  crystal  itself  occupies  the 
centre,  so  that  it  is  not  thrown  entirely  out  of  the  axis  of  the  instrument 
by  the  motions  of  the  screws.  The  adjustment  having  been  accurately 
made,  the  edge  is  centered  by  means  of  two  sliding  carriages,  a,  5,  moving 
at  right  angles  to  each  other ;  here  they  are  moved  by  hand,  but  in  better 
instruments  by  tine  screws.  The  edge  must  be  first  centered  as  carefully  as 
practicable,  then  the  complete  adjustments  made,  and  finally  again  centered, 
as  before,  to  remove  the  excentricity  caused  by  the  movement  of  the  ad- 
justment screws.  The  successful  use  of  the  most  elaborate  instruments  is 
only  to  be  attained  after  much  patient  practice. 

Theoretical  discussions  of  the  various  errors  arising  in  measurements  and 
the  weight  to  be  attached  to  them  have  been  given  by  Kuppfer  (Preis- 
schrift  liber  genaue  Messung  der  Winkel  an  Krystallen,  1825),  also  by 
Naumann,  Grailich,  Schrauf,  and  others  (see  literature,  p.  iv). 

It  has  been  stated  that  when  the  two  planes  have  been  adjusted  in  the 
goniometer  so  that  their  combination-edge  is  parallel  to  the  axis  of  the 
instrument,  the  reflections  given  by  them  will  be  parallel.  It  is  evident 
from  this  that  any  other  planes  on  the  crystal  which  are  in  the  same  zone 
with  the  two  mentioned  planes  will  also  give,  as  the  circle  is  revolved, 
reflections  parallel  to  these.  This  means  gives  the  test  referred  to  on 
p.  53,  leading  on  the  one  hand  to  the  discovery  of  zones  not  indicated  by 
parallel  intersections,  and  on  the  other  hand  showing,  in  regard  to  supposed 
zones,  whether  they  are  so  in  fact  or  not. 

The  degree  of  accuracy  and  constancy  in  the  angles  of  crystals  as  they  are  given  by  nature 
is  an  important  subject.  Crystallography  as  a  science  is  based  upon  the  assumption  that  the 
forms  made  by  nature  are  perfectly  accurate,  and  whenever  exact  measurements  are  possible, 
supposing  the  crystals  to  have  been  free  from  disturbing  influences,  it  has  been  found  that 
this  assumption  is  warranted  by  the  facts ;  in  other  words,  the  more  accurate  the  measure- 
ments the  more  closely  do  the  angles  obtained  agree  with  those  required  by  theory.  An 
example  may  illustrate  this  : — On  a  crystal  of  sphalerite  (zinc-blende),  from  the  Binnenthal, 
exact  measurements  were  made  by  Kokscbarow  to  test  the  point  in  question.  He  found  for 
the  angle  of  the  tetrahedron  70  J  31'  48",  required  70°  31'  44'  ;  for  the  octahedral  angle 
109°  27'  42",  required  109°  28'  16';  and  for  the  angle  between  the  tetrahedron  and  cube 
125°  15'  52 ',  required  125°  15'  52".  The  crystallographiu  works  of  the  same  author,  as  well 
as  those  of  many  other  workers  in  the  same  field,  contain  many  illustrations  on  the  same 
subject.  At  the  same  time  variations  in  angle  do  occasionally  occur,  from  a  change  in 
chemical  composition,  and  from  various  disturbing  causes,  such  as  heat  and  pressure  (see 
further,  p.  107).  Further  than  this,  it  is  universally  true  that  exact  measurements  are  in 
comparatively  few  cases  possible.  Many  crystals  are  large  and  rough,  and  admit  of  only 
approximate  results  with  the  hand  goniometer;  others  have  faces  which  are  more  or  less 
polished,  but  which  give  uncertain  reflections.  This  is  due  in  some  cases  to  striations,  in 
others  to  the  fact  that  the  surfaces  are  curved  or  more  or  less  covered  with  markings  or 
etchings,  like  those  common  on  the  pyramidal  planes  of  quartz.  In  all  such  cases  there  is  a 
greater  or  less  discrepancy  between  the  measured  and  calculated  angles. 

The  important  point  to  be  noted  always  is  the  degree  of  accuracy  attainably  or,  in  other 
words,  the  probable  error.  The  true  result  to  be  accepted  is  always  to  be  obtained  by  the 
discussion  of  all  the  measurements  in  accordance  with  the  methods  of  least  squares.  This 
method  involves  considerable  labor,  and  in  most  cases  it  is  sufficient  to  take  the  arithmetical 
mean,  noting  what  degree  of  weight  is  to  be  attached  to  each  measurement.  It  is  to  be  noted 
that  where  measurements  vary  largely  the  probable  error  in  the  mean  accepted  will  be  con- 
siderable ;  moreover  an  approximate  measurement  may  not  be  the  more  accurate  because  it 
happens  to  agree  closely  with  the  theoretical  angle. 

For  the  determination  of  the  symbols  of  planes,  measurement  accurate  within  30',  or  even 
1°,  are  generally  sufficient. 

When  planes  are  rough  and  destitute  of  lustre  the  angles  can  best  be  obtained  with  the 


88 


C  RYSTALLOGKAPH  Y. 


reflecting  goniometer,  the  reflections  of  the  light  from  an  object  like  a  candle-flame,  being 
taken  in  place  of  more  distinct  images. 

For  imbedded  crystals,  and  often  in  other  cases,  measurements  may  be  very  advantage- 
ously made  from  impressions  in  some  material,  like  sealing-wax.  Angles  thus  obtained  ought 
to  be  accurate  within  one  degree,  and  suffice  for  many  purposes.  It  is  sometimes  of  advan- 
tage to  attach  to  the  planes  to  be  measured,  when  quite  rough,  fragments  of  thin  glass,  from 
which  reflections  can  be  obtained ;  this  must,  however,  be  done  with  care,  to  avoid  consider- 
able error. 

COMPOUND,   OR   TWIN   CRYSTALS. 

TWIN  CRYSTALS  are  those  in  which  one  or  more  parts  regularly  arrranged 
are  in  reverse  position  with  reference  to  the  other  part  or  parts.  They 
often  appear  externally  to  consist  of  two  or  more  crystals  symmetrically 
united,  and  sometimes  have  the  form  of  a  cross  or  star.  They  also  exhibit 
the  composition  in  the  reversed  arrangement  of  part  of  the  planes,  in  the 
strise  of  the  surface,  and  in  re-entering  angles  ;  in  other  cases  the  compound 
structure  is  detected  only  by  polarized  light.  The  following  figures  are 
examples  of  the  simpler  kinds.  Fig.  263  is  a  twinned  octahedron  with 

264 


Spinel. 


Cassiterite. 


re-entering  angles.  Fig.  263A  represents  the  regular  octahedron  divided 
into  two  halves  by  a  plane  parallel  to  an  octahedral  face  ;  the  revolving  of 
the  upper  half  around  180°  produces  the  twinned  form.  Fig.  264  consists 
of  a  square  prism,  with  pyramidal  terminations,  twinned  parallel  to  a 
diagonal  plane  between  opposite  solid  angles,  as  illustrated  in  f.  264A, 
a  representation  of  the  simple  form.  A  revolution  of  one  of  the  two 
halves  of  f.  264A  180°  about  an  axis  at  right  angles  to  the  diagonal  plane 
outlined  in  the  figure,  would  produce  the  form  in  fig.  264. 

Crystals  which  occupy  parallel  positions  with  reference  to  each  other, 
that  is,  those  whose  similar  axes  and  planes  are  parallel,  are  not  properly 
called  twins  ;  the  term  is  applied  only  where  the  crystals  are  united  in  their 
reversed  position  in  accordance  with  some  deducible  mathematical  law.  In 
conceiving  of  them  we  imagine  first  the  two  individuals  or  portions  of  the 
same  individual  to  be  in  a  parallel  position,  and  then  a  revolution  of  180° 
to  take  place  about  a  certain  line,  as  axis,  which  will  bring  them  into  the 
twinning  position. 

An  exception  to  the  principle  in  regard  to  parallel  axes  is  afforded  in  the  case  of  hemihe- 
dral  crystals,  in  some  of  which  a  revolution  of  180°  has  the  effect  of  producing  an  apparently 
holohedral  form,  the  axes  of  the  parts  revolved  remaining  parallel. 


TWIN    CRYSTALS. 


89 


In  some  cases  (e.g,.  hexagonal  forms),  a  revolution  of  60°  would  produce  the  twinned 
form,  but  in  treating-  of  the  subject  it  is  better  to  make  the  uniform  assumption  of  a  revolu- 
tion of  ISO0,  which  will  answer  in  all  cases. 

It  is  not  to  be  supposed  that  twins  have  actually  been  formed  by  such  a  revolution  of  the 
parts  of  crystals,  for  the  twin  is  the  result  of  regular  molecular  growth  or  enlargement,  like 
that  of  the  simple  crystal.  This  reference  to  a  revolution,  and  an  axis  of  revolution,  is  only 
a  convenient  means  of  describing  the  forms.  But  while  this  is  true,  it  is  important  to  ob- 
serve that  the  laws  deduced  to  explain  the  twinning  of  a  crystal  have,  from  a  molecular 
standpoint,  a  real  existence.  The  measurements  of  Schrauf  on  twins  of  cerussite  (Tsch. 
Min.  Mitth.,  1873,  209)  show  the  complete  correspondence  between  the  actual  angles  and 
those  required  in  accordance  with  the  law  of  twinning. 

Twinning  axis. — The  line  or  axis  about  which  the  revolution  of  180°  is 
supposed  to  take  place  is  called  the  twinning-axis  (Zwillingsaxe,  Germ.\ 
or  axis  of  revolution. 

The  following  law  has  been  deduced  in  regard  to  this  axis,  upon  which 
the  theory  of  the  whole  subject  depends  : 

The  twinning  axis  is  always  a  possible  crystallographic  line,  usually 
either  an  axis  or  a  normal  to  some  possible  crystalline  plane. 

Twinning-plane. — The  plane  normal  to  the  axis  of  revolution  is  called 
the  twinnirig-plane  (Zwillingsflache,  Germ.).  The  axis  and  plane  of  twin- 
ning bear  the  same  relation  to  both  individuals  in  their  reversed  position  ; 
consequently  (except  in  some  of  hemihedral  and  tri clinic  forms)  the  twin- 
ned crystals  are  symmetrical  with  reference  to  the  twinning-plane. 

Composition-plane. — The  plane  by  which  the  reversed  crystals  is  united 
is  the  composition-plane  or  -face  (Zusammensetzungsflache,  Germ.).  This 
and  the  twinning-plane  very  commonly  coincide ;  tin's  is  true  of  the  simple 
examples  given  above  (f.  283,  264:)  where  the  plane  about  which  the  revolu- 
tion is  conceived  as  having  taken  place  (normal  to  the  twinning  axis),  and 
the  plane  by  which  the  semi-individuals  are  united,  are  identical.  When 
not  coinciding  the  two  planes  are  generally  at  right  angles  to  each  other, 
that  is,  the  composition  face  is  parallel  to  the  axis  of  revolution.  Examples 
of  this  are  given  beyond  (p.  99).  Still  again,  where  the  crystals  are  not 
regularly  developed,  and  where  they  interpenetrate,  and,  as  it  were,  exer- 
cise a  disturbing  influence  upon  each  other,  the  contact  surface  may  be 
interrupted,  or  may  be  exceedingly  irregular.  In  such  cases  the  axis  and 
plane  of  twinning  have,  as  always,  a  definite  position,  but  the  composition- 
face  has  lost  its  significance. 

Thus  in  quartz  the  interpenetrating  parts  have 
often  no  rectilinear  boundary,  but  mingle  in  the  most 
irregular  manner  throughout  the  mass,  and  showing 
this  composite  irregularity  by  abrupt  variations  of  the 
planes  at  the  surface.  Fig.  265  exhibits  by  its  shaded 
part  the  parts  of  the  plane  —  1  that  appear  over  the 
surface  of  the  plane  It,  owing  to  the  interior  composi- 
tion. This  internal  structure  of  quartz,  found  in  almost 
all  quartz  crystals,  even  the  common  kinds,  is  well 
brought  out  by  means  of  polarized  light ;  also,  by 
etching  with  hydrofluoric  acid,  the  plane  —  1  and  R 
becoming  etched  unequally  on  the  same  amount  of 
exposure  to  the  acid. 

The  twinning-plane  is,  with  rare  exceptions,  a  pos- 
sible occurring  plane  on  the  given  species,  and  usually  one  of  the  more 


90  CRYSTALLOGRAPHY. 

frequent  or  fundamental  planes.  The  exceptions  occur  only  in  the  triclinic 
and  monoclimc  systems,  where  the  twinning  axis  is  sometimes  one  of  the 
oblique  crystallographic  axes,  and  then  the  plane  of  twinning  normal  to  it 
is  obviously  not  necessarily  a  crystallographic  plane,  this  is  conspicuous  in 
albite.  In  these  cases  the  composition-face  is  often  of  more  significance 
than  the  twiiming-plane,  the  former  being  distinct  and  parallel  to  the 
axis,  in  accordance  with  the  principle  stated  above. 

With  reference  to  the  composition-face,  the  twinning  may  be  described  as  taking  place  (1) 
by  a  revolution  on  an  axis  at  right  angles  to  the  composition-face,  (2)  on  an  axis  parallel 
to  it  and  vertical,  (3)  by  an  axis  parallel  to  it  and  horizontal ;  whether  the  revolution 
takes  place  with  the  right  or  left  half  of  the  crystal,  the  twin  is  right-  or  left-handed. 

One  .further  principle  is  of  theoretical  importance  in  the  mathematical 
explanation  of  the  forms.  The  twinning  axis  may,  in  many  cases,  be  ex- 
changed for  another  line  at  right  angles  with  it,  a  revolution  about  which 
will  also  satisfy  the  conditions  of  producing  the  required  form.  An  exam- 
ple of  this  is  furnished  by  f.  318,  of  orthoclase  ;  the  composition-face  is 
parallel  to  i-\  the  axis  of  revolution  also  parallel  to  this  plane,  and  (a)  nor- 
mal to  iri,  which  is  then  consequently  the  twinning-plane,  though  the  axis 
does  not  coincide  with  the  crystallographic  axis,  or  (b)  it  may  coincide  with 
the  vertical  axis,  and  then  the  twinning-plane  normal  to  it  is  not  a  crys- 
tallographic plane.  In  other  simpler  cases  also,  the  same  principle  holds 
good,  generally  in  consequence  of  the  possible  mutual  interchange  of  the 
planes  of  twinning  and  composition.  In  most  cases  the  true  twinning-plane 
is  evident,  since  it  is  parallel  to  some  plane  on  the  crystal  of  simple  mathe- 
matical ratio. 

An  interesting  example  of  the  above  principle  is  furnished  by  the  species  staurolite. 
Fig.  307,  p.  98,  shows  a  prismatic  twin  observed  by  the  author  among  crystals  from  Fannin 
Co.,  Ga.  The  measured  angle  for  i-i  A  i-%  was  70°  30'  ;  the  twinning-axis  deduced  from 
this  may  be  the  normal  to  the  plane  £-f,  which  would  then  be  the  twinning-plane.  Instead 
of  this  axis,  its  complementary  axis  at  right  angles  to  it  may  be  taken,  which  will  equally 
well  produce  the  observed  form.  Now  in  this  species  it  happens  that  the  planes  £-3  and  i-\ 
(over  i-l)  are  almost  exactly  at  right  angles  (90°  8')  with  each  other,  and  hence,  according  to 
this  latter  supposition,  £-3  becomes  the  twinn  ng-plane,  and  the  axis  of  revolution  is  normal 
to  it.  Hence,  either  £-]J  or  «-§  may  be  the  twinning-plane,  either  supposition  agrees  closely 
with  the  measured  angle,  which  could  not  be  obtained  with  great  accuracy.  The  former 
method  of  twinning  (i-$)  conforms  to  the  other  twins  observed  on  the  species,  and  hence  it 
may  be  accepted.  What  is  true  in  this  case,  however,  is  not  always  true,  for  it  will  seldom 
happen  that  of  the  two  complementary  axes  each  is  so  nearly  normal  to  a  plane  of  the  crystal. 
In  most  cases  one  of  the  two  axes  conforms  to  the  law  in  being  a  normal  to  a  possible  plane, 
and  the  other  does  not,  and  hence  there  is  no  doubt  as  to  which  is  the  true  twinning  axis. 

Contact-twins  and  Penetration-twins. — In  contact-twins,  when  normally 
formed,  the  two  halves  are  simply  connate,  being  united  to  each  other  by 
the  composition-face ;  this  is  illustrated  by  f.  263,  264.  In  actually  occur- 
ring crystals  the  two  parts  are  seldom  symmetrical,  as  demanded  by  theory, 
but  one  may  preponderate  to  a  greater  or  less  extent  over  the  other ;  in 
some  cases  only  a  small  portion  of  the  second  individual  in  the  reversed 
position  may  exist.  Yery  great  irregularities  are  observed  in  nature  in  this 
respect.  Moreover,  the  re-entering  angles  are  often  obliterated  by  the  ab- 
normal developments  of  one  or  other  of  the  parts,  and  often  only  an  indis- 


TWIN    CRYSTALS. 


91 


266 


Fluorite. 


Hematite. 


tinct  line   on  some   of   the  faces   marks   the   division  between  the   two 
individuals. 

Penetration-twin*  are  those  in  which  two  or  more  complete  crystals 
interpenetrate,  as  it  were  crossing  through  each  other.  Normally,  the 
crystals  have  a  common  centre,  which  is  the  centre  of  the  axial  system  for 
both ;  practically,  however,  as  in  contact-twins,  great  irregularities  occur. 

Examples  of  these  twins  are 
given  ill  the  annexed  figures, 
f.  266,  of  fluorite,  and  f.  267,  of 
hematite.  Other  examples  occur 
in  the  pages  following,  as,  for 
instance,  of  the  species  staurolite, 
f .  309  to  312,  the  crystals  of  which 
sometimes  occur  in  nature  with 
almost  the  perfect  symmetry  de- 
manded by  theory.  It  is  obvi- 
ous that  the  distinction  between 
contact  and  penetration-twins  is 
not  a  very  important  one,  and  the  line  cannot  always  be  clearly  drawn 
between  them. 

Paragenic  and  Metagenic  twins. — The  distinction  of  paragenic  and 
metagenic  twins  belongs  rather  to  crystallogeny  than  crystallography.  Yet 
the  forms  are  often  so  obviously  distinct  that  a  brief  notice  of  the  dis- 
tinction is  important. 

In  ordinary  twins,  the  compound  structure  had  its  beginning  in  a  nncleal 
compound  molecule,  or  was  compound  in  its  very  origin  ;  and  whatever 
inequalities  in  the  result,  these  are  only  irregularities  in  the  development 
from  such  a  nucleus.  But  in  others,  the  crystal  was  at  first  simple  ;  and 
afterwards,  through  some  change  in  itself  or  in  the  condition  of  the  mate- 
rial supplied  for  its  increase,  received  new  layers,  or  a  continuation,  in  a 
reversed  position.  This  mode  of  twinning  is  metagenic,  or  a  result  subse- 
quent to  the  origin  of  the  crystal ;  while  the  ordinary 
mode  is  paragenic.  One  form  of  it  is  illustrated  in 
f.  268.  The  middle  portion  had  attained  a  length 
of  half  an  inch  or  more,  and  then  became  genicu- 
lated  simultaneously  at  either  extremity.  These 
geniculations  are  often  repeated  in  rutile,  and  the 
ends  of  the  crystal  are  thus  bent  into  one  another,  and 
occasionally  produce  nearly  regular  prismatic  forms. 

This  metagenic  twinning  is  sometimes  presented 
by  the  successive  layers  of  deposition  in  a  crystal, 
as  in  some  quartz  crystals,  especially  amethyst,  the 
inseparable  layers,  exceedingly  thin,  being  of  oppo- 
site kinds.  So  calcite  crystals  are  sometimes  made 
up  of  twinned  layers,  which  are  due  to  an  oscillatory 
process  of  twinning  attend  ing  the  progress  of  the 
crystal.  In  a  similar  manner,  crystals  of  the  triclinic  feldspars,  albite, 
etc.,  are  often  made  up  of  thin  plates  parallel  to  i-t,  by  oscillatory  compo- 
sition, and  the  face  O,  accordingly,  is  finely  striated  parallel  to  the  edge 
O  A  i-L 


Rutile. 


92 


CRYSTALLOGRAPHY. 


Repeated  twinning. — In  the  preceding  paragraph  one  case  of  repeated 
twinning  has  been  mentioned,  that  of  the  feldspars  ;  it  is  a  case  of  parallel 
repetition  or  parallel  grouping  of  the  successive  crystals.  Another  kind  is 
that  which  is  illustrated  by  f.  295,  297,  311,  where  the  successively 
reversed  individuals  are  not  parallel.  In  this  case  the  axes  may,  however, 
lie  in  a  zone,  as  the  prismatic  twins  of  aragonite,  or  they  may  be  inclined 
to  each  other,  as  in  f .  311,  of  staurolite.  In  all  such  cases  where  the  repeti- 
tion of  the  twinning  tends  to  produce  circular  forms,  as  f .  281,  of  rutile,  the 
number  of  individuals  is  equal  to  the  number  of  times  the  angle  between 
the  two  axial  systems  is  contained  in  360°.  For  example,  five-fold  twins 
occur  in  the  tetrahedrons  of  gold  and  sphalerite,  since  5  x  70°  32'  (the  tetra- 
hedral  angle)  =  360°  (approx.).  A  compound  crystal,  when  there  are  three 
individuals,  is  called  a  Trilling  (Drilling,  Germ.),  where  there  are  four 
individuals,  a  Fourling  (Yierling,  Germ.),  etc. 

Compound  crystals  in  which  twinning  exists  in  accordance  with  two  laws 
at  once  are  of  rare  occurrence ;  an  excellent  example  is  afforded  by  stauro- 
lite, f.  312.  They  have  also  been  observed  on  albite  (f.  333),  orthoclase, 
chalcocite,  and  in  other  less  distinct  cases. 


Examples  of  different  methods  of  Twinning* 

ISOMETRIC  SYSTEM. — With  few  exceptions  the  twins  of  this  system  are  of 
one  kind,  the  twinning  axis  an  octahedral  axis,  and  the  twinning  plane 
consequently  an  octahedral  plane  •  inmost  cases  also  the  latter  coincides 


Gralenite. 


Sphalerite. 


Galenite. 


with  the  composition-face.  Fig.  263  shows  this  kind  as  applied  to  the 
simple  octahedron,  it  is  especially  common  with  the  spinel  group  of  min- 
erals ;  similarly,  f.  269,  a  more  complex  form,  and  also,  f.  270,  a  dodeca- 
hedron twinned  ;  all  these  are  contact  twins.  Fig.  271  is  a  penetration 
twin  following  the  same  law  ;  the  twinning  being  repeated,  and  the  form 
flattened  parallel  to  an  octahedral  face.  Fig.  266,  p.  91,  shows  a  twin  of 


*  A  complete  enumeration  of  the  different  methods  of  twinning  observed  under  the  differ- 
ent systems,  with  detailed  descriptions  and  many  figures,  will  be  found  in  Vol.  II.  of  Rose- 
Sadebeck's  Crystallography  (Angewandce  Krystaliographie,  284  pp.,  8vo,  Berlin,  1876). 


TWIN    CRYSTALS. 


93 


fluorite,  two  interpenetrating  cubes  ;  f.  272  exhibits  a  dodecahedral  twin 
of  sodalite  occurring  in  nature  of  almost  ideal  symmetry,  and  f.  273  is  a 
tetrahedral  twin  of  the  species  tetrahedrite  ;  the  same  law  is  true  for  all. 


272 


Sodalite. 


Tetrahedrite. 


Haiiynite. 


Figs.  274,  275,  276,  are  twins  whose  axes  are  parallel ;  these  forms  are 
possible  only  with  hemihedral  crystals.  The  twinning  axis  is  here  a  dode- 
cahedral axis  and  the  twinning  plane  a  dodecahedral  plane.  The  same 


275 


276 


277 


Pyrite. 


Magnetite. 


method  of  composition  is  often  seen  in  dendritic  crystallizations  of  native 
gold  and  copper,  in  which  the  angle  of  divergence  of  the  branches  is  60° 
and  120°,  the  interfacial  angles  of  a  dodecahedron.  The  brownish-black 
mineral  in  the  mica  from  Pennsbury,  Pa.,  is  magnetite  in  this  form  (f .  277), 
as  first  observed  by  G.  J.  Brush. 

TETRAGONAL  SYSTEM. — The  most  common  method  is  that  where  the  twin- 
ning-plane  is  parallel  to  \-i.  It  is  especially  characteristic  of  rutile  and 
cassiterite.  This  is  illustrated  in  f.  264  and  similarly  in  f.  278.  Fig.  268 
shows  a  similar  twin  of  rutile,  and  in  f.  281  to  283  the  twinning  according 
to  this  law  is  repeated.  In  f.  281  the  vertical  axes  of  the  successive  six 
individuals  lie  in  a  plane,  and  an  enclosed  circle  is  the  result ;  in  f .  282  the 
successive  vertical  axes  form  a  zig-zag  line  ;  there  are  here  four  individuals, 


CRYSTALLOGRAPHY. 


add  four  more  behind,  the  last  (YIII)  uniting  with  the  first  (I),  and  let  it 
be  developed  vertically,  and  the  complex  form  produced  results  in  the 
scalenohedron  twin  of  f.  283.  In  chalcopyrite,  the  octahedron  1,  which  is 


Cassiterite. 


Chalcopyrite. 


Scheelite. 


very  near  a  regular  octahedron  in  angle,  may  be  the  twinning-plane,  and 
forms  are  thus  produced  very  similar  to  f.  263.  With  hernihedral  forms 
twinning  may  take  place  as  shown  in  f.  280,  where  the  axis  of  revolution 


Kutile. 


Rutile. 


is  a  diagonal  axis,  and  the  plane  of  twinning  the  prism  I.  It  is  not  always 
indicated  by  a  re-entering  angle,  but  is  sometimes  only  shown  by  the 
oblique  striations  in  two  directions  meeting  in  the  line  of  contact. 


284 


Rutile. 


Pyrrhotite. 


Another  mode  of  twinning  is  that  occurring  in  leucite,  observed  by  vom 
Rath,  who  showed  the  species  to  be  tetragonal.  The  twinning-plane  is  here 
2-£  (Jahrb.  Min.,  1873,  113.) 


TWIN    CRYSTALS. 


95 


HEXAGONAL  SYSTEM. — In  the  holohedral  division  of  this  system  twins  are 
rare.  An  example  is  furnished  by  pyrrhotite,  f.  284,  where  the  twinning- 
plane  is  the  pyramid  1,  the  vertical  axes  of  the  individual  crystals  being 
nearly  at  right  angles  to  each  other  (O  A  1  =  135?  8').  Another  example 
is  tridymite  *  (see  p.  266),  where  the  twinning-plane  is  either  the  pyramid 
for*. 

285  286  287 


Calcite. 


Calcite. 


Chabazite. 


In  the  species  of  the  rhombohedral  division  twins  are  numerous ;  the 
ordinary  methods  are  the  following :  the  twinning-plane  the  rhombohe- 
dron  R)  f .  285  ;  the  rhombohedron  —  27?,  f.  288  ;  the  rhombohedron  —  \It, 
f .  286.  The  last  mentioned  method  is  common  in  masses  of  calcite,  where  by 
its  frequent  repetition  it  gives  rise  to  thin  lamellae ;  these  are  observed 
often  iii  crystalline  limestones. 


Calcite. 


Calcite. 


Pyrargyrite. 


The  twinning-plane  may  also  be  the  basal  plane,  the  axis  of  revolution 
consequently  the  vertical  axis.  This  is  illustrated  in  f.  287,  a  complex 
penetration  twin  of  chabazite,  also  f .  267  (hematite),  and  in  f.  289,  290. 
It  is  also  common  with  quartz,  the  two  crystals  sometimes  distinct,  and 
joined  by  a  prismatic  plane,  sometimes  interpenetrating  each  other  very 
irregularly,  as  shown  in  f.  265. 


*  G-.  vom  Rath,  Pogg.  Ann.,  oxxxv.  437  ;  clii.  1. 


96 


CRYSTALLOGRAPHY. 


OETHOEHOMBTC  SYSTEM. — In  the  orthorhombic  system  twins  are  exceed- 
ingly common,  and  the  variety  of  methods  is  very  great.  These  may,  how- 
ever, be  brought  into  two  groups,  according  as  the  twinning-plane  is  (1)  a 
prismatic  plane,  vertical  or  horizontal,  or  (2)  an  octahedral  plane.  The 
twinning  is  very  often  repeated,  and  always  in  accordance  with  the  law 
already  stated,  that  the  number  of  individuals  is  determined  by  the  number 
of  times  that  the  angle  of  the  two  axial  systems  is  contained  in  360° 

(a)  Twinning  parallel  to  a  prism  whose  angle  is  approximately  120°. 

1.  Prism  vertical. — The  principal  examples  are  aragonite,  I  A  /  =  116° 
10';  cerussite,  /A  1=  117°  13' ;  witherite,  /A  /  =  118°  30';  bromlite, 
1 A  I  =  118°  50' ;  chalcocite,  /  A  1  ='  119°  35' ;  stephanite,  /  A  1  =  115° 
39';  dyscrasite,  /A/—  119°  59'.  Figs.  291,  292,  represent  twins  of  ara- 
gonite in  accordance  with  this  law.  Figs.  293,  294,  show  cross-sections  of 


the  two  prisms  of  the  preceding  figures,  in  the  latter  the  form  is  hexagonal, 
though  not  regularly  so.     Fig.  295  i 


is  a  cruciform  twin  of  the  same  species. 


291 


292 


il 


A 


295 


294 


Aragonite. 


Aragonite. 


ii 


Aragonite. 


2.  Prism  horizontal ;  that  is,  a  macrodome. — Examples :  arsenopyrite, 
14  A  14  =  120°  46' ;  leadhillite,  l-l  A  14  =  119°  20' ; 
humite,  type  1. 

3.  Prism  horizontal  ;  that  is,  a  brachydome. — 
Examples  :  manganite,  14  A  14  =  122°  50'  (f.  296) ; 
chrysoberyl,  34  A  34  (f.  300)  =120°  13'  ;  columbite, 
24  A  24  =  117°  20'. 

In  all  these  cases  there  is  a  strong  tendency  toward 
repetition  of  the  twinning,  by  which  forms  often  stel- 
late, sometimes  apparently  hexagonal,  result.  These 
forms  are  illustrated  in  the  following  figures  :  f.  297 
is  of  witherite ;  f .  298  a  crystal  of  leadhillite,  in  its 
twinned  form  of  very  rhombohedral  aspect.  Figs. 
.299  and  300  are  both  chrysoberyl,  where  34  is  the 
twinning-plane  ;  six-rayed  twins  are  very  common  in 
this  species. 
The  genesis  of  these  forms  is  further  illustrated  by  the  following  cross- 


Manganite. 


TWIN   CRYSTALS. 


97 


sections.     Fig.  301  shows  a  cross-section  of  a  cerussite  twin,  and  f.  302  one 
of  the  crystal  of  leadhillite  figured  above  (f.  298). 


297 


Witherite. 


Leadhillite. 


Chrysoberyl. 


Chrysoberyl. 


In  f .  303,  three  rhombic  prisms,  /,  of  aragonite,  are  combined  about  their 
acute  angles,  the  dotted  lines  showing  the  outlines  of  the  prisms,  and  the 
cross  lining  the  direction  of  the  brachy diagonal ;  and  in  f..  304,  four  are 
similarly  united.  In  f .  305,  three  similar  prisms,  /,  are  combined  about  the 


301 


Cerussite. 


obtuse  angle.  This  twin  combination  may  take  the  form  of  a  hexagonal 
prism,  with  or  without  re-entering  angles  ;  of  a  three-rayed  twin,  like  f. 
301,  and  if  a  penetration-twin,  of  a  composite  prism,  like  f.  306  (the  num- 
bering of  the  parts  showing  the  relation),  or  a  six-rayed  twin.  In  all  these 
cases  the  stellate  form  depends  on  the  extension  of  the  individuals  beyond 
the  normal  limits. 

(b)  Prismatic  angle  approximately  that  of  the  regular  octahedron,  109° 
28'.     An  example  is  furnished  by  the  species  staurolite  (f.  307),  where  the 
7 


98 


CEYSTALLOGRAPHT. 


307 


308 


twinning-plane  is  t'-f,  and  the  corresponding  prismatic  angle  is  109°  14' 

(over  i-%,  or  70°  46'  over  i-i). 
Another  example  is  furnished 
by  marcasite,  whose  prismatic 
angle  is  106°  5'.  The  twins 
are  generally  compound,  the 
repetition  with  the  twinning- 
plane  sometimes  parallel, 
sometimes  oblique,  see  p.  225. 
In  f.  308  the  compound  crys- 
tal consists  of  five  individuals, 
since  five  times  73°  55'  is  ap- 
proximately equal  to  360°. 
Examples  are  furnished  by 
In  the  latter  case 


Staurolite. 


Marcasite. 


(<?)  Prismatic  angle  approximately  90°. 
bournonite,  /  A  /  =  91°  12',  see  p.  232,  and  stauroHte. 
the  twinning-plane  is  a  brachydome,  f-£,  and  the  angle  is  91°  18' ;  the  form 
is  shown  in  f.  309,  it  being  that  of  a  nearly  rectangular  cross.  See  also 
phillipsite,  p.  323. 

2.  The  twinning-plane  may  be  also  an  octahedral  plane.  An  excellent 
example  is  furnished  by  Staurolite,  where  the  twinning-plane  is  f -f  (f .  310). 
The  crystals  cross  at  angles  of  nearly  120°  and  60°,  hence  the  form  in  f. 
311,  consisting  of  three  individuals  (trilling)  forming  a  six-rayed  star.  In 
f.  312  both  this  method  of  twinning  and  that  mentioned  above  are  com- 


Staurolite. 


310 


311 


Staurolite. 


Staurolite. 


312 


Staurolite. 


bined.  There  are  thus  for  the  species  Staurolite  three  methods  of  twin- 
ning, parallel  to  i-f,  tof-£,  and  to  f-~.  If  the  occurring  prism  is  made  *-}, 
then  the  three  twimiing-planes  become  I;  l-£,  1,  or  fundamental  planes,  as 
is  usually  true. 

MoNocLiNio  SYSTEM. — The  following  examples  comprise  the  more  com- 
monly occurring  methods  of  twinning  in  this  system. 

(a)  The  twinning-plane  is-  the  orthopinacoid  (i-i).  This  is  true  in  the 
case  of  the  common  twins  of  orthoclase  (f.  318),  called  the  Carlsbad  twins. 
The  axis  of  revolution  is  normal  to  i-i  (see  also  p.  90),  while  the  two 
crystals-  are  united  by  the  clinopinacoid,  which  is  consequently  the  compo- 
sition-face. These  twins  may  be  either  right-  or  left-handed  (f.  318  or 
f.  319),  according  as  the  right  or  left  half  of  the  simple  form  (f.  317)  has 
been  revolved. 


TWIN   CRYSTALS. 


99 


Fig.  313,  of  pyroxene,  is  another  familiar  example  ;  so  also  f.  314,  of  which 
f.  315  is  the  simple  form.  Fig.  320  is  a  twin  of  scolecite,  where  the  twin 
structure  is  shown  by  the  striations  on  the  clinopinacoid. 


313 


315 


Amphibole. 


Scolecite. 


Malachite. 


A  form  of  penetration-twin,  with  i-i  the  twinning-plane,  is  shown  in 
f.  321  (from  von  Lang).     The  mode  of  combi- 
nation and  cross-penetration  of  the  two  crystals  321 
1,  2,  is  illustrated  in  f.  322 ;  it  is  a  medial  section 
of  f.  321  from  front  to  back. 

(b)  The    twinning-plane    may    also    be    the 
basal  plane.     This  is  common  with  orthoclase 
(f.  324);    also  with  gypsum  (f.  323).      It  has 
also  been  observed   by  the  author  in  chondro- 
dite,  type  II  and  III,  from  Brewster,  N.  Y.,  see 
p.  305. 

(c)  Figs.  325,  326.  327  show  another  method 
of  twinning  of  orthoclase  parallel  to  the  clino- 
dome,  24.      These  twins  are  peculiar  in  that 
they    form    nearly    rectangular   prisms,    since 

0  A  2-1  =135°  3^'.  They  are  common  among  the  orthoclase  crystals  from 
Baveno,  and  hence  are  called  Baveno  twins.  This  method  of  twinning  is 
also  common  with  the  amazon-stone  of  Pike's  Peak. 

The  union  of  four  crystals  of  this  kind  produces  the  form  represented  in 
f.  325  ;  and  the  same,  by  penetration,  develops  the  penetration-twin  of 
f .  327  (from  v.  Rath),  which  apparently  consists  of  four  pairs  of  twins,  but 
may  be  regarded  as  made  by  the  crossvpenetration  of  the  crystals  of  two 
pairs,  or  of  the  four  of  f.  325. 

Forms  like  f.  325  may  have  one  of  the  four  parts  undeveloped  and  so 
consist  of  three  united  crystals,  and  also  the  other  parts,  as  in  such  com- 
pound twins  generally,  may  be  very  unequal. 

Twins  corresponding  to  those  of  the  orthorhombic  system,  where  tho 
twinning-plane  is  a  prism  whose  angle  is  nearly  120°,  have  been  observed 
by  vom  Rath  in  humite,  types  II  and  III. 

TRICLINIC  SYSTEM. — In  the  twins  of  the  triclinic  system,  the  three  axes 


100 


CRYSTALLOGRAPHY. 


may  be  axes  of  revolution,  in  which  case  the  twinning-planes  are  not  occur- 
ring crystallographic  planes ;  or,  the  pinacoid  planes  may  be  the  planes  of 
twinning  and  the  normals  to  them  the  axes  of  revolution.  Some  of  the 
cases  are  illustrated  in  the  following  figures  of  albite.  In  f.  329  the 
brachy  pinacoid  (i-$)  is  the  twinning-plane ;  f.  328  is  the  same,  but  it  is  a 
penetration- twin ;  this  is  the  most  common  method  of  twinning  with  this 
species. 


323 


324 


Gypsum. 


Orthoclase. 


Orthoclase. 


In  f.  332  the  vertical  axis  is  the  twinn ing-axis.  Fig.  333  (from  G.  Rose) 
is  a  double  twin,  the  two  halves  of  which  are  like  f.  328,  but  they  are 
twinned  together  like  f.  332.  It  happens  in  albite  that  the  plane  angles 


328 


on  i-i,  made  by  the  edges  7"  A  0  and  7 "A  1  differ  but  37'  (the  former  being 
116°  26',  the  latter  115°  55'),  and  hence  it  is  that  in  the  twin  0  and  1  fall 
nearly  into  one  plane. 


TWIN   CRYSTALS. 


101 


Composition  parallel  to  0,  where  the  revolution  is  on  a  horizontal  axis 
normal  to  the  shorter  diagonal  of  O,  is  ex- 
emplified in  f.  334  (from  G.  Rose).  Both 
right-  and  left-handed  twins  of  this  kind 
occur ;  also  double  twins  in  which  this 
method  is  combined  with  twinning  (like 
that  in  f .  329,  330),  parallel  to  i-L 

A  thorough  discussion  of  the  method  of 
twinning  in  the  triclinic  system  has  been 
given  by  Schrauf  in  his  monograph  of  the 
species  brochantite  (Ber.  Ak.,  Wlen,  Ixvii.,  275,  1873). 


Albite. 


REGULAR  GROUPING  OF  CRYSTALS. 

Connected  with  the  subject  of  twin  crystals  is  that  of  the  parallel  posi- 
tion of  associated  crystals  of  the  same  species,  or  of  different  species. 
Crystals  of  the  same  species  occurring  together  are  very  commonly 
in  parallel  position.  In  this  way  large  crystals  are  sometimes  built  up  of 
smaller.individuals  grouped  together  with  corresponding  planes  parallel. 
Tiiis  parallel  grouping  is  often  seen  in  crystals  as  they  lie  on  the  support- 
ing rock.  On  glancing  the  eye  over  a  surface  covered  with  crystals,  a 
reflection  from  one  face  will  often  be  accompanied  with  reflections  from  the 
corresponding  face  in  each  of  the  other  crystals,  showing  that  the  crystals 
are  throughout  similar  in  their  positions. 

Crystals  of  different  species  often  show  the  same  tendency  to  parallelism 
in  mutual  position.  This  is  true  most  frequently  of  species  which,  from 
similarity  of  form  and  composition,  are  said  to  be  isomorphous  (see  p.  177). 
Crystals  of  albite,  implanted  on  a  surface  of  orthoclase,  are  sometimes  an 
example  of  this ;  crystals  of  hornblende  and  pyroxene,  and  of  various  kinds 
of  mica  are  also  at  times  observed  associated  in  parallel  position. 

The  same  relation  of  position  also  occasionally  occurs  where  there  is  no 
connection  in  composition,  as  the  crystals  of  rutile  on  tabular  crystals  of 
hematite,  the  vertical  axes  of  the  former  coinciding  with  the  lateral  axes 
of  the  latter.  Breithaupt  has  figured  crystals  of  calcite,  whose  rhombo- 


hedral  faces  (—  %R)  had  a  series  of  quartz  crystals  upon  them,  all  in 
parallel  position  (f .  335) ;  and  Frenzel  and  vom  Rath  have  described  the 
same  association  where  three  such  quartz  crystals,  one  on  each  rhombo- 
hedral  face,  entirely  enveloped  the  calcite,  and  uniting  with  re-entering 


102  CRYSTALLOGRAPHY. 

angles  formed  pseudo-twins  (rather  trillings)  of  quartz  after  calcite.  The 
author  has  described  a  similar  occurrence  from  "  Specimen  Mountain,"  in 
the  Yellowstone  Park ;  the  form  is  shown  in  f.  336.  (Am.  J.  Sci.,  III., 
xii.,  1876.) 


IRREGULARITIES   OF   CRYSTALS. 

The  laws  of  crystallization,  when  unmodified  by  extrinsic  causes,  should 
produce  forms  of  exact  symmetry ;  the  angles  being  not  only  equal,  but 
also  the  homologous  faces  of  crystals  and  the  dimensions  in  the  directions 
of  like  axes.  This  symmetry  is,  however,  so  uncommon,  that  it  can 
hardly  be  considered  other  than  an  ideal  perfection.  Crystals  are  very 
generally  distorted,  and  often  the  fundamental  forms  are  so  completely  dis- 
guised, that  an  intimate  familiarity  with  the  possible  irregularities  is  re- 
quired in  order  to  unravel  their  complexities.  Even  the  angles  may 
occasionally  vary  rather  widely. 

The  irregularities  of  crystals  may  be  treated  of  under  several  heads :  1, 
Imperfections  of  surface  /  2,  Variations  of  form  and  dimensions  /  3, 
Variations  of  angles  ;  4,  Internal  imperfections  and  impurities. 

I.  IMPERFECTIONS  IN  THE  SURFACES  OF  CRYSTALS. 

1.  Striations  or  angular  elevations  arising  from  oscillatory  combina- 
tions.— The  parallel  lines  or  furrows  on  the  surfaces  of  crystals  are  called 
strice,  and  such  surfaces  are  said  to  be  striated. 

Each  little  ridge  on  a  striated  surface  is  enclosed  by  two  narrow  planes 
more  or  less  regular.  These  planes  often  correspond  in  position  to  differ- 
ent planes  of  the  crystal,  and  we  may  suppose  these  ridges  to  have  been 
formed  by  a  continued  oscillation  in  the  operation  of  the  causes  that  give 
rise,  when  acting  uninterruptedly,  to  enlarged  planes.  By  this  means,  the 
surfaces  of  a  crystal  are  marked  in  parallel  lines,  with  a  succession  of  nar- 
row planes  meeting  at  an  angle  and  constituting  the  ridges  referred  to. 

This  combination  of  different  planes  in  the  forma- 
337  tlon  of  a  surface  has  been  termed  oscillatory  com- 

bination. The  horizontal  striae  on  prismatic  crystals 
of  quartz  are  examples  of  this  combination,  in 
which  the  oscillation  has  taken  place  between  the 
prismatic  and  pyramidal  planes.  As  the  crystals 
lengthened,  there  was  apparently  a  continual  effort 
to  assume  the  terminal  pyramidal  planes,  which  effort 
was  interruptedly  overcome  by  a  strong  tendency  to 
an  increase  in  the  length  of  the  prism.  In  this 
manner,  crystals  of  quartz  are  often  tapered  to  a 
point,  without  the  usual  pyramidal  terminations. 
Magnetite.  Other  examples  are  the  striation  on  the  cubic  faces 

of  pyrite  parallel  with  the  intersections  of  the  cube 

with  the  planes  of  the  pyritohedron ;    also  the   striations   on   magnetite 
(f.  337)  due  to  the  oscillation  between  the  octahedron  and  dodecahedron. 


IRREGULARITIES    OF    CRYSTALS.  103 

Prisms  of  tourmaline  are  very  commonly  bounded  vertically  "by  three  convex 
surfaces,  owing  to  an  oscillatory  combination  of  the  planes  /and  i-2. 

Faces  of  crystals  are  often  marked  with  angular  elevations  more  or  less 
distinct,  due  sometimes  also  to  oscillatory  combination.  Octahedrons  of 
ftuorite  are  common  which  have  for  each  face  a  surface  of  minute  cubes, 
proceeding  from  an  oscillation  between  the  cube  and  octahedron.  This  is 
a  common  cause  of  drusy  surfaces  with  the  crystals  of  many  minerals. 

2.  Striations from  oscillatory  composition. — The  striations  of  the  plane 
O  of  albite  and  other  triclinic  feldspars,  and  of  the  rhombohedral  surfaces 
some  calcite,  have  been  attributed,  on  p.  91,  to  oscillatory  twinning. 

3.  Markings  from  erosion  and  other  causes. — It  is  not  uncommon  that 
the  faces  of  crystals  are  uneven,  or  have  the  crystalline  structure  developed 
as  a  consequence  of  etching  by  some  chemical  agent.     Cubes  of  galenite 
are  often  thus  uneven,  and  crystals  of  lead  sulphate  or  lead  carbonate  are 
sometimes  present  as  evidence  with  regard  to  the  cause.     Crystals  of  numer- 
ous other  species,  even  of  corundum,  spinel,  quartz,  etc.,  sometimes  show  the 
same  result  of  partial  change  over  the  surface — often  the  incipient  stage  in 
a  process  tending  to  a  tinal  removal  of  the  whole  crystal.     Interesting  in- 
vestigations have  been  made  by  various  authors  on  the  action  of  solvents  011 
different  minerals,  the  actual  structure  of  the  crystals  being  developed  in 
this  way.     These  are  referred  to  again  in  another  place  (p.  118). 

The  markings  on  the  surfaces  of  crystals  are  not,  however,  always  to  be 
ascribed  to  etching.  In  most  cases  etchings,  as  well  as  the  minute  angular 
elevations  upon  the  planes,  are  a  part  of  the  original  molecular  growth  of 
the  crystal,  and  often  serve  to  show  the  successive  stages  in  its  history. 
They  are  the  imperfections  arising  from  an  interrupted  or  disturbed  de- 
velopment of  the  form,  the  perfectly  smooth  and  even  crystalline  faces 
being  the  result  of  completed  action  free  from  disturbing  causes.  Ex- 
amples of  the  marking  referred  to  occur  on  the  crystals  of  most  minerals, 
and  conspicuously  so  on  the  pyramidal  planes  of  quartz. 

The  development  of  this  subject  belongs  rather  to  crystallogeny  ;  refer- 
ence may,  however,  be  made  here  to  the  memoirs  of  Scharif,  bearing  011 
this  subject,  especially  one  entitled  "  Ueber  den  Quarz,  II.,  dei  Ueber- 
gangsflachen,"  Frankfort,  1874;  also  to  the  Crystallography  of  Sadebeck 
(for  title  see  Introduction). 

It  follows  from  the  symmetry  of  crystallization  that  like  planes  should 
be  physically  alike,  that  is  in  regard  to  their  surface  character  ;  it  thus 
often  happens  that  on  all  the  crystals  of  a  species  from  a  given  locality,  or 
perhaps  from  all  localities,  the  same  planes  are  etched  or  roughened  alike. 
For  example,  on  crystals  of  datolite  from  Bergen  Hill,  the  plane  —  2-i 
is  almost  uniformly  destitute  of  lustre;  there  is  much  uniformity  on  the 
crystals  of  quartz  in  this  respect. 

4.  Curved  surfaces  may  result  from  (a)  oscillatory  combination  ;  or  (b) 
some  independent  molecular  condition  producing  curvatures  in  the  laminae 
of  the  crystal ;  or  (V)  from  a  mechanical  cause. 

Curved  surfaces  of  the  first  kind  have  been  already  mentioned,  p.  102. 
A  singular  curvature  of  this  nature  is  seen  in  f.  339,  of  calcite  ;  and  another 
in  the  same  mineral  in  the  lower  part  of  f.  338,  in  which  traces  of  a  scaleno- 
hedral  form  are  apparent  which  was  in  oscillatory  combination  with  the 
prismatic  form. 


104 


CRYSTALLOGRAPHY. 


Curvatures  of  the  second  kind  sometimes  have  all  the  faces  convex.  This 
is  the  case  in  crystals  of  diamond  (f.  340),  some  of  which  are  almost 
spheres.  The  mode  of  curvature,  in  which  all  the  faces  are  equally  con- 
vex, is  less  common  than  that  in  which  a  convex  surface  is  opposite  and 
parallel  to  a  corresponding  concave  surface.  Rhombohedrons  of  siderite 
(see  p.  381)  are  usually  thus  curved.  The  feathery  curves  of  frost  on  win- 
dows and  the  flagging  stones  of  pavements  in  winter  are  other  examples  of 
curves  of  the  second  kind.  The  alabaster  rosettes  from  the  Mammoth 
Cave,  Ky.,  are  similar. 


838 


339 


340 


Caleite. 


Calcite. 


Diamond. 


third  kind  of  curvature  is  of  mechanical  origin.     In  many  species 

crystals  appear  as  if  they  had  been  broken 
transversely  into  many  pieces,  a  slight  dis- 
placement of  which  has  given  a  curved  form 
to  the  prism.  This  is  common  in  tourmaline 
and  beryl.  The  beryls  of  Monroe,  Conn., 
often  present  these  interrupted  curvatures, 
as  represented  in  f .  341 . 

Crystals   not   un frequently  occur   with   a 
deep    pyramidal   depression   occupying   the 


Beryl,  Monroe,  Conn. 


}S 
place  of  each  plane,  as  is  often  observed  in  common  salt,  alum,  and  sulphur. 

This  is  due  in  part  to  their  rapid  growth. 


II.  VARIATIONS  IN  THE  FORMS  AND  DIMENSIONS  OF  CRYSTALS. 

The  simplest  modification  of  form  in  crystals  consists  in  a  simple  varia- 
tion in  length  or  breadth,  without  a  disparity  in  similar  secondary  planes. 
The  distortion,  however,  extends  very  generally  to  the  secondary  planes, 
especially  when  the  elongation  of  a  crystal  takes  place  in  the  direction  of  a 
diagonal,  instead  of  the  crystallographic  axes.  In  many  instances,  one  or 
more  planes  are  obliterated  by  the  enlargement  of  others,  proving  a  source 
of  much  perplexity  to  the  student.  The  interfacial  angles  remain  constant, 
unaffected  by  these  variations  in  form.  These  changes  in  form  often  give 
rise  to  what  is  called  by  Sadebeck  pseudo-symmetry  •  the  distorted  forms 
of  one  system  appearing  similar  to  the  normal  forms  of  another.  (Compare 
the  descriptions  of  the  following  figures.)  As  most  of  the  difficulties  in  the 


IRREGULARITIES    OF    CRYSTALS. 


105 


study  of  crystals  arises  from  these  distortions,  this  subject  is  one  of  great 
importance. 

Figs.  342  to  353  represent  examples  from  the  isometric  system. 

A  cube  lengthened  or  shortened  along  one  axis  becomes  a  right  square 

Erism,  and  if  varied  in  the  direction  of  two  axes  is  changed  to  a  rectangu- 
ir  prism.  Cubes  of  pyrite,  galenite,  fluorite,  etc.,  are  generally  thus  dis- 
torted. It  is  very  unusual  to  find  a  cubic  crystal  that  is  a  true  symmetrical 
cube.  In  some  species  the  cube  or  octahedron  (or  other  isometric  form)  is 
lengthened  into  a  capillary  crystal  or  needle,  as  happens  in  cuprite  and 
pyrite. 

An  octahedron  flattened  parallel  to  a  face,  or  in  the  direction  of  a  trigonal 
interaxis,  is  reduced  to  a  tabular  crystal  (f.  342).  If  lengthened  in  the 
same  direction,  it  takes  the  form  in  f.  343  ;  or  if  still  farther  lengthened 
to  the  obliteration  of  A',  it  becomes  an  acute  rhombohedron  (same  figure). 


342 


344 


When  an  octahedron  is  extended  in  the  direction  of  a  line  between  two 
opposite  edges,  or  that  of  a  rhombic  interaxis,  it  has  the  general  form  of 
a  rectangular  octahedron ;  and  still  farther  extended,  as  in  f .  344,  it  is 
changed  to  a  rhombic  prism  with  dihedral  summits  (spinel,  fluorite,  magne- 
tite). The  figure  represents  this  prism  lying  on  its  acute  edge. 

The  dodecahedron  lengthened  in  the  direction  of  a  diagonal  between  the 


345 


346 


347 


348 


obtuse  solid  angles,  that  is,  that  of  a  trigonal  interaxis,  becomes  a  six- 
sided  prism  with  three-sided  summits,  as  in  f.  345  ;  and  shortened  in  the 
same  direction  is  a  short  prism  of  the  same  kind  (f.  346).  Both  resemble 
rhombohedral  forms  and  are  common  in  garnet  and  zinc  blende.  When 
lengthened  in  the  direction  of  one  of  the  cubic  axes,  it  becomes  a  square 
prism  with  pyramidal  summits  (f.  347),  and  shortened  along  the  same  axis 
it  is  reduced  to  a  square  octahedron,  with  truncated  basal  angles  (f.  348). 


106 


CRYSTALLOGRAPHY. 


The  trapezohedron  is  still  more  disguised  by  its  distortions.  When  elon- 
gated in  the  line  of  a  trigonal  interaxis,  it  assumes  the  form  in  f.  349  ;  and 
still  farther  lengthened,  to  the  obliteration  of  some  of  the  planes,  becomes 
a  scalene  dodecahedron  (f.  350).  This  has  been  observed  in  fluor  spar. 
Only  twelve  planes  are  here  present  out  of  the  twenty -four.  Threads  of 
native  gold  from  Oregon,  are  strings  of  crystals  presenting  the  form  of  this 
very  acute  rhombohedron,  with  the  other  planes  of  the  trapezohedron  2-2 
(the  scalenohedral  and  the  terminal  obtuse  rhombohedral)  quite  small  at 
the  extremities. 

If  the  elongation  of  the  trapezohedron  takes  place  along  a  cubic  axis,  it 
becomes  a  double  eight-sided  pyramid  with  four-sided  summits  (f.  351) ;  or 
if  these  summit  planes  are  obliterated  by  a  farther  extension,  it  becomes  a 
complete  eight-sided  double  pyramid  (f.  352). 


850 


A  scaleno-dodecahedron  of  calcite  is  shown  distorted  in  f.  353,  which  ap- 
pears, however,  to  be  an  eight-sided  prism,  bounded  laterally  by  the  planes 
7?,  I3, 13,  and  R,  and  their  opposites,  and  terminated  by  the  remaining  planes. 
The  following  figures  of  quartz  (f.  354,  355)  represent  distorted  forms  of 
this  mineral,  in  which  some  of  the  pyramidal  faces  by  enlargement  dis- 
place the  prismatic  faces,  and  nearly  obliterate  some  of  the  other  pyramidal 
faces ;  see  also  f.  336. 


353 


354 


355 


Calcite. 


Quartz. 


Quartz. 


Fig.  356  is  a  distorted  crystal  of  apatite  ;  the  same  is  shown  in  f.  357 
with  the  normal  symmetry.  The  planes  between  O  and  the  right  I  are 
enlarged,  while  the  corresponding  planes  below  are  in  part  obliterated. 


IRREGULARITIES   OF   CRYSTALS. 


107 


By  observing  that  similar  planes  are  lettered  alike,  the  correspondence  of 
the  two  figures  will  be  understood. 

In  deciphering  the  distorted  crystalline  forms  it  must  be  remembered 
that  while  the  appearance  of  the  crystals  may  be  entirely  altered,  the  angles 
remain  the  same  ;  moreover,  like  planes  are  physically  alike,  that  is,  alike 
in  degree  of  lustre,  in  striations,  and  so  on. 


356 


357 


Apatite. 


Apatite. 


In  addition  to  the  variations  in  form  which  have  just  been  described,  still 
greater  irregularities  are  due  to  the  fact  that,  in  almost  all  cases,  crystals  in 
nature  are  attached  either  to  other  crystals  or  to  some  rock  surface,  and  in 
consequence  of  this  are  only  partially  developed.  Thus  quartz  crystals  are 
generally  attached  by  an  extremity  of  the  prism,  and  hence  have  only  one 
set  of  pyramidal  planes  ;  perfectly  formed  crystals,  as  those  from  Herkimer 
Co.,  N.  Y.,  having  the  double  pyramid  complete,  are  rare.  The  same 
statement  may  be  made  for  nearly  all  species. 


13*1.  VARIATIONS  IN  THE  ANGLES  OF  CRYSTALS. 


The  greater  part  of  the  distortions  described  occasion  no  change  in  the 
interfacial  angles  of  crystals.  But  those  imperfections  that  produce  con- 
vex, curved,  or  striated  faces,  necessarily  cause  such  variations.  Further- 
more, circumstances  of  heat  or  pressure  under  which  the  crystals  were 
formed  may  sometimes  cause  not  only  distortion  in  form,  but  also  some 
variation  in  angle.  The  presence  of  impurities  at  the  time  of  crystallization 
may  also  have  a  like  effect. 

Still  more  important  is  the  change  in  the  angles  of  completed  crystals 
which  is  caused  by  subsequent  pressure  on  the  matrix  in  which  they  were 
formed,  as,  for  example,  the  change  which  may  take  place  during  the  more 
or  less  complete  metamorphism  of  the  enclosing  rock. 

The  change  of  composition  resulting  in  pseudomorphous  crystals  (see 
p.  113)  is  generally  accompanied  by  an  irregular  change  of  angle,  so  that 
the  pseudomorphs  of  a  species  vary  much  in  angle. 

In  general  it  is  safe  to  affirm  that,  with  the  exception  of  the  irregularities 


108  CRYSTALLOGRAPHY. 

arising  from  imperfections  in  the  process  of  crystallization,  or  from 
changes  produced  subsequently,  variations  in  the  angles  are  rare,  and  the 
constancy  of  angle  alluded  to  on  p.  87  is  the  universal  law.* 

In  cases  where  a  greater  or  less  variation  in  angle  has  been  observed  in 
the  crystals  of  the  same  species  from  different  localities,  the  cause  for  this 
can  usually  be  found  in  a  difference  of  chemical  composition.  In  the  case 
of  isomorphous  compounds  it  is  well  known  that  an  exchange  of  correspond- 
ing chemically  equivalent  elements  may  take  place  without  a  change  of 
form,  though  usually  accompanied  with  a  slight  variation  in  the  funda- 
mental angles. 

The  effect  of  heat  upon  the  form  of  crystals  is  alluded  to  upon  p.  164. 


IY.  INTERNAL  IMPERFECTIONS  AND  IMPURITIES. 

,fr 

The  transparency  of  crystals  is  often  destroyed  by  disturbed  crystalliza- 
tion, or  by  impurities  taken  up  from  the  solution  during  the  process  of 
crystallization.  These  impurities  may  be  simply  coloring  ingredients,  or  they 
may  be  inclosed  particles,  fluid  or  solid,  visible  to  the  eye  or  under  the 
microscope.  The  coloring  ingredients  may  vary  in  the  course  of  formation 
of  the  crystals,  and  thus  layers  of  different  colors  result ;  the  tourmaline 
crystals  of  Chesterfield,  Mass.,  have  a  red  centre  and  blue  exterior ;  others 
from  Elba  are  sometimes  light-green  below  and  black  at  the  extremity ; 
many  other  examples  might  be  given. 

The  subject  of  the  fluid  and  solid  inclosures  in  crystals  is  one  to  which 
much  attention  has  been  directed  of  late  years.  Attention  was  early  called 
to  its  importance  by  Brewster,  who  described  the  presence  of  fluids  in 
quartz,  topaz,  beryl,  chrysolite,  and  other  minerals.  In  later  years  the  mat- 
ter has  been  more  thoroughly  studied  by  Sorby,  Zirkel,  Vogelsang,  Fischer, 
Kosenbusch,  and  many  others.  (See  Literature,  p.  111.) 

Many  crystals  contain  empty  cavities ;  in  others  the  cavities  are  filled 
sometimes  with  water,  or  with  the  salt  solution  in  which  the  crystal  was 
formed,  and  not  infrequently,  especially  in  the  case  of  quartz,  with  liquid 
carbonic  acid,  as  first  proved  by  Vogelsang,  and  recently  followed  out  by 
Hartley.  These  liquid  inclosures  are  marked  as  such,  in  many  cases,  by 
the  presence  in  the  cavity  of  a  movable  bubble. 

The  solid  inclosures  are  almost  infinite  in  their  variety.  Sometimes  they 
are  large  and  distinct,  and  can  be  referred  to  known  mineral  species,  as  the 
scales  of  hematite  to  which  the  peculiar  character  of  aventurine  feldspar  is 
due.  Magnetite  is  a  very  common  impurity  for  many  minerals,  appearing, 
for  example,  in  the  Pennsbury  mica;  quartz  is  also  often  mechanically 
mixed,  as  in  staurolite  and  gmelinite.  On  the  other  hand,  quartz  crystals 
very  commonly  inclose  foreign  material,  such  as  chlorite,  tourmaline,  rutile, 
hematite,  asbestos,  and  many  other  minerals. 


*  Reference  must  be  made  here  to  the  discussion  by  Scacchi  of  the  principle  of  ' '  Polysym- 
metry."  (Atti  Accad.  Napoli,  i.,  1864.)  See  also  Hirschwald,  Zur  Kritik  des  Leucitsy  stems, 
Tsch.  Min.  Mitth.,  1875,  227. 


IRREGULARITIES    OF    CRYSTALS. 


109 


358 


The  inclosures  may  also  consist  of  a  heterogeneous  mass  of  material ;  as 
the  granitic  matter  seen  in  orthoclase  crystals  in  a  porphyritic  granite  ;  or 
the  feldspar,  quartz,  etc.,  sometimes  inclosed  in 
large  coarse  crystals  of  beryl,  occurring  in  granite 
veins. 

An  interesting  example  of  the  inclosure  of  one 
mineral  by  another  is  afforded  by  the  annexed 
figures  of  tourmaline,  enveloping  orthoclase  (E.  H. 
Williams,  Am.  J.  Sci.,  III.,  xi.,  273,  1876).  Fig. 
358  shows  the  crystal  of  tourmaline  ;  and  cross-sec- 
tions of  it  at  the  points  indicated  (a,  &,  c)  are  given 
by  f.  359,  360,  361.  The  latter  show  that  the  feld- 
spar increases  in  amount  in  the  lower  part  of  the 
crystal,  the  tourmaline  being  merely  a  thin  shell. 
Similar  specimens  from  the  same  locality  (Port 
Henry,  Essex  Co.,  N".  Y.)  show  that  there  is  no  ne- 
cessary connection  between  the  position  of  the  tour- 
maline and  that  of  the  feldspar. 

Similar  occurrences  are  those  of  trapezohedrons 
of  garnet,  where  the  latter  is  a  mere  shell,  enclosing 
calcite,   or  sometimes  epidote.       Analogous  cases 
have  been  explained  by  some  authors  as  being  due  to  partial  pseudomorph- 
ism, the  alteration  progressing  from  the  centre  outward. 

359 


The  microscopic  crystals  observed  as  inclosures  may  sometimes  be 
referred  to  known  species,  but  more  generally  their  true  nature  is  doubtful. 
The  term  microUtes,  proposed  by  Vogelsang,  is  often  used  to  designate  the 


minute  inclosed  crystals;  they  are  generally  of  needle-like  form,  some- 
times quite  irregular,  and  often  very  remarkable  in  their  arrangement  and 
groupings  ;  some  of  them  are  exhibited  in  f.  367  and  f.  368,  as  explained 


110 


CRYSTALLOGRAPHY. 


below.  Trichite  and  belcnite  are  names  introduced  by  Zirkel ;  the  former 
name  is  derived  from  0pl£,  hair,  the  forms,  like  that  in  f.  362,  are  common 
in  obsidian.  "Where  the  minute  individuals  belong  to  known  species  they 
are  called,  for  example,  feldspar  microlites,  etc. 

Crystallites  is  an  analogous  term  which  is  intended  by  Vogelsang  to  cover 
those  minute  forms  which  have  not  the  regular  exterior  form  of  crystals, 
but  may  be  considered  as  intermediate  between  amorphous  matter  and  true 
crystals.  Some  of  the  forms,  figured  by  Vogelsang,  are  shown  in  f.  363  to 
366 ;  they  are  often  observed  in  glassy  volcanic  rocks,  and  also  in  furnace 
A  series  of  names  have  been  given  to  varieties  of  crystallites,  such 


as  globulites,  margarites,  etc.' 

the  microscopic  in  closures  may  also  be  of  an  irregular  glassy  nature  ;  a 
kind  that  exists  in  crystals  which  have  formed  from  a  melted  mass,  as  lavas, 
or  the  slag  of  iron  furnaces. 

In  general,  it  may  be  said  that  while  the  solid  inclosures  occur  sometimes 
quite  irregularly  in  the  crystals,  they  are  more  generally  arranged  with 
some  evident  reference  to  the  symmetry  of  the  form,  or  planes  of  the 
crystals.  Examples  of  this  are  shown  in  the  following  figures:  f.  367  ex- 


368 


Augite. 


Leucite. 


Calcite. 


hibits  a  crystal  of  augite,  inclosing  magnetite,  feldspar  and  nephelito 
microlites,  etc.,  and  f.  368  shows  a  crystal  of  leucite,  a  species  whose 
crystals  very  commonly  inclose  foreign  matter.  Fig.  369  shows  a  section 
of  a  crystal  of  calcite,  containing  pyrite. 


Andalusite. 


Another  striking  example  is  afforded  by  andalusite,  in  which  the  inclosed 
impurities  are  of  considerable  extent  and  remarkably  arranged.  Fig.  370 
shows  the  successive  part's  of  a  single  crystal,  as  dissected  by  B.  Horsford 


*  Die  Krystalliten  von  Hermann  Vogelsang.     Bonn,  1875. 


CRYSTALLINE   AGGREGATES.  Ill 

of  Springfield,  Mass. ;  371,  one  of  the  four  white  portions ;  and  372,  the 
central  black  portion. 


LITERATURE. 

Some  of  the  most  important  works  on  the  subject  are  referred  to  here,  but  for  a  complete 
list  of  the  literature  up  to  1873,  reference  may  be  made  to  Ilosenbusch  (see  below). 

Blum,  Leonhard,  Seyfert,  and  Sochting,  die  Einschliisse  von  Mineralien  in  krystallisirten 
Mineralien.  (Preisschrif  t. )  Haarlem,  1854. 

Bretoster.  Many  papers  published  mostly  in  the  Philosophical  Magazine,  and  the  Edinburgh 
Phil.  Journal,  from  1822-1856. 

Fischer.  Kritische-microscopische  mineralogische  Studien.  Freiburg  in  Br.,  64  pp. ,  1869 ; 
Ite  Fortsetzung,  64  pp.,  1871  ;  2te  Forts.,  90  pp.,  1878. 

Kosmann.  Ueber  das  Schillern  und  den  Dichroismus  des  Hypersthens.  Jahrb.  Min. ,  1869, 
368  (ibid.  p.  532,  1871,  p.  501). 

RosenbuscJi.  Microscopische  Physiographic  der  petrographisch  wichtigen  Mineralien. 
395  pp.,  Leipzig,.  1873. 

Schrauf.    Studien  an  der  Mineralspecies  Labradorit.     Ber.  Ak.  Wien,  lx.,  Dec.,  1869. 

Sorby.  On  the  microscopical  structure  of  crystals,  indicating  the  origin  of  minerals  and 
rocks. '  Q.  J.  Geol.  Soc.,  xiv.,  453,  1858,  (and  many  other  papers). 

Sorby  and  Butler.  On  the  structure  of  rubies,  sapphires,  diamonds,  and  some  other  minerals. 
Proc.  Roy.  Soc.,  No.  109,  1869. 

Vogelsang.    Die  Krystalliten.     175  pp.,  Bonn,  1875. 

Vogelsang  and  G-eissler.  Ueber  die  Natur  der  Flussigkeitseinschliisse  in  gewissen  Minera- 
lien. Pogg.  Ann.,  cxxxvii.,  56,  1869  (ibid.  p.  257).  _ 

Zirkel  Die  microscopische  Beschaff  enheit  der  Mineralien  und  G-esteine.  502  pp. ,  Leipzig, 
1873. 

CRYSTALLINE  AGGREGATES. 

The  greater  part  of  the  specimens  or  masses  of  minerals  that  occur,  may 
be  described  as  aggregations  of  imperfect  crystals.  Even  those  whose 
structure  appears  the  most  purely  impalpable,  and  the  most  destitute  in- 
ternally of  anything  like  crystallization,  are  probably  composed  of  crystal- 
line grains.  Under  the  above  head,  consequently,  are  included  all  the 
remaining  varieties  of  structure  in  the  mineral  kingdom. 

The  individuals  composing  imperfectly  crystallized  individuals,  may  be: 

1.  Columns,  or  fibres^  in  which  case  the  structure  is  columnar. 

2.  Thin  lamina,  producing  a  lamellar  structure. 

3.  Grains,  constituting  a  granular  structure. 

1.   Columnar  Structure. 

A  mineral  possesses  a  columnar  structure  when  it  is  made  up  of  slender 
columns  or  fibres.  There  are  the  following  varieties  of  the  columnar  struc- 
ture : 

Fibrous  :  when  the  columns  or  fibres  are  parallel.  Ex.  gypsum,  asbestus. 
Fibrous  minerals  have  often  a  silky  lustre. 


112  CRYSTALLOGRAPHY. 

Reticulated :  when  the  fibres  or  columns  cross  in  various  directions,  and 
produce  an  appearance  having  some  resemblance  to  a  net. 

Stellated  or  stellular :  when  they  radiate  from  a  centre  in  all  directions, 
and  produce  star-like  forms.  Ex.  stilbite,  wavellite. 

Radiated,  divergent :  when  the  crystals  radiate  from  a  centre,  without 
producing  stellar  forms.  Ex.  quartz,  stibnite. 


2.  Lamellar  Structure. 

The  structure  of  a  mineral  is  lamellar  when  it  consists  of  plates  or 
leaves.  The  laminae  may  be  curved  or  straight,  and  thus  give  rise  to  the 
curved  lamellar,  and  straight  lamellar  structure.  Ex.  wollastonite  (tabular 
spar),  some  varieties  of  gypsum,  talc,  etc.  When  the  laminse  are  thin  and 
easily  separable,  the  structure  is  said  to  be  foliaceous.  Mica  is  a  striking 
example,  and  the  term  micaceous  is  often  used  to  describe  this  kind  of 
structure. 

3.  Granular  Structure. 

The  particles  in  a  granular  structure  differ  much  in  size.  When  coarse, 
the  mineral  is  described  as  coarsely  granular  /  when  fine,  finely  granular; 
and  if  not  distinguishable  by  the  naked  eye,  the  structure  is  termed  im- 
palpable. Examples  of  the  first  may  be  observed  in  granular  crystalline 
limestone,  sometimes  called  saccharoidal ;  of  the  second,  in  some  varieties 
of  hematite  ;  of  the  last,  in  chalcedony,  opal,  and  other  species. 

The  above  terms  are  indefinite,  but  from  necessity,  as  there  is  every 
degree  of  fineness  of  structure  in  the  mineral  species,  from  perfectly  im- 
palpable, through  all  possible  shades,  to  the  coarsest  granular.  The  term 
phanero-crystalline  has  been  used  for  varieties  in  which  the  grains  are  dis- 
tinct, and  crypto-crystalline,  for  those  in  which  they  are  not  discernible. 

Granular  minerals,  when  easily  crumbled  in  the  fingers,  are  said  to  be 
friable. 

4.  Imitative  Shapes. 

Reniform  :  kidney  shape.     The  structure  may  be  radiating  or  concentric. 

Botryoidal:  consisting  of  a  group  of  rounded  prominences.  The  name 
is  derived  from  the  Greek  fiorpvs,  a  bunch  of  grapes.  Ex.  limonite,  chal- 
cedony. 

Mammillary :  resembling  the  botryoidal,  but  composed  of  larger  prom- 
inences. 

Globular  :  spherical  or  nearly  so  ;  the  globules  may  consist  of  radiating 
fibres  or  concentric  coats.  When  attached,  as  they  usually  are,  to  the  sur- 
face of  a  rock,  they  are  described  as  implanted  globules. 

Modular  :  in  tuberose  forms,  or  having  irregular  protuberances  over  the 
surface. 

Amygdaloidal :  almond-shaped,  applied  usually  to  a  greenstone  contain- 
ing almond-shaped  or  sub-globular  nodules. 


PSEUDOMORPHOUS  CRYSTALS.  113 

Coralloidal :  like  coral,  or  consisting  of  interlaced  flexuous  branchings 
of  a  white  color,  as  in  some  aragonite. 

Dendritic  :  branching  tree-like. 

Mossy  :  like  moss  in  form  or  appearance. 

Filiform  or  Capillary :  very  slender  and  long,  like  a  thread  or  hair  ; 
consists  ordinarily  of  a  succession  of  minute  crystals. 

Acicular :  slender  and  rigid  like  a  needle. 

Reticulated :  net-like. 

Drusy :  closely  covered  with  minute  implanted  crystals. 

Stalactitic :  when  the  mineral  occurs  in  pendant  columns,  cylinders,  or 
elongated  cones. 

Stalactites  are  produced  by  the  percolation  of  water,  holding  mineral 
matter  in  solution,  through  the  rocky  roofs  of  caverns.  The  evaporation 
of  the  water  produces  a  deposit  of  the  mineral  matter,  and  gradually  forms 
a  long  pendant  cylinder  or  cone.  The  internal  structure  may  be  imper- 
fectly crystalline  and  granular,  or  may  consist  of  fibres  radiating  from  the 
central  column,  or  there  may  be  a  broad  cross-cleavage. 

Common  stalactites  consist  of  calcium  carbonate.  Chalcedony,  gibbsite, 
brown  iron  ore,  and  many  other  species,  also  present  stalactitic  forms. 

The  term  amorphous  is  used  when  a  mineral  has  not  only  no  crystalline 
form  or  imitative  shape,  but  also  does  not  polarize  the  light  even  in  its  minute 
particles,  and  thus  appears  to  be  destitute  wholly  of  a  crystalline  structure 
internally,  as  most  opal.  Such  a  structure  is  also  called  colloid  or  jelly- 
like,  from  the  Greek  for  glue.  Whether  there  is  a  total  absence  of  crystal- 
line structure  in  the  molecules  is  a  debated  point.  The  word  is  from  a, 
primitive,  and  pbpfyiri,  shape. 


PSEUDOMORPHOUS   CRYSTALS. 

Every  true  mineral  species  has,  when  crystallized,  a  form  peculiar  to 
itself ;  occasionally,  however,  crystals  are  found  that  have  the  form,  both 
as  to  angles  and  general  habit,  of  a  certain  species,  and  yet  differ  from  it 
entirely  in  chemical  composition.  Moreover  it  is  often  seen  that,  though 
in  outward  form  complete  crystals,  in  internal  structure  they  are  granular, 
or  waxy,  and  have  no  regular  cleavage. 

Such  crystals  are  called  pseudomorphs,  and  their  existence  is  explained 
by  the  assumption,  often  admitting  of  direct  proof,  that  the  original  min- 
eral has  been  changed  into  the  new  compound,  or  has  disappeared  through 
some  agency,  and  its  place  been  taken  by  another  chemical  compound  "to 
which  the  form  does  not  belong. 

Pseudomorphs  have  been  classed  under  several  heads. 

1.  Pseudomorphs  by  substitution. 

2.  Pseudomorphs  by  simple  deposition,  (a)  incrustation  or  (b)  infiltra- 
tion. 

3.  Pseudomorphs  by  alteration  •  and  these  may  be  altered 

(a)  without  a  change  of  composition,  by  paramorphism  ; 

(b)  by  the  loss  of  an  ingredient ; 

(c)  by  the  assumption  of  a  foreign  substance ; 

(d)  by  a  partial  exchange  of  constituents. 

8 


114  CRYSTALLOGRAPHY. 

1.  The  first  class  of  pseudomorplis,  by  substitution,  embrace  those  cases 
where  there  has  been  a  gradual  removal  of  the  original   material  and  a 
corresponding  and  simultaneous  replacement  of  it  by  another,  without, 
however,  any  chemical  reaction  between  the  two.     A  common  example  of 
this  is  a  piece  of  fossilized  wood,  where  the  original  fibre  has  been  replaced 
entirely  by  silica.     The  first  step  in  the  process  was  the  filling  of  all  the 
pores  and  cavities  by  the  silica  in  solution,  and  then  as  the  woody  fibre  by 
gradual  decomposition  disappeared,  the  silica  further  took  its  place.    Other 
examples  are  quartz  after  fluorite,  calcite,  and  many  other  species,  cassiterite 
after  orthoclase,  etc. 

2.  Pseudomorplis   by  incrustation,  form  a  less  important  class.     Such 
are  the  crusts  of  quartz  formed  over  fluorite.     In  most  cases  the  removal 
of  the  original  mineral  has  gone  on  simultaneously  with  the  deposit  of  the 
second,  so  that  the  resulting  pseudomorpb  is  properly  one  of  substitution. 
In  pseudomorplis  by  infiltration,  a  cavity  made  by  the  removal  of  a  crystal 
has  been  filled  by  another  mineral. 

3.  The  third  class  of  pseudomorphs,  by  alteration,  include  a  considerable 
proportion  of  the  observed  cases,  of  which  the  number  is  very  large.     Con- 
clusive evidence  of  the  change  which  has  gone  on  is  often  furnished  by  a 
kernel  of  the  original  mineral  in  the  centre  of  the  altered  crystal ;  e.g.,  a 
kernel  of  cuprite  in  a  pseudomorphous  octahedron  of  malachite  ;  also  of 
chrysolite  in  a  pseudomorphous  crystal  of  serpentine ;    of   corundum    in 
fibrolite,  or  spinel  (Genth). 

(a)  An  example  of  pararnorphism  is  furnished  by  the  change  of  aragonite 
to  calcite  at  a  certain  temperature  ;  also  the  paramorplis  of  rutile  after 
arkansite  from  Magnet  Cove. 

(b)  An  example  of  the  pseudomorphs  in  which  alteration  is  accompanied 
by  a  loss  of  ingredients  is  furnished  by  crystals  of  limonite  in  the  form  of 
siderite,  the  carbonic  acid   having  been  removed  ;    so  also  calcite  after 
gay-lussite  ;  native  copper  after  cuprite. 

(c)  In  the  change  of  cuprite  to  malachite,  e.g.,  the  familiar  crystals  from 
Chessy,  France,  an  instance  is  afforded  of  the  assumption  of  an  ingredient, 
viz.,  carbonic  acid.     Pseudomorphs  of  gypsum  after  anhydrite  occur,  where 
there  has  been  an  assumption  of  water. 

(d)  A  partial  exchange  of  constituents,  in  other  words,  a  loss  of  one  and 
gain  of  another,  takes  place  in  the  change  of  feldspar  to  kaolin,  in  which 
the  potash  silicate  disappears  and  water  is  taken   up  ;  pseudomorphs  of 
chlorite  after  garnet,  pyromorphite  after  galenite,  are  other  examples. 

The  chemical  processes  involved  in  such  changes  open  a  wide  field  for 
investigation,  in  which  Bischof,  Delesse  and  others  have  done  much. 


SECTION  II. 
PHYSICAL    CHAEAOTERS    OF    MINERALS. 

THE  physical  characters  of  minerals  are  those  which  relate :  I.,  to 
Cohesion  and  Elasticity,  that  is:  cleavage  and  fracture,  hardness,  and  ten- 
acity;  II.,  to  the  Mass  and  Volume,  the  specific  gravity  ;  III.,  to  Light, 
the  optical  properties  of  crystals ;  also  color,  lustre,  etc. ;  IV.,  to  Heat ; 
Y.,  to  Electricity  and  Magnetism ;  VL,  to  the  action  on  the  Senses,  as 
taste,  feel,  etc. 

I.  COHESION  AND  ELASTICITY. 

.By  cohesion  is  understood  the  resistance  which  any  body  makes  to  an 
extraneous  force  tending  to  separate  its  particles,  either  by  breaking  or 
scratching.  This  principle  leads  to  some  of  the  most  universally  important 
physical  characters  of  minerals, — cleavage,  fracture,  and  hardness. 

Elasticity,  on  the  other  hand,  is  the  force  which  tends  to  bring  the 
molecules  of  a  body  back  into  their  original  position,  from  which  they  have 
been  disturbed.  Upon  elasticity  depends,  for  the  most  part,  the  degree 
of  tenacity  possessed  by  different  minerals. 

A.  CLEAVAGE  AND  FRACTURE. 

1.  Cleavage.  —  Most  crystallized  minerals  have  certain  directions  in 
which  their  cohesive  power  is  weakest,  and  in  which  they  consequently 
yield  most  readily  to  an  exterior  force.  This  tendency  to  break  in  the 
direction  of  certain  planes  is  called  cleavage,  and  being  most  intimately 
connected  with  the  crystalline  form  it  has  already  been  necessary  to  define 
it,  and  to  mention  some  of  its  most  important  features  (p.  2).  Cleavage 
differs  (a)  according  to  the  ease  with  which  it  is  obtained,  and  (b)  accord- 
ing to  its  direction,  crystallographically  determined. 

(a)  Cleavage  is  c&\ie&  perfect  or  eminent  when  it  is  obtained  with  great 
ease,  affording  smooth,  lustrous  surfaces,  as  in  mica,  topaz,  calcite.     Inferior 
degrees  of  cleavage  are  spoken  of  as  distinct,  indistinct  or  imperfect,  inter- 
rupted, in  traces,  difficult.     These  terms  are  sufficiently  intelligible  without 
further  explanation.     It  may  be  noticed  that  the  cleavage  of  a  species  is 
sometimes  better  developed  in  some  of  its  varieties  than  in  others. 

(b)  Cleavage  is  also  named  according  to  the  direction,  crystallographically 
defined,  which  it  takes  in  a  species.     When  parallel  to  the  basal  section  (O) 
it  is  called  basal,  as  in  topaz ;  parallel  to  the  prism,  as  in  amphibole,  it  is 
called  prismatic  /  also  macrodiagonal,  orthodiagonal,  etc.,  when  parallel 
to  the  several  diametral  sections ;  parallel  to  the  faces  of  the  cube,  octa- 


116  PHYSICAL    CHARACTERS    OF   MINERALS. 

Ledron,  dodecahedron,  or  rhombohedron,  it  is  called  cubic,  as  galenite ; 
octahedral,  as  fluorite ;  dodecahedral,  as  sphalerite ;  rhombohedral,  as 
calcite. 

Intimately  connected  with  the  cleavage  of  crystallized  minerals  are  the  divisional  planes  in- 
vestigated by  Reusch  (see  Literature,  p.  1 18).  He  has  found  that  by  pressure,  or  by  a  sudden 
blow,  divisional  planes  are  in  many  cases  produced  which  are  analogous  to  the  cleavage 
planes.  The  first  he  calls  Gleitflachen,  or  planes  in  which  a  sliding  of  the  molecules  upon 
each  other  takes  place.  Thus,  for  example,  if  two  opposite  dodecahedral  edges  of  a  cubic 
cleavage  mass  of  rock-salt  are  regularly  filed  away,  and  the  mass  then  subjected  to  pressure 
in  this  direction,  a  Gl&itflache  is  obtained  parallel  to  the  dodecahedral  face. 

The  figures,  on  the  other  hand,  obtained  by  a  blow  on  a  rounded  steel  point,  placed  perpen- 
dicular to  the  natural  or  cleavage  face  of  a  crystal,  are  called  by  him.  fracture-figures  (Schlag- 
fi^uren).  The  divisional-planes  in  this  case  appear  as  cracks  diverging  from  the  point  where 
the  blow  has  been  made.  For  instance,  on  a  cubic  face  of  rock-salt  two  planes,  forming  a 
rectangular  cross,  are  obtained  ;  on  biaxial  mica,  a  six-rayed  (sometimes  three-rayed)  star 
results  from  the  blow,  one  ray  of  which  is  always  parallel  to  the  brachy diagonal  axis  of  the 
prism. 

2.  Fracture. — The  term  fracture  is  used  to  define  the  form  or  kind  of 
surface  obtained  by  breaking  in  a  direction  other  than  that  of  the  cleavage 
in  crystallized  minerals,  and  in  any  direction  in  massive  minerals.  When 
the  cleavage  is  highly  perfect  in  several  directions,  as  the  cubic  cleavage  of 
galenite,  fracture  is  often  not  readily  obtainable. 

Fracture  is  defined  as  : 

(a)  Conchoidal ;  when  a  mineral  breaks  with  curved  concavities,  more 
or  less  deep.     It  is  so  called  from  the  resemblance  of  the  concavity  to  the 
valve  of  a  shell,  from  concha,  a  shell /  flint. 

(b)  Even  •  when  the  surface  of  fracture,  though  rough,  with  numerous 
small  elevations  and  depressions,  still  approximates  to  a  plane  surface. 

(c)  Uneven  ;  when  the  surface  is  rough  and  entirely  irregular. 

(d)  Hackley  ;  when  the  elevations  are  sharp  or  jagged  ;  broken  iron. 
Other  terms  also  employed  are  earthy,  splintery,  etc. 


B.  HARDNESS. 

By  the  hardness  of  a  mineral  is  understood  the  resistance  which  it  offers 
to  abrasion.  The  degree  of  hardness  is  determined  by  observing  the  ease 
or  difficulty  with  which  one  mineral  is  scratched  by  another,  or  by  a  file  or 
knife. 

In  minerals  there  are  all  grades  of  hardness,  from  that  of  a  substance 
impressible  by  the  finger-nail  to  that  of  the  diamond.  To  give  precision 
to  the  use  of  this  character,  a  scale  of  hardness  was  introduced  by  MOHS. 
It  is  as  follows : 

1.  Talc;  common  laminated  light-green  variety. 

2.  Gypsum  /  a  crystallized  variety. 

3.  Calcite /  transparent  variety. 

4.  Fluorite  /  crystalline  variety. 

5.  Apatite ;  transparent  variety. 
(5.5.  Scapolite ;  crystalline  variety.) 

6.  Feldspar  (orthoclase) ;  white  cleavable  variety. 

7.  Quartz;  transparent. 


HARDNESS TENACITY.  117 

8.  Topaz  •  transparent. 

9.  8&pphvre:  cleavable  varieties. 
10.  Diamond. 

If  the  mineral  under  trial  is  scratched  by  the  file  or  knife  as  easily  as 
apatite,  its  hardness  is  called  5  ;  if  a  little  more  easily  than  apatite  and 
not  so  readily  as  fluorite,  its  hardness  is  called  4.5,  etc.  For  minerals  as 
hard  or  harder  than  quartz,  the  file  will  not  answer,  and  the  relative  hard- 
ness is  determined  by  finding  by  experiment  whether  the  given  mineral  will 
scratch,  or  can  be  scratched  by,  the  successive  minerals  in  the  scale. 

It  need  hardly  be  added  that  great  accuracy  is  not  attainable  by  the  above 
methods,  though,  indeed,  for  all  mineralogicai  purposes  exactness  is  quite 
unnecessary. 

The  interval  between  2  and  3,  and  5  and  6,  in  the  scale  of  Mohs,  being 
a  little  greater  than  between  the  other  numbers,  Breithaupt  proposed  a 
scale  of  twelve  minerals  ;  but  the  scale  of  Mohs  is  now  universally  accepted. 

Accurate  determinations  of  the  hardness  of  minerals  have  been  made  by 
Frankenheim,  Franz,  Grailich  and  Pek&rek,  and  others  (see  Literature, 
p.  118),  with  an  instrument  called  a  sclerometer.  The  mineral  is  placed  on 
a  movable  carriage  with  the  surface  to  be  experimented  upon  horizontal ; 
this  is  brought  in  contact  with  a  steel  point  (or  diamond-point),  fixed  on  a 
support  above;  the  weight  is  then  determined  which  is  just  sufiicient  to 
move  the  carriage  and  produce  a  scratch  on  the  surface  of  the  mineral. 

By  means  of  such  an  instrument  the  hardness  of  the  different  faces  of  a 
given  crystal  has  been  determined  in  a  variety  of  cases.  It  has  been  found 
that  different  planes  of  a  crystal  differ  in  hardness,  and  the  same  plane  dif- 
fers as  it  is  scratched  in  different  directions.  In  general,  the  hardest  plane 
is  that  which  is  intersected  by  the  plane  of  most  complete  cleavage.  And 
of  a  single  plane,  which  is  intersected  by  cleavage  planes,  the  direction 
perpendicular  to  the  cleavage  direction  is  the  softer,  those  parallel  to  it  the 
harder. 

This  subject  has  been  recently  investigated  by  Exner  (p.  118),  who  has  given  the  form  of 
the  curves  of  hardness  for  the  different  planes  of  many  crystals.  These  curves  are  obtained  as 
follows :  the  least  weight  required  to  scratch  a  crystalline  surface  in  different  directions, 
for  each  10°  or  15°,  from  0°  to  18(i°,  is  determined  with  the  sclerometer ;  these  directions 
are  laid  off  as  radii  from  a  centre,  and  the  length  of  each  is  made  proportional  to  the.  weight 
fixed  by  experiment,  that  is,  to  the  hardness  thus  determined  ;  the  line  connecting  the 
extremities  of  these  radii  is  the  curve  of  hardness  for  the  given  plane. 


C.  TENACITY. 

Solid  minerals  may  be  either  brittle,  sectile,  malleable,  flexible,  or  elastic. 

(a)  Brittle ;  when  parts  of  a  mineral  separate  in  powder  or  grains  on 
attempting  to  cut  it ;  calcite. 

(b)  Sectile  /  when  pieces  may  be  cut  off  with  a  knife  without  falling  to 
powder,  but  still  the  mineral  pulverizes  under  a  hammer.     This  character 
is  intermediate  between  brittle  and  malleable  ;  gypsum. 

(c)  Malleable  ;  when  slices  may  be  cut  off,  and  these  slices  flattened  out 
under  a  hammer;  native  gold,  native  silver. 

(d)  Flexible ;  when  the  mineral  will  bend,  and  remain  bent  after  the 
bending  force  is  removed ;  talc. 


118  PHYSICAL    CHARACTERS    OF   MINERALS. 

(e)  Elastic  /  when  after  being  bent,  it  will  spring  back  to  its  original 
position  ;  mica. 

The  elasticity  of  crystallized  minerals  is  a  subject  of  theoretical  rather 
than  practical  importance.  The  subject  has  been  acoustically  investigated 
by  Savart  with  very  interesting  results.  Reference  may  also  be  made  to 
the  investigations  of  Neumann,  and  later  those  of  Yoigt  and  Grotli.  The 
most  important  principle  established  by  these  researches  is,  as  stated  by 
Groth,  that  in  crystals  the  elasticity  (coefficient  of  elasticity)  differs  in 
different  directions,  but  is  the  same  in  all  directions  which  are  crystallo- 
graphically  identical ;  hence  he  gives  as  the  definition  of  a  crystal,  a  solid 
in  which  the  elasticity  is  a  function  of  the  direction. 

Intimately  connected  with  the  general  subjects  here  considered,  of  cohesion  in  relation 
to  minerals,  are  the  figures  produced  by  etching  on  crystalline  faces  (Aetzfiguren,  Germ.), 
investigated  by  Leydolt,  and  later  by  Baumhauer,  Exner,  and  others.  This  method  of  investi- 
gation is  of  high  importance  as  revealing  the  molecular  structure  of  thw  crystal ;  reference, 
however,  must  be  made  to  the  original  memoirs,  whose  titles  are  given  below,  for  the  full 
discussion  of  the  subject. 

The  etching  is  performed  mostly  by  solvents,  as  water  in  some  oases,  more  generally  the 
ordinary  mineral  acids,  or  caustic  alkalies,  also  by  steam  and  hydrofluoric  acid ;  the  latter  is 
especially  powerful  in  its  action.  The  figures  produced  are  in  the  majority  of  cases  angular 
depressions,  such  as  low  triangular,  or  quadrilateral  pyramids,  whose  outlines  run  parallel  to 
some  of  the  crystalline  edges.  In  some  cases  the  planes  produced  can  be  referred  to  occur- 
ring crystallographic  planes.  They  appear  alike  on  similar  planes  of  crystals,  and  hence 
serve  to  distinguish  different  forms,  perhaps  in  appearance  identical,  as  the  two  sets  of  planes 
in  the  ordinary  double  pyramid  of  quartz  ;  so,  too,  they  reveal  the  compound  twinning  struc- 
ture common  on  some  crystals,  as  quartz  (p.  89)  and  aragonite. 

Analogous  to  the  etching-figures  are  the  figures  produced  on  the  faces  of  some  crystals  by 
the  loss  of  water  (Verwitterungsfiguren,  Germ.)  This  subject  has  been  investigated  by  Pape 
(see  below). 

LITERATURE. 
Cohesion  ;   Hardness. 

Frankenheim.  De  Crystallorum  Cohaesione,  1829  ;  also  in  Baumgarfcner's  Zeitschrift  fur 
Physik,  ix.,  94,  194.  1831. 

Frankenheim.    Ueber  die  Anordnung  der  Molecule  in  Krystallen  ;  Pogg.  xcvii.,  337.  1856. 

Sohnpke.  Ueber  die  Cohasion  des  Steinsalzes  in  krystallographisch  verschiedenen  Rich- 
tungen;  Pogg.  cxxxvii.,  177.  1869. 

Franz.  Ueber  die  Harte  der  Mineralien  und  ein  neues  Verfahren  dieselbe  zu  messen ; 
Pogg.  Ixxx.,  37.  1850. 

Grailich  und  Pekdrek.    Ber.  Ak.  Wien,  xiii.,  410.  1854. 

Exner.    Ueber  die  Harte  der  Krystallflachen ;  166  pp.     Wien,  1873. 


Elasticity. 

Savart.    Pogg.  Ann.,  xvi.,  306. 

Neumann.    Pogg.  Ann.,  xxxi.,  177. 

Voigt.    Pogg.  Ann.  Erg.  Bd.,  vii,  i,  177,  1875. 

(froth.    Pogg.  Ann.,  cl vii.,  115,  787.    1876. 

Bauer.  Untersuchung  iiber  den  Glimmer  und  verwandte  Minerale  ;  Pogg.  cxxxviii.,  337, 
1869. 

Reusch.  Ueber  die  Kornerprobe  am  Steinsalz  u.  Kalkspath.  Pogg.  cxxxil,  441,  1867; — 
am  zwei-axigen  Glimmer,  Pogg.  Ann.  cxxxvi,  430,  632  ; — am  krystallirten  Gyps,  ibid.,  p.  135. 


SPECIFIC    GRAVITY.  119 

Baumhauer.  Ueber  Aetzfiguren  und  die  Erscheinungen  dea  Asterismus  an  Krystallen  ; 
Pogg.  Ann.  cxxxviii.,  163  ;  cxxxix.,  349  ;  cxL,  271  ;  cxlv.,  459  ;  cliii.,  621 ;  Ber.  Ak.  Mimchen, 
1875,  169. 

Danied.    Quarterly  Journal  of  Science,,  i.,  24.    1816. 

Exner.    An  Losungsfiguren  in  Krystallen;   Ber.  Ak.  Wien,  Ixix.,  6.    1874. 

Hirsehwald.    Aetzfiguren  an  Quarz- Krystallen ;   Pogg.  cxxxvii. ,  548.    1869. 

Knop.    Jahrb.  Min.,  1872,  785. 

Leydolt.     Ueber  Aetzungen ;  Ber.  Ak.  Wien,  xv.,  58;  xix.,  10. 

Pape.  Ueber  das  Verwitterungs-Ellipsoid  wasserhaltiger  Krystalle ;  Pogg.  cxxiv.,  329; 
cxxv.,  513.  1865. 


II.  SPECIFIC  GKAVITY. 

The  specific  gravity  of  a  mineral  is  its  weight  compared  with  that  of  an- 
other substance  of  equal  volume,  whose  gravity  is  taken  at  unity.  In  the 
case  of  solids  or  liquids,  this  comparison  is  usually  made  with  water.  If  a 
cubic  inch  of  any  mineral  weighs  twice  as  much  as  a  cubic  inch  of  water 
(water  being  the  unit),  its  specific  gravity  is  2,  if  three  times  as  much,  its 
specific  gravity  is  3,  etc. 

The  direct  comparison  by  weight  of  a  certain  volume  of  water  with  an 
equal  volume  of  a  given  solid  is  not  often  practicable.  By  making  use, 
however,  of  a  familiar  principle  in  hydrostatics,  viz.,  that  the  weight  lost 
by  a  solid  immersed  in  water  is  equal  to  the  weight  of  an  equal  volume  of 
water,  that  is  of  the  volume  of  water  it  displaces, — the  determination  of  the 
specific  gravity  becomes  a  very  simple  process. 

The  weight  of  the  solid  out  of  water  (w)  is  determined  by  weighing  in 
the  usual  manner ;  then  the  weight  in  water  is  found  (w')9  when  the  loss  by 
immersion  or  the  difference  of  the  two  weights  (w  —  w')  is  the  weight  of  a 
volume  of  water  equal  to  that  of  the  solid  ;  finally  the  quotient  of  the  first 
weight  (w)  by  that  of  the  equal  volume  of  water  as  determined  (w  —  w') 
is  the  specific  gravity  (G). 

Hence, 

For  example,  the  weight  of  a  fragment  of  quartz  is  found  to  be  4.534 
grams.  Its  weight  in  water  =  2.817  grains,  and  therefore  the  loss  of 
weight,  or  the  weight  of  an  equal  volume  of  water  =  1.717.  Consequently 

4  534 
the  specific  gravity  is  equal  to     '       ,  or  2.641. 

The  ordinary  method  for  obtaining  the  specific  gravity  of  firm,  solid 
minerals  is  first  to  weigh  the  specimen  accurately  on  a  good  chemical  bal- 
ance, then  suspend  it  from  one  pan  of  the  balance  by  a  horse-hair,  silk 
thread,  or  better  still  by  a  fine  platinum  wire,  in  a  glass  of  water  con- 
veniently placed  beneath.  The  platinum  wire  may  be  wound  around  the 
specimen,  or  where  the  latter  is  small  it  may  be  made  at  one  end  into  a 
little  spiral  support.  While  thus  suspended,  the  weight  is  again  taken  with 
the  same  care  as  before. 

The  water  employed  for  this  purpose  should  be  distilled,  to  free  it  from 
all  foreign  substances.  Since  the  density  of  water  varies  with  its  tempera- 
ture, a  particular  temperature  has  to  be  selected  for  these  experiments,  in 


120  PHYSICAL    CHARACTERS    OF   MINERALS. 

order  to  obtain  uniform  results:  60°  F.  is  the  most  convenient,  and  has 
been  generally  adopted.  But  the  temperature  of  the  maximum  density  of 
water,  39.5°  F.  (4°  0.),  has  been  recommended  as  preferable.  For  minerals 
soluble  in  water  some  other  liquid,  as  alcohol,  benzene,  etc.,  must  be  em- 
ployed, whose  specific  gravity  (g)  is  accurately  known  ;  from  the  com- 
parison with  it,  the  specific  gravity  (G)  of  the  mineral  as  referred  to  water 
is  determined,  as  by  the  formula  : 


w 


w  —  w 


A  very  convenient  form  of  balance  is  the  spiral  balance  of  Jolly,  where  the  weight  is  mea- 
sured by  the  torsion  of  a  spiral  brass  wire.  The  readings,  which  give  the  weight  of  the  min- 
eral in  and  out  of  water,  are  obtained  by  observing  the  coincidence  of  the  index  with  its 
image  reflected  in  the  mirror  on  which  the  graduation  is  made. 

A  form  of  balance  m  which  weights  are  also  dispensed  with,  the  specific  gravity  being  read 
off  from  a  scale  without  calculation,  has  recently  been  described  by  Parish  (Am.  J.  Sci.,  III., 
x.,  352).  Where  great  accuracy  is  not  required,  it  can  be  very  conveniently  used. 

If  the  mineral  is  not  solid,  but  pulverulent  or  porous,  it  is  best  to  reduce 
it  to  a  powder  and  weigh  it  in  a  little  glass  bottle  (f.  373) 
called  a  pygnometer.  This  bottle  has  a  stopper  which 
fits  tightly  and  ends  in  a  tube  with  a  very  fine  opening. 
The  bottle  is  filled  with  distilled  water,  the  stopper  in- 
serted, and  the  overflowing  water  carefully  removed  with 
a  soft  cloth.  It  is  now  weighed,  and  also  the  mineral 
whose  density  is  to  be  determined.  The  stopper  is  then 
removed  and  the  mineral  in  powder  or  in  small  fragments 
inserted,  with  care,  so  as  not  to  introduce  air-bubbles. 
The  water  which  overflows  on  replacing  the  stopper  is 
the  amount  of  water  displaced  by  the  mineral.  The 
weight  of  the  pygnometer  with  the  enclosed  mineral  is 
determined,  and  the  weight  of  the  water  lost  is  obviously 
the  difference  between  this  last  weight  and  that  of  the 
bottle  and  mineral  together,  as  first  determined.  The  specific  gravity  of 
the  mineral  is  equal  to  its  weight  alone  divided  by  the  weight  of  the  equal 
volume  of  water  thus  determined. 

Where  this  method  is  followed  with  sufficient  care,  especially  avoiding 
any  change  of  temperature  in  the  water,  the  results  are  quite  accurate. 
Other  methods  of  determining  the  specific  gravity  will  be  found  described 
in  the  literature  notices  which  follow. 

It  has  been  shown  by  Rose  that  chemical  precipitates  have  uniformly  a 
higher  density  than  belongs  to  the  same  substance  in  a  less  finely  divided 
state.  This  increase  of  density  also  characterizes,  though  to  a  less  extent, 
a  mineral  in  a  fine  state  of  mechanical  subdivision.  This  is  explained 
by  the  condensation  of  the  water  on  the  surface  of  the  powder. 

It  may  also  be  mentioned  that  the  density  of  many  substances  is  altered 
by  fusion.  The  same  mineral  in  different  states  of  molecular  aggregation 
may  differ  somewhat  in  density.  Furthermore,  minerals  having  the  same 
chemical  composition  have  sometimes  different  densities  corresponding  to  the 
different  crystalline  forms  in  which  they  appear  (see  p.  177). 


LIGHT.  121 

For  all  minerals  in  a  state  of  average  purity  the  specific  gravity  is  one  of 
the  most  important  and  constant  characteristics,  as  urged  especially  by 
Breithanpt.  Every  chemical  analysis  of  a  mineral  should  be  accompanied 
by  a  careful  determination  of  its  density. 

Practical  suggestions. — The  fragment  taken  should  not  be  too  large,  say  from  two  to  five 
grams  for  ordinary  cases,  varying  somewhat  with  the  density  of  the  mineral.  The  substance 
must  be  free  from  impurities,  internal  and  external,  and  not  porous.  Care  must  be  taken  to 
exclude  air-bubbles,  and  it  will  often  be  found  well  to  moisten  the  surface  of  the  specimen 
before  inserting  it  in  the  water,  and  sometimes  boiling  is  necessary  to  free  it  from  air.  If  it 
absorbs  water  this  latter  process  must  be  allowed  to  go  on  till  the  substance  is  fully  satu- 
rated. No  accurate  determinations  can  be  made  unless  the  changes  of  temperature  are 
rigorously  excluded  and  the  actual  temperature  noted. 

In  a  mechanical  mixture  of  two  constituents  in  known  proportions,  when  the  specific 
gravity  of  the  whole  and  of  one  are  known,  that  of  the  other  can  be  readily  obtained.  This 
method  is  often  important  in  the  study  of  rocks. 


LITERATURE. — SPECIFIC  GRAVITY. 

Beudant.    Pogg.  Ann.,  xiv.,  474.     1828. 

Jenzsch.     Ueber  die  Bestimmung  der  specifischen  Gewichte  ;  Pogg.  xcix.,  151.     1856. 

Jolly.    Ber.  Ak.  Miinchen,  1864,  162. 

Gadolin.  Eine  einfache  Methode  zur  Bestimmung  des  specifischen  Gewichtes  der  Minera- 
lien;  Pogg.,  cvi.,  213.  1859. 

G.  Rose.  Ueber  die  Fehler,  welche  in  der  Bestimmung  des  specifischen  Gewichtes  der 
Korper  entstehen,  wenn  man  dieselben  im  Zustande  der  feinsten  Vertheilung  wiigt ;  Pogg. 
Ixxiii.,  Ixxv  ,  403.  1848. 

ScJieerer.  Ueber  die  Bestimmung  des  specifischen  Gewichtes  von  Mineralien  ;  Pogg.  Ann. , 
Ixvii.,  120,  1846.  Journ.  pr.  Ch.,  xxiv.,  139. 

tichiff.    Ann.  Ch.  Pharm.,  cviii..  29.    1858. 

Schroder.    Neue  Beitriige  zur  Volumentheorie  ;  Pogg.  cvi.,  226.     1859. 

;  Die  Volumconstitution   einiger  Mineralien  ;  Jahrb.  Min.,  1873,   561,  932  ;  1874, 

399,  etc. 

Tschermak.    Ber.  Ak.  Wien,  292,  1863. 

Websky.  Die  Mineralien  nach  den  fur  das  specifische  Gewicht  derselben  angenommenen 
und  gefundenen  Werthen ;  170  pp.  Breslau,  1868. 


III.  LIGHT. 

Before  considering  the  distinguishing  optical  properties  of  crystals  of  the 
different  systems,  it  is  desirable  to  review  briefly  some  of  the  more  im- 
portant principles  of  '  optics  upon  which  the  phenomena  in  question 
depend. 

Nature  of  light. — In  accordance  with  the  undulatory  theory  of  Huy- 
ghens,  as  further  developed  by  Young  and  Fresnel,  light  is  conceived  to 
consist  in  the  vibrations,  transverse  to  the  direction  of  propagation,  of  the 
particles  of  imponderable,  elastic  ether,  which  it  is  assumed  pervades  all 
space  as  well  as  all  material  bodies.  These  vibrations  are  propagated  with 
great  velocity  in  straight  lines  and  in  all  directions  from  the  luminous 
point,  and  the  sensation  which  they  produce  on  the  nerves  of  the  eye  is 
called  light. 

The  nature  of  the  vibrations  will  be  understood  from  f.  374.  If  AB 
represents  the  direction  of  propagation  of  the  light-ray,  each  particle  of 
ether  vibrates  at  right  angles  to  this  as  a  line  of  equilibrium.  The  vibra- 


122  PHYSICAL    CHARACTERS    OF    MINERALS. 

tion  of  the  first  particle  induces  a  similar  movement  in  the  adjacent  par- 
ticle ;  this  is  communicated  to  the  next,  and  so  on.  The  particles  vibrate 
successively  from  the  line  AB  to  a  distance  corresponding  to  bb' ',  called  the 
amplitude  of  the  vibration,  then  return  to  b  and  pass  on  to  b",  and  so 

374 


on.  Thus  at  a  given  instant  there  are  particles  occupying  all  positions, 
from  that  of  the  extreme  distance  5',  or  0',  from  the  line  of  equilibrium  to 
that  on  this  line.  In  this  way  the  wave  of  vibration  moves  forward,  while 
the  motion  of  the  particles  is  only  transverse.  In  the  figure  the  vibrations 
are  represented  in  one  plane  only,  but  in  ordinary  light  they  take  place  in 
all  directions  about  the  line  AB.  The  distance  between  any  two  particles, 
which  are  in  like  positions,  of  like  phase,  as  V  and  c'.,  is  called  the  wave- 
length •  and  the  time  required  for  this  completed  movement  is  called  the 
time  of  vibration.  The  intensity  of  the  light  varies  with  the  amplitude  of 
the  vibrations,  and  the  color  depends  upon  the  length  of  the  waves ;  the 
wave-lengths  of  the  violet  rays  are  shorter  than  those  of  the  red  rays. 

Two  waves  of  like  phase,  propagated  in  the  same  direction  and  of  equal 
intensity,  on  meeting  unite  to  form  a  wave  of  double  intensity  (double 
amplitude).  If  the  waves  differ  in  phase  by  half  a  wave-length,  or  an  odd 
multiple  of  this,  they  interfere  and  extinguish  each  other.  For  other  rela- 
tions of  phase  they  are  also  said  to  interfere,  forming  a  new  resultant  wave, 
differing  in  phase  and  amplitude  from  each  of  the  component  waves ;  if 
they  are  waves  of  white  light,  their  interference  is  indicated  by  the  appear- 
ance of  the  successive  colors  of  the  spectrum.  The  propagation  of  the 
vibration -waves  of  light  is  sometimes  compared  to  the  effect  produced 
when  a  pebble  is  thrown  in  a  sheet  of  quiet  water — a  series  of  concentric 
circular  waves  are  sent  out  from  the  point  of  agitation.  These  waves  con- 
sist in  the  transverse  vibration  of  the  particles  of  water,  the  waves  move 
forward,  but  the  water  simply  vibrates  to  and  fro  vertically. 

The  waves  of  light  are  propagated  forward,  in  an  analogous  manner,  in 
all  directions  from  the  luminous  point,  and  the  surface  which  contains  all 
the  particles  which  commence  their  vibrations  simultaneously  is  called  the 
wave-surface  (Wellenflache,  Germ.). 

If  the  propagation  of  light  goes  on  with  the  same  velocity  in  all  direc- 
tions in  a  homogeneous  medium,  the  wave-surface  is  obviously  that  of  a 
sphere  and  the  medium  is  said  to  be  isotrope.  If  it  takes  place  with  dif- 
ferent velocities  in  different  directions  in  a  body,  the  wave-surface  is  some- 
times an  ellipsoid,  but  never  spherical,  as  is  shown  later;  such  a  body  is 
called  anisotrope. 

All  the  phenomena  of  optics  are  explained  upon  the  supposition  of  waves 
of  light,  whose  change  of  direction  accompanies  refraction,  whose  interfer- 
ence produces  the  colored  bands  of  the  diffraction  spectra,  etc.  For  the 
full  discussion  of  the  subject  reference  must  be  made  to  works  on  optics. 


RE  FRACTION    OF    LIGHT. 


123 


Refraction. — A  ray  of  light  passing  through  a  homogeneous  medium  is 
always  propagated  in  a  straight  line  without  deviation.  When,  however, 
the  light-ray  passes  from  one  medium  to  another,  which  is  of  different 
density,  it  suffers  a  change  of  direction,  which  is  called  refraction.  For  in- 
stance, in  f.  375,  if  ca  is  a  ray  of  light  passing  from  air  into  water,  its  path 
will  be  changed  after  passing  the  surface  at 
<&,  and  it  will  continue  in  the  direction  ab. 
Conversely,  if  a  ray  of  light,  ba,  pass  from 
the  denser  medium,  water,  into  the  rarer 
medium,  air,  at  a}  it  will  take  the  direction 
ac. 

If  now  mao  is  a  perpendicular  to  the  sur- 
face at  a,  it  will  be  seen  that  the  angle  cam, 
called  the  angle  of  incidence  (i)  of  the  ray 
ca  is  greater  than  the  angle  bao,  called  the 
angle  of  refraction  (/•),  and  what  is  observed 
in  this  case  is  found  to  be  universally  true, 
and  the  law  is  expressed  as  follows : 

A.  ray  of  light  in  passing  from  a  rarer 
to  a  denser  medium  is  refracted'  TOWARDS 
the  perpendicular  •  if  from  a  denser  to  a  rarer  medium  it  is  refracted 
AWAY  FROM  the  perpendicular. 

A  further  relation  has  also  been  established  by  experiment :  however 
great  or  small  the  angle  of  incidence,  cam  (?'),  may  be,  there  is  always  a 
constant  relation  between  it  and  the  angle  of  refraction,  gain  (r),  for  two 
given  substances,  as  here  for  air  and  water.  This  is  seen  in  the  figure  where 
af  and  da  are  the  sines  of  the  two  angles,  and  their  ratio  (=  ^  nearly)  is 
the  same  as  that  of  the  sine  of  any  other  angle  of  incidence  to  the  sine  of 
its  angle  of  refraction.  This  principle  is  expressed  as  follows : 

The  sine  of  the  angle  of  incidence  bears  a  constant  ratio  to  the  sine  of 
the  angle  of  refraction. 

This  constant  ratio  between  these  two  angles  is  called  the  index  of  refrac- 
tion, or  simply  n.  In  the  example  given  for  air  and  water  -  -,'=  1.335, 

and  consequently  the  value  of  the  index  of  refraction,  or  n,  is  1.335. 

The  following  table  includes  the  values  of  n  for  a  variety  of  substances. 
For  all  crystallized  minerals,  except  those  of  the  isometric  system,  the  index 
of  refraction  has  more  than  one  value,  as  is  explained  in  the  pages  which 
follow. 


Ice: 1.308 

Water 1.335 

Fluorite 1.436 

Alum 1.457 

Chalcedony 1.553 

Eock-salt 1.557 

Quartz 1.548 


Calcite 1.654 

Aragonite 1.693 

Boracite 1.701 

Garnet 1.815 

Zircon 1.961 

Blende 2.260 

Diamond..  2.419 


In  the  principle  which  has  been  stated,  - —  —  n.  two  points  are  to  be 

Sill/* 


124  PHYSICAL    CHARACTERS    OF   MINERALS. 

noted.  First,  if  the  angle  i  —  0°,  then  sin  i  •=.  0,  and  obviously  also  r  =  0, 
in  other  words,  when  the  ray  of  light  coincides  with  the  perpendicular  no 
refraction  takes  place,  the  ray  proceeding  onward  into  the  second  medium 
without  deviation. 

Again,  if  the  angle  i  =  90°,  then  sin  i  =  1,  and  the  equation  above  be- 

comes -  =  n*  or  sin  r  —  —  .     As  n  has  a  fixed  value  for  every  substance, 
sin  r  n 

it  is  obvious  that  there  will  also  be  a  corresponding  value  of  the  angle  r 
for  the  case  mentioned.  From  the  above  table  it  is  seen  that  for  water 

sin  r  ==  —^^z,  and  r  =  48°  35'  ;  for  diamond,  sin  r  =  —  -,  and  r  =  24°  25'. 


In  the  example  employed  above,  if  the  angle  bao  (r)  =  48°  35',  the  line  ac 
will  coincide  with  of,  supposing  the  light  to  go  from  b  to  a.  If  r  is  greater 
than  48°  35',  the  ray  no  longer  passes  from  the  water  into  the  air,  but  suffers 
total  reflection  at  the  surface  a.  This  value  of  r  is  said  to  be  the  limiting 
value  for  the  given  substance.  The  smaller  it  is  the  greater  the  amount  of 
light  reflected,  and  the  greater  the  apparent  'brilliancy  of  the  substance  in 
question.  This  is  the  explanation  of  the  brilliancy  of  the  diamond. 

Determination  of  the  index  of  refraction.  —  By  means  of  a  prism,  as 

MNP  in  f.  376,  it  is  possible  to  determine 
the  value  of  n,  or  index  of  refraction  of  a 
given  substance.  The  full  explanation  of 
this  subject  belongs  to  works  on  optics,  but 
a  word  is  devoted  to  it  here.  If  the  material 
is  solid,  a  prism  must  be  cut  and  polished, 
with  its  edge  in  the  proper  direction,  and 
having  not  too  small  an  angle.  If  the  refrac- 

**  p  tive  index  of  a  liquid  is  required,  it  is  placed 

within  a  hollow  prism,  with  sides  of  plates  of  glass  having  both  surfaces 
parallel. 

The  angle  of  the  prism,  MN  P  (a),  is,  in  each  case,  measured  in  the 
same  manner  as  the  angle  between  two  planes  of  a  crystal,  and  then  the 
"mattimum  amount  of  deviation  ($}  of  &  monochromatic  ray  of  light  passing 
from  a  slit  through  the  prism  is  also  determined.  The  amount  of  deviation 
of  a  ray  in  passing  through  the  prism  varies  with  its  position,  but  when  the 
prism  is  so  placed  that  the  ray  makes  equal  angles  with  the  sides  of  the 
prism  (i  =  i',  f.  376),  both  when  entering  and  emerging,  this  deviation  has 
a  fixed  minimum  value. 

If  8  =  the  minimum  deviation  of  the  ray,  and 

,  ,  -,      £  ^.          •        ^  sin  i(a  +  S) 

a  =  the  angle  or  the  prism,  then  n  =  -  :  —  --?-  —  -. 

sin-JS 

In  determining  the  value  of  n  for  different  colors,  it  is  desirable  to  employ 
rays  of  known  position  in  the  spectrum. 

Double  refraction.  —  Hitherto  the  existence  of  only  one  refracted  ray  has 
been  assumed  when  light  passes  from  one  medium  to  another.  But  it  is 
a  well-known  fact  that  there  are  sometimes  two  refracted  rays.  The  most 
familiar  example  of  this  is  furnished  by  the  mineral  calcite,  also  called  on 
account  of  this  property  u  doubly-refracting  spar." 

If  mnop  (f.  377)  be  a  cleavage  piece  of  calcite,  and  a  ray  of  light  meets 


REFLECTION,  DISPERSION   AND    DIFFRACTION   OF   LIGHT.  125 

it  at  &,  it  will,  in   passing    through,  be  divided    into    two  rays,  be,  bd. 
Similarly  a  line  seen   through  a  piece  of  calcite  ordi- 
narily appears  double. 

It  will  be  seen,  however,  that  the  same  property  is 
enjoyed  by  the  great  majority  of  crystallized  minerals, 
though  in  a  less  striking  degree. 

Reflection,. — When  a  ray  of  light  passes  from  one 
medium  to  another,  for  example,  from  air  to  a  denser 
substance,  as  has  been  illustrated,  the  light  will  be  par- 
tially transmitted  and  refracted  by  the  latter,  in  the 
manner  illustrated,  but  a  portion  of  it  (the  ray  ag,  in  f.  375),  is  always 
reflected  back  into  the  air.  The  direction  of  the  reflected  ray  is  known 
in  accordance  with  the  following  law : 

The  angles  of  incidence  and  reflection  are  equal. — In  f.  378  the  angle 
cam  is  equal  to  the  angle  mag. 

The  relative  amount  of  light  reflected  and  transmitted  depends  upon  the 
angle  of  incidence,  and  also  upon  the  transparency  of  the  second  medium. 
If  the  surface  of  the  latter  is  not  perfectly  polished,  diffuse  reflection  will 
take  place,  and  there  will  be  no  distinct  reflected  ray. 

Still  another  important  principle,  in  relation  to  the  same  subject,  remains 
to  be  enunciated  :  The  rays  of  incidence,  reflection,  and  refraction  all  lie 
in  the  same  plane. 

Dispersion. — Thus  far  the  change  in  direction  which  a  ray  of  light  suffers 
on  refraction  has  alone  been  considered.  It  is  also  true  that  the  amount 
of  refraction  differs  for  the  different  colors  of  which  ordinary  white  light 
is  composed,  being  greater  for  blue  than  for  red.  In  consequence  of  this 
fact,  if  a  ray  of  ordinary  light  pass  through  a  prism,  as  in  f.  376,  it  will 
not  only  be  refracted,  but  it  will  also  be  separated  into  its  component  colors, 
thus  forming  the  spectrum. 

This  variation  for  the  different  colors  depends  directly  upon  their  wave- 
lengths ;  the  red  rays  have  longer  waves,  and  vibrate  more  slowly,  and 
hence  suffer  less  refraction  than  the  violet  rays,  for  which  the  wave-lengths 
are  shorter  and  the  velocity  greater. 

Interference  of  light ;  diffraction. — When  a  ray  of  monochromatic  light 
is  made  to  pass  through  a  narrow  slit,  or  by  the  edge  of  an  opaque  body, 
it  is  diffracted,  and  there  arise,  as  ma}7  be  observed  upon  an  appropriately 
placed  screen,  a  series  of  dark  and  light  bands,  growing  fainter  on  the  outer 
limits.  Their  presence,  as  has  been  intimated,  is  explained  in  accordance 
with  the  undulatory  theory  of  light,  as  due  to  the  interference,  or  mutual 
reaction  of  the  adjoining  waves  of  light.  If  ordinary  light  is  employed, 
the  phenomena  are  the  same  and  for  the  same  causes,  except  that /the  bauds 
are  successive  spectra.  Diffraction  gratings,  consisting  of  a  series  of  ex- 
tremely fine  lines  very  closely  ruled  upon  glass,  are  employed  for  the  same 
purpose  as  the  prism  to  produce  the  colored  spectrum.  The  familiar 
phenomena  of  the  colors  of  thin  plates  and  of  Newton's  rings  depend  upon 
the  same  principle  of  the  interference  of  the  light  waves.  This  subject  is 
one  of  the  highest  importance  in  its  connection  with  the  optical  properties 
of  crystals,  since  the  phenomena  observed  when  they  are  viewed,  under 
certain  circumstances,  in  polarized  light  are  explained  in  an  analogous 
manner.  (Compare  the  colored  plate,  p.  144.) 


126 


PHYSICAL    CHARACTERS    OF   MINERALS. 


Polarization  by  reflection. — By  polarization  is  understood,  in  general, 
that  change  in  the  character  of  reflected  or  transmitted  light  which  dimin- 
ishes its  power  of  being  further  reflected  or  transmitted.  In  accordance 
with  the  undulatory  theory  of  light  a  ray  of  polarized  light  is  one  whose 
vibrations  take  place  in  a  single  plane  only. 

Suppose  (f.  378)  mn  and"  op  to  be  two  parallel  mirrors,  say  simple 
polished  pieces  of  black  glass ;  a  ray  of  light,  AB, 
will  be  reflected  from  mn  in  the  direction  BC\ 
and  meeting  op,  will  be  again  reflected  to  1}. 
When,  as  here,  the  two  mirrors  are  in  a  parallel 
position,  the  plane  of  reflection  is  clearly  the 
same  for  both,  the  angles  of  incidence  are  equal, 
and  the  rays  AB  and  CD  are  parallel.  The  ray 
CD  is  polarized,  although  this  does  not  show 
itself  to  the  eye  direct. 

Now  let  the  mirror,  op,  be  revolved  about  BC 
as  an  axis,  and  let  its  position  otherwise  be  un- 
changed, so  that  the  angles  of  incidence  still 
remain  equal,  it  will  be  found  that  the  reflected 
>'  ray,  CD,  loses  more  and  more  of  its  brilliancy  as 
the  revolution  continues,  and  when  the  mirror, 
op,  occupies  a  position  at  right  angles  to  its 
former  position,  the  amount  of  light  reflected  will  be  a  minimum,  the 
planes  of  reflection  being  in  the  two  cases  perpendicular  to  one  another. 

If  the  revolution  of  the  mirror  be  continued  with  the  same  conditions  as 
before,  and  in  the  same  direction,  the  reflected  ray  will  become  brighter 
and  brighter  till  the  mirror  has  the  position  indicated  by  the  dotted"  line, 
op' ,  when  the  planes  of  reflection  again  coincide,  and  the  reflected  ray,  CD ', 
is  equal  in  brilliancy  to  that  previously  obtained  for  the  position  CD. 

The  same  diminution  to  a  minimum  will  be  seen  if  the  revolution  is  con- 
tinued 90°  farther,  and  the  reflected  ray  again  becomes  as  brilliant  as  before 
when  the  mirror  resumes  its  flrst  position  op. 

In  the  above  description  it  was  asserted  that,  when  the  planes  of  inci- 
dence of  the  mirrors  were  at  right  angles  to  each  other,  the  amount  of  light 
reflected  would  be  less  than  in  any  other  position,  that  is  a  minimum.  For 
one  single  position  of  the  mirrors,.however,  as  they  thus  stand  perpendicular 
to  each  other,  that  is  for  one  single  value  of  the  angle  of  incidence,  the 
light  will  be  practically  extinguished,  and  no  reflected  ray  will  appear 
from  the  second  mirror. 

The  angle  of  incidence,  ABH,  for  this  case  is  called  the  angle  of  polar- 
ization, and  its  value  varies  for  different  substances.  It  was  shown  further 
by  Brewster  that : 

The  angle  of  polarization  is  that  angle  whose  tangent  is  the  index  of 
refraction  of  the  reflecting  substance,  i.e.,  tan  i  =  n. 

Exactly  the  same  phases  of  change  would  have  been  observed  if  the 
upper  mirror  had  been  revolved  in  a  similar  manner.  The  first  mirror  is 
often  called  the  polarizer,  the  second  the  analyzer. 

This  change  which  the  light  suffers  in  this  case,  in  consequence  of  re- 
flection, is  u&{\edi  polarization. 

In  order  to  give  a  partial  explanation  of  this  phenomenon  and  to  make 


POLARIZATION    OF   LIGHT.  127 

the  same  subject  intelligible  as  applied  to  other  cases  in  which  polarization 
occurs,  reference  must  be  made  to  the  commonly  received  theory  of  the 
nature  of  light  already  defined. 

The  phenomena  of  light  are  explained,  as  has  been  stated,  on  the  assump- 
tion that  it  consists  of  the  vibrations  of  the  ether,  the  vibrations  being 
transverse,  that  is  in  a  plane  perpendicular,  to  the  direction  in  which  the 
light  is  propagated  These  vibrations  in  ordinary  light  take  place  in  all 
directions  in  this  plane  at  sensibly  the  same  time  ;  strictly  speaking,  the 
vibrations  are  considered  as  being  always  transverse,  but  their  directions 
are  constantly  and  instantaneously  changing  in  azimuth.  Such  a  ray  of  light 
is  alike  011  all  sides  or  all  around  the  line  of  propagation,  AB,  f.  374. 
A  ray  of  completely  polarized  light,  on  the  other  hand,  has  vibrations  in 
one  direction  only,  that  is  in  a  single  plane. 

These  principles  may  be  applied  to  the  case  of  reflection  already  de- 
scribed. The  ra}7  of  ordinary  light,  A.B,  has  its  vibrations  sensibly  simul- 
taneous in  all  directions  in  the  plane  at  right  angles  to  its  line  of  propaga- 
tion, while  the  light  reflected  from  each  mirror  has  only  those  vibrations 
which  are  in  one  direction,  at  right  angles  to  the  plane  of  reflection — 
supposing  that  the  mirrors  are  so  placed  that  the  angle  of  incidence 
(ASH)  is  also  the  angle  of  polarization. 

If  the  mirror  occupy  the  position  represented  in  f.  378,  the  ray  of  light, 
BC,  after  being  reflected  by  the  first  mirror,  mn,  contains  that  part  of  the 
vibrations  whose  direction  is  normal  to  its  plane  of  reflection  called  the 
plane  of  polarization,.  This  is  also  true  of'  the  second  mirror,  and  when 
they  are  parallel  and  their  planes  of  reflection  coincide,  the  ray  of  light  is 
reflected  a  second  time  without  additional  change. 

If,  however,  the  second  mirror  is  revolved  in  the  way  described  (p.  126), 
less  and  less  of  the  light  will  be  reflected  by  it,  since  a  successively  smaller 
part  of  the  vibrations  of  the  ray  ^67take  place  in  a  direction  normal  to 
its  plane  of  reflection.  And  when  the  mirrors  are  at  right  angles  to  each 
other,  after  a  revolution  of  op  90°  about  the  line  ^?67as  an  axis,  no  part  of 
the  vibrations  of  the  ray  B  O  are  in  the  plane  at  right  angles  to  the  reflec- 
tion-plane of  the  second  mirror,  and  hence  the  light  is  extinguished. 

By  reference  to  f.  375  this  subject  may  be  explained  a  little  more  broadly. 
It  was  seen  that  of  the  ray  ca,  meeting  the  surface  of  the  water  at  #,  part  is 
reflected  and  part  transmitted  in  accordance  with  the  laws  of  reflection 
and  refraction.  It  has  been  shown  further  that  the  reflected  ray  is  polar- 
ized, that  is,  it  is  changed  so  that  the  vibrations  of  the  light  take  place  in 
one  direction,  at  right  angles  to  the  plane  of  incidence.  It  is  also  true  that 
the  refracted  ray  is  polarized,  it  containing  only  those  vibrations  which 
were  lost  in  the  reflected  ray,  that  is,  those  which  coincide  with  the  plane 
of  incidence  and  reflection. 

It  was  stated  that  the  vibrations  of  the  polarized  reflected  ray  take  place 
at  right  angles  to  the  plane  of  polarization.  This  is  the  assumption  which 
is  commonly  made ;  but  all  the  phenomena  of  polarization  can  be  equally 
well  explained  upon  the  other  supposition  that  they  coincide  with  this 
plane. 

The  separation  of  the  ray  of  ordinary  light  into  two  rays,  one  reflected 
the  other  refracted,  vibrating  at  right  angles  to  each  other,  takes  place  most 
completely  when  the  reflected  and  refracted  rays  are  90°  from  one  another, 


128  PHYSICAL    CHARACTERS    OF   MINERALS. 

as  proved  by  Brewster.  From  this  fact  follows  the  law  already  stated, 
that  the  tangent  of  the  angle  of  polarization  is  equal  to  the  index  of  re- 
fraction. The  angle  of  polarization  for  glass  is  about  54°  35'. 

This  separation  is  in  no  case  absolutely  complete,  but  varies  with  differ- 
ent substances.  In  the  case  of  opaque  substances  the  vibrations  belonging 
to  the  refracted  ray  are  more  or  less  completely  absorbed  (compare  remarks 
on  color,  p.  164).  Metallic  surfaces  polarize  the  light  very  slightly. 

Polarisation  by  means  of  thin  plates  of  glass. — It  has  been  explained 
that. the  light  which  has  been  transmitted  and  refracted  is  always  at  least 
in  part  polarized.  It  will  be  readily  understood  from  this  fact  that  when  a 
number  of  glass  plates  are  placed  together,  the  light  which  passes  through 
them  all  will  be  more  and  more  completely  polarized  as  their  number  is 
increased.  This  is  a  second  convenient  method  of  obtaining  polarized 
light. 

Polarization  ~by  means  of  tourmaline  plates. — The  phenomena  of  polar- 
ized light  may  also  be  shown  by  means  of  tourmaline  plates.  If  from 
a  crystal  of  tourmaline,  which  is  suitably  transparent,  two  sections  be 
obtained,  each  cut  parallel  to  the  vertical  axis,  it  will  be  found  that 
these,  when  placed  together  with  the  direction  of  their  axes  coinciding, 
allow  the  light  to  pass  through.  If,  however,  one  section  is  revolved  upon 
the  other,  less  and  less  of  the  light  is  transmitted,  until,  when  their  axes  are 
at  right  angles  (90°)  to  each  other,  the  light  is  (for  the  most  part)  extin- 
guished. As  the  revolution  is  continued,  more  and  more  light  is  obtained 
through  the  sections,  and  after  a  revolution  of  180°,  the  axes  being  again 
parallel,  the  appearance  is  as  at  first.  A  further  revolution  (270°)  brings 
the  axes  again  at  right  angles  to  each  other,  when  the  light  is  a  second  time 
extinguished,  and  so  on  around. 

The  explanation  of  these  phenomena,  so  far  as  it  can  be  given  here,  is 
analogous  to  that  employed  for  the  case  of  polarization  by  re- 
379  flection.       Each   plate  so   affects  the   ray    of  light  that  after 

a^^^^b      having  passed  through  it  there  exist  vibrations  in  one  direction 
HI    ID      °nlj?  aild  that  parallel  to  the  vertical  axis,  the  other  vibrations 
being  absorbed.     If  now  the  two  plates  are  placed  in  the  same 
position,  abde,  and  efgh  (f.  379),  the  light  passes  through  both 
in  succession.     If,  however,  the  one  is  turned  upon  the  other, 
Hi      only  that  portion  of  the  light  can  pass  through  which  vibrates 
j/*~      ^       still  in  the  direction  ao.      This  portion  is  determined  by  the 
resolution  of  the  existing   vibrations  in  accordance   with  the 
principle  of  the  parallelogram  of  forces.     Consequently,  when  the  sections 
stand  at  right  angles  to  each  other  (f.  380)  the  amount  of 
transmitted  light  is  nothing  (not  strictly  true),  that  is,  the 
light  is  extinguished. 

The  tourmaline  plates,  which  have  been  described,  are 
mounted  in  pieces  of  cork  and  held  in  a  kind  of  wire 
pincers  (f.  381).  The  object  to  be  examined  is  placed 
between  them  and  supported  there  by  the  spring  in  the 
wire.  In  use  they  are  held  close  to  the  eye,  and  in 
this  position  the  object  is  viewed  in  converging  polarized  light. 

Polarization  by  means  of  Nicol  prisms. — The  most  convenient  method 
of  obtaining  polarized  light  is  by  means  of  a  Nicol  prism  of  calcite.  A 


POLARIZATION   OF   LIGHT. 


129 


cleavage  rhombohedron  of  calcite  (the  variety  Iceland  spar  is  universally 
used  in  consequence  of  its  transparency)  is  obtained,  having  four  large  and 
two  small  rhombohedral  faces  opposite  each  other.  In  place  of  the  latter 


382 


planes  two  new  surfaces  are  cut,  making  angles  of  68°  (instead  of  71°)  with 

the  obtuse  vertical  edges ;  these  then  form  the  terminal  faces  of  the  prism. 

In  addition  to  this,  the  prism  is  cut  through  in  the  direction  HH  (f.  382), 

the  parts  then  polished  and  cemented  together  again  with 

Canada  balsam.     A  ray  of  light,  ab,  entering  the  prism 

is  divided  into  two  rays  polarized  at  right  angles  to  each 

other.     One  of  these,  bo,  on  meeting  the  layer  of  balsam 

(whose  refractive  index  is  greater  than   that  of  calcite) 

suffers  total  reflection  (p.  124),  and  is  deflected  against  the 

blackened  sides  of  the  prism  and  extinguished.     The  other 

passes  through  and  emerges  at  e,  a  completely  polarized 

ray  of  light,  that  is,  a  ray  with  vibrations  in  one  direction 

only,  and  that  the  direction  of  the  shorter  diagonal  of  the 

prism  (f.  383). 

It  is  evident  that  twoNicol  prisms  can  be  used  together 
in  the  same  way  as  the  two  tourmaline  plates,  or  the  two 
mirrors ;  one  is  called  the  polarizer,  and  the  other  the 
analyzer.  The  plane  of  polarization  of  the  Nicol  prisms 
has  the  direction  PP  (f .  383)  at  right  angles  to  which  the 
vibrations  of  the  light  take  place.  A  ray  of  light  pass- 
ing through  one  Nicol  will  be  extinguished  by  a  second 
when  its  plane  of  polarization  is  at  right  angles  to  that  of 
the  first  prism  ;  in  this  case  the  Nicols  are  said  to  be 
crossed.  The  Kicol  prisms  have  the  great  advantage  over  the  tourmaline 
plates,  that  the  light  they  transmit  is  uncolored  and  more  completely 
polarized. 

Either  a  tourmaline  plate  or  a  Nicol  prism 
may  also  be  used  in  connection  with  a  reflecting 
mirror.      The  light  reflected  by  such  a  mirror 
vibrates  in  a  plane  at  right  angles  to  the  plane  of 
incidence    (plane  of  polarization) ;    that    trans- 
mitted by  the  Nicol  prism  vibrates  in  the  direc- 
tion   of  the    shorter  diagonal  (f.  383).     Hence, 
when  the  plane  of  this  diagonal  is  at  right  angles 
to  the  plane  of  polarization  of  the  mirror,  the  re- 
flected ray  will  pass  through  the  prism  ;  but  when  the  two  planes  mentioned 
coincide,  the  planes  of  vibration  are  at  right  angles  and  the  reflected  ray  is 
extinguished  by  the  prism. 
9 


130 


PHYSICAL    CHARACTERS    OF    MINERALS. 


Polariscopes.—The  Nicol  prisms,  when  ready  for  use,  are  mounted  in  an 
upright  instrument,  called  a  polariscope.  Sometimes  parallel,  and  some- 
times converging,  light  is  required  in  the  investigations  for  which  the  instru- 
ment is  used.  Fig.  384  shows  the  polarization-microscope  of  Norrenberg 


as  altered  and  improved  by  Groth  (see 
Literature,  p.  156).  The  Nicol  prisms 
are  at  d  and  r,  and  are  so  mounted  as 
to  admit  of  a  motion  of  revolution  in- 
dependent of  the  other  parts  of  the  in- 
strument. The  lense  e  causes  the  light 
from  the  ordinary  mirror,  a,  to  pass  as  a 
cone  through  the  prism  d,  and  the  lenses 
at  A  converge  the  light  upon  the  plate 
to  be  examined  placed  at  i.  The  other 
lenses  (o)  above  act  as  a  weak  microscope, 
having  a  field  of  vision  of  130°.  The 
stage  (£atid  k\  carrying  the  object,  admits 
of  a  horizontal  revolution.  The  distance 

' ^ '      between  the  two  halves  of  the  instrument 

is  adjusted  by  the  screws  m  and  n. 
When  parallel  light  is  required,  a  similar  instrument  is  employed,  which 

lias,  however,  a  different  arrangement  of  the  lenses,  as  shown  in  f.  385. 

The  objects  for  which  these  instruments,  as  well  as  the  tourmaline  plates, 

are  employed,  will  be  found  described  in  the  following  pages. 

The  Nicol  prisms  are  often  used  as  an  appendage  to  the  ordinary  com 

pound  microscope,  and  in  this  form  are  important  as  enabling  us  to  examine 

very  minute  crystals  in  polarized  light. 


OPTICAL    CHARACTERS    OF   ISOMETRIC   CRYSTALS.  131 


DISTINGUISHING    OPTICAL    CHARACTERS   OF    THE  CRYS- 
TALS  OF   THE  DIFFERENT   SYSTEMS. 

It  has  already  been  remarked  that  all  crystallized  minerals  group  them- 
selves into  three  grand  classes,  which  are  distinguished  by  their  physical 
properties,  as  well  as  their  geometrical  form : 

A..  Isometric,  in  which  the  crystals  are  developed  alike  in  all  the  several 
axial  directions. 

B.  Lsodiametric,  including  the  tetragonal  and  hexagonal  systems,  whose 
crystals  are  alike  in  the  directions  of  the  several  lateral  axes,  but  vertically 
the  development  is  unlike  that  laterally. 

C.  Anisometric,  embracing  the  three  remaining  systems,  where  the  crys- 
tals are  developed  in  the  three  axial  directions  dissimilarly. 

Between  these  classes  there  are  many  cases  of  gradual  transition  in  crystalline  form,  and, 
similarly  and  necessarily,  in  optical  character.  The  line  between  uniaxial  and  biaxial 
crystals,  for  instance,  cannot  be  considered  a  very  sharply  denned  one. 


A.  ISOMETRIC  CRYSTALS. 
General  Optical  Character. 

All  isometric  crystals  are  alike  in  this  respect  that  they  simply  refract, 
but  do  not  doubly  refract  the  light  they  transmit.  They  _  are  optically 
isotrope.  This  follows  directly  from  the  symmetry  of  the  crystallization. 
In  the  language  of  Fresnel,  the  elasticity  of  the  light-ether  is  throughout 
them  the  same,  and  the  light  is  propagated  in  every  direction  with  the 
same  velocity.  There  is,  consequently,  but  one  value  of  the  index  of  refrac- 
tion. The  wave-surface  is  spherical.  This  class  also  includes  all  trans- 
parent amorphous  substances,  like  glass. 


Optical  Investigation  of  Isometric  Crystals. 

In  consequence  of  their  isotropic  character,  isometric  crystals  exhibit  no 
special  phenomena  in  polarized  light.  Sections  of  isometric  crystals  may 
be  always  recognized  as  such  by  the  fact  that  they  behave  as  an  amorphous 
substance  in  polarized  light; 'in  other  words,  when  the  Nicol  prisms  are 
crossed  they  appear  dark,  and  a  revolution  of  the  section  in  any  plane  pro- 
duces no  change  in  appearance.  Similarly  they  appear  light  when  placed 
between  parallel  Nicols.  Some  anomalies  are  mentioned  on  p.  154. 

Isometric  crystals  havTe  but  a  single  index  of  refraction,  and  that  may  be 
determined  in  the  way  described  by  means  of  a  prism  cut  with  its  edge  in 
any  direction  whatever. 

Crystals  of  the  second  and  third  classes  are  optically  anisotrope. 


132 


PHYSICAL    CHARACTERS    OF    MINERALS. 


386 


B.  UNIAXIAL  CRYSTALS. 
General  Optical  Character. 

In  the  isodiametric  crystals,  those  of  the  tetragonal  and  hexagonal  sys- 
tems, there  is  crystallographically  one  axial  direction,  that  of  the  vertical 
axis,  which  is  distinguished  from  the  other  lateral  directions  which  are 
among  themselves  aljike.  So  also  the  optical  investigations  of  these  crystals 
show  that  with  reference  to  the  action  of  light  there  exists  a  similar  kind 
of  symmetry.  Light  is  propagated  in  the  direction  of  the  vertical  axis  with 
a  velocity  different  from  that  with  which  it  passes  in  any  other  direction, 
but  for  all  directions  at  right  angles  to  the  vertical  axis,  or  all  directions 
making  the  same  angle  with  it,  the  velocity  of  propagation  is  the  same. 
In  other  words,  the  elasticity  of  the  ether  in  the  direction  of  the  vertical 
axis  is  either  greater  or  less  than  that  in  directions  normal  to  it  (analogous 
to  the  crystallographical  relation  c  ^  a)9  while  in  the  latter  directions  it  is 
everywhere  alike. 

Optic  axis. — Let  a  ray  of  light  pass  through 
the  crystal  in  the  direction  of  the  vertical  axis, 
ab,  in  f.  386,  its  vibrations  must  take  place  in 
the  plane  at  right  angles  to  this  axis  ;  but  in  all 
directions  in  this  plane  the  elasticity  of  the  ether 
is  the  same,  hence  for  such  a  ray  the  crystal  must 
act  as  an  isotrope  medium ;  and  the  ray  is  con- 
sequently not  doubly  refracted  and  not  polarized. 
This  direction  is  called  the  OPTIC  AXIS.* 

Double  refraction. — If,  on  the  other  hand,  the 
ray  of  light  passes  through  the  crystal  in  any  other  direction,  it  is  divided 
into  two  rays,  or  doubly  refracted  (see  f.  377),  and  this  in  consequence  of: 
the  difference  in  the  elasticity  of  the  ether  in  the  plane  in  which  .the  vibra- 
tions take  place.  Of  these  two  rays,  one  follows  the  law  of  ordinary 
refraction,  and  this  is  called  the  ordinary  ray  ;  the  other  does  not  conform 
to  this  law,  and  is  called  the  extraordinary  ray.  Both  these  rays  are  polar- 
ized, and  in  planes  at  right  angles  to  each  other ;  the  vibrations  of  the 
extraordinary  ray  take  place  in  the  plane  passing  through  the  incident  ray 
and  vertical  axis,  called  the  principal  section,  those  of  the  ordinary  ray 
are  in  a  plane  at  right  angles  to  this. 

Wave-surface  of  the  ordinary  ray. — The  meaning  of  the  statement  that 
the  ordinary  ray  follows  the  law  of  the  simple  refraction  is  this  : — the  index 
of  refraction  (o>)  of  the  ordinary  ray  has  invariably  the  same  value,  what- 
ever be  the  direction  in  which  the  light  passes  through  the  crystal ;  the 
amount  of  deviation  from  the  perpendicular  is  always  in  accordance  with 

the  law  -    -  =  n  (o>).     In  other  words,  the  ordinary  ray  is  propagated  in 

Sill  '/* 

all  directions  in  the  medium  with  the  same  velocity ;  and  hence  the  wave- 


*  It  will  be  understood  that  the  optic  axis  is  always  a  direction,  not  a  fixed  line  in  the 
crystals. 


OPTICAL   CHARACTERS    OF    UNIAXIAL    CRYSTALS. 


133 


surface  is  that  of  a  sphere.     Moreover,  the  ordinary  ray  always  remains  in 
the  plane  of  incidence. 

Wave-surface  of  the  extraordinary  ray. — For  the  extraordinary  ray  the 
law  of  simple  refraction  does  not  hold  good.  If  experiments  be  made  upon 
any  uniaxial  crystal,  it  will  be  found  that  the  two  rays  are  most  separated 
when  (1)  the  light  falls  PERPENDICULAR  to  the  vertical  axis.  As  its  inclina- 
tion toward  the  axis  is  diminished,  the  extraordinary  ray  approaches  the 
ordinary  ray,  and  coincides  with  it  when  (2)  the  light  passes  through  PAR- 
ALLEL to  the  vertical  axis.  The  index  of  refraction  of  the  extraordinary  ray 
varies  in  value,  being  most  unlike  o>  for  the  first  case  supposed  when  the 
vibrations  of  the  extraordinary  ray  are  parallel  to  the  axis  (when  it  is 
called  e),  and  is  equal  to  o>  for  the  second  case  supposed.  The  velocity  of 
this  ray  is  then  variable  in  a  corresponding  manner.  The  wave-surface  of 
the  extraordinary  ray  is  an  ellipsoid  of  rotation.  Moreover  it  ordinarily 
does  not  remain  in  the  plane  of  incidence. 

Two  cases  are  now  possible :  the  index  (o>)  of  the  ordinary  ray  may  be  (1) 
greater  than  that  of  the  extraordinary  ray  (e),  in  which  case  the  velocitv  of 
the  light  in  the  direction  of  the  vertical  axis  is  less  than  that  in  any  other 
direction  ;  or  (2)  o>  may  be  less  than  e,  and  in  this  case  the  velocity  of  pro- 
pagation for  the  light  has  its  maximum  parallel  to  the  vertical  axis.  The 
former  are  called  negative,  the  latter  positive  crystals.  The  fact  alluded 
to  here  should  be  noted  that  the  value  of  the  refractive  index  is  inversely 
proportional  to  the  velocity  of  the  light,  or  elasticity  of  the  ether,  in  the 
given  direction. 

Negative  crystals  ;  Wave-surface. — For  calcite  w  =1-654,  €  —  1-483,  it  is 
hence  one  of  the  class  of  negative  crystals.  The  former  value  (w)  belongs 
to  the  ray  vibrating  at  right  angles  to  the  vertical  axis,  and  the  latter  value 
(e)  to  the  ray  with  vibrations  parallel  to  the  axis.  As  has  been  stated,  the 
refractive  index  for  the  extraordinary  ray  increases  from  1.483  to  1.654,  as 
the  ray  becomes  more  and  more  nearly 
parallel  to  the  vertical  axis.  F*ig.  387  illus- 
trates graphically  the  relation  between  the 
two  indices  of  refraction,  and  the  correspond- 
ing velocities  of  the  rays  ;  ab  represents  the 
d  irection  of  the  vertical  axis,  that  is,  the  optic 
axis.  Also  ma,  mb  represent  the  velocity 
of  the  light  parallel  to  this  axis,  correspond- 
ing to  the  greater  index  of  refraction  (1*654). 
The  circle  described  with  this  radius  will 
represent  the  constant  velocity  of  the  ordi- 
nary ray  in  any  direction  whatever.  Let 
further  md,  me  represent  the  velocity  of  the  extraordinary  ray  passing,  at 
right  angles  to  the  axis,  hence  corresponding  to  the  smaller  index  of 
refraction  (1*483).  The  ellipse,  whose  major  and  minor  axes  are  cd 
and  ab,  will  express  the  law  in  accordance  with  which  the  velocity  of  the 
extraordinary  ray  varies,  viz.,  greatest  in  the  direction  md,  least  in  the 
direction  ab  in  which  it  coincides  with  the  ordinary  ray.  For  any  inter- 
mediate direction,  hgm,  the  velocity  will  be  expressed  by  the  length  of  the 
line,  Jim. 

Now  let  this  figure  be  revolved  about  the  axis  ab ;  there  will  be  generated 


387 


134 


PHYSICAL    CHARACTERS    OF    MINERALS. 


a  circle  within  an  oblate  ellipsoid  of  rotation  (f.  388).     The  surface  of  the 

sphere  is  the  wave-surface  of  the  ordinary  ray, 
and  that  of  the  ellipsoid  of  the  extraordinary 
ray  ;  the  line  of  their  intersection  is  the  optic 
axis. 

In  f.  377,  p.  125,  the  ray  of  light  is  shown 
divided  into  two  by  the  piece  of  calcite  ;  of 
these,  fid,  which  is  the  more  refracted,  is  the 
ordinary  ray,  and  cd,  which  is  less  refracted,  is 
the  extraordinary  ray. 

Positive  crystals  ;  Wave-surface.  —  For 
quartz  o>  =  1'548,  e  =  1-558.  The  index  of 
refraction  for  the  ordinary  ray  (o>)  is  less  than  that  of  the  extraordinary  ray 
(e)  ;  quartz  hence  belongs  to  the  class  of  positive  crystals.  The  value  of  e 
(1*558)  for  the  extraordinary  ray  corresponds  to  the  direction  of  the  ray  at 
right  angles  to  the  vertical  axis,  when  its  vibrations  are  parallel  to  this  axis. 
As  the  direction  of  the  ray  changes  and  becomes  more  and  more  nearly  par- 

allel to  the  axis,  the  value  of  its  index  of  re- 
fraction decreases,  and  when  it  is  parallel  to  the 
latter,  it  has  the  value  1-548.  The  extraordin- 
ary ray  then  coincides  with  the  ordinary,  and 
there  is  no  double  refraction  ;  this  is,  as  be- 
fore, the  line  of  the  optic  axis.  The  law  for 
both  rays  can  be  represented  graphically  in 
the  same  way  as  for  negative  crystals.  In 
f  .  389,  amb  is  the  direction  of  the  optic  axis  ; 
let  ma,  mb  represent  the  velocity  of  the  ordin- 
ary ray,  which  corresponds  to  the  least  re- 
fractive index  (1'548),  the  circle  afbe  will 
express  the  law  for  this  ray,  viz.,  the  velocity 
the  same  in  every  direction.  Moreover,  let 
j  me  represent  the  velocity  of  the  extraor- 


dinary ray,  at  right  angles  to  the  axis,  which  corresponds  to  the  maximum 
refractive  index  (1*558)  ;  the  ellipse,  adbc,  will  express  the  law  for  velocity 
of  the  extraordinary  ray,  viz  ,  least  in  the  direction  md,  and  greatest  in  the 
direction  ab,  when  it  is  equal  to  that  of  the  ordinary  ray,  and  varying 
uniformly  between  these  limits.  If  the  figure  be  revolved  as  before,  there 
will  be  generated  a  sphere,  whose  surface  is  the  wave-surface  of  the  ordin- 
ary ray,  and  within  it  a  prolate  ellipsoid  whose  surface  represents  the 
wave-surface  of  the  extraordinary  ray. 

The  following  list  includes  examples  of  both  classes  of  uniaxial  crystals  : 


Negative  crystals  (— ), 
Calcite, 
Tourmaline, 
Corundum, 
Beryl, 
Apatite. 


Positive  crystals  (+), 
Quartz, 
Zircon, 
Hematite, 
Apophyllite, 
Cassiterite. 


It  may  be  remarked  that  in  some  species  both  -h  and  —  varieties  have 


OPTICAL   CHARACTERS    OF    UNI  AXIAL   CRYSTALS.  135 

been  observed.  Certain  crystals  of  apophyllite  are  positive  for  one 
end  of  the  spectrum  and  negative  for  the  other,  and  consequently  for  some 
color  between  the  two  extremes  it  has  no  double  refraction. 

These  principles  make  the  explanation  of  the  use  of  tourmaline  plates  and  calcite  prisms 
as  polarizing  instruments  (p.  128)  more  intelligible. 

The  two  rays  into  which  the  single  ray  is  divided  on  passing  through  a  uniaxial  crystal  are, 
as  has  been  said,  both  polarized,  the  ordinary  ray  in  a  plane  passing  through  the  vertical 
axis  and  the  extraordinary  ray  perpendicular  to  this.  In  a  tourmaline  plate  of  the  proper 
thickness,  cut  parallel  to  the  axis  4,  the  ordinary  ray  is  absorbed  (for  the  most  part)  and  the 
extraordinary  ray  alone  passes  through,  having  its  vibrations  in  the  direction  of  the  vertical 
axis. 

In  the  calcite  prism,  of  the  two  refracted  and  polarized  rays,  the  ordinary  ray  is  disposed  of 
artificially  in  the  manner  mentioned  (p.  129),  and  the  extraordinary  ray  alone  passes  through, 
vibrating  as  already  remarked,  in  the  direction  of  the  axis  c,  or,  in  other  words,  of  the 
shorter  diagonal  of  the  Nicol  prism . 

The  relation  of  these  phenomena  to  the  molecular  structure  of  the  crystal  is  well  shown 
by  the  effect  of  pressure  upon  a  parallelepiped  of  glass  Glass,  normally,  exhibits  no  colored 
phenomena  in  polarized  light,  since  the  elasticity  of  the  ether  is  the  same  in  all  directions, 
and  there  is  hence  no  double  refraction.  But  if  the  block  be  placed  under  pressure,  exerted 
on  two  opposite  faces,  the  conditions  are  obviously  changed,  the  density  is  the  same  in  the 
both  lateral  directions  but  differs  from  that  in  the  direction  of  the  axis  of  pressure.  The  sym- 
metry in  molecular  structure  becomes  that  of  a  uniaxial  crystal,  and,  as  would  be  expected, 
on  placing  the  block  in  the  polariscope,  a  black  cross  with  its  colored  rings  is  observed,  exactly 
as  with  calcite.  Similarly  when  glass  has  been  suddenly  and  unevenly  cooled  its  molecular 
structure  is  not  homogeneous,  aad  it  will  be  found  to  polarize  light,  although  the  phenomena, 
for  obvious  reasons,  will  not  have  the  regularity  of  the  case  described. 

It  may  be  added  here  that  recent  investigations  by  Mr.  John  Kerr  have  shown  that  electri- 
city calls  out  birefringent  phenomena  in  a  block  of  glass.  (Phil.  Mag.,  1.,  337.) 


Optical  Investigation  of  Uniaxial  Crystals. 

Sections  normal  or  parallel  to  the  axis  in  polarized  light. — Suppose  a 
section  to  be  cut  perpendicular  to  the  vertical  axis  (axial  section),  it  has 
already  been  shown  that  a  ray  of  light  passing  through  the  crystal  in  this 
direction  suffers  no  change,  consequently,  such  a  section  examined  in 
parallel  polarized  light,  in  the  instrument  (f.  385),  appears  as  a  section  of 
an  isometric  crystal. 

If  the  same  section  be  placed  in  the  other  instrument  (f.  384,  p.  130), 
arranged  for  viewing  the  object  in  converging  light,  or  in  the  tourmaline 
tongs,  a  beautiful  phenomenon  is  observed  ;  a  symmetrical  black  cross — 
when  the  Xicois  or  tourmaline  plates  are  crossed — with  a  series  of  concentric 
rings,  dark  and  light,  in  monochromatic  light,  but  in  white  light,  showing 
the  prismatic  colors  in  succession  in  each  ring.  This  is  shown  without  the 
colors  in  f.  390,  the  arrangement  of  the  colors  in  the  elliptical  rings  of  the 
plate  opposite  page  144  is  similar. 

This  cross  becomes  white  when  the  Nicols  or  tourmalines  are  in  a  par- 
allel position,  and  each  band  of  color  in  white  light  changes  to  its  comple- 
mentary tint  (f.  391).  These  interference  figures  are  seen*  in  this  form 
only  in  a  plate  cut  perpendicular  to  the  vertical  axis,  and  marks  the  uni- 
axial character  of  the  crystal. 

The  explanation  of  this  phenomenon  can  be  only  hinted  at  in  this  place. 

*  Uniaxial  crystals  which  produce  circular  polarization  exhibit  interference  figures  which 
differ  somewhat  from  those  described.  Some  anomalies  are  mentioned  on  p.  154. 


136  PHYSICAL    CHARACTERS    OF   MINERALS. 

All  the  rays  of  light,  whose  vibrations  coincide  with  the  vibration-planes 
of  either  of  the  crossed  Nicols,  must  necessarily  be  extinguished.  This 
gives  rise  to  the  black  cross  in  the  centre,  with  its  arms  in  the  direction  of 
the  planes  mentioned.  .All  other  rays  passing  through  the  given  plate 
obliquely  will  be  doubly  refracted,  and  after  passing  through  the  second 
Nicol,  thus  being  referred  to  the  same  plane  of  polarization,  they  will 


390 


interfere,  and  will  give  rise  to  a  series  of  concentric  rings,  light  and  dark 
in  homogeneous  light,  but  in  ordinary  light  showing  the  successive  colors  of 
the  spectrum.  In  regard  to  the  interference  of  polarized  rays,  the  fact  must 
be  stated  that  that  can  take  place  only  when  they  vibrate  in  the  same  plane  ; 
two  rays  vibrating  at  right  angles  to  each  other  cannot  interfere.  These 
interference  phenomena  are  similar  to  the  successive  spectra  obtained  by 
diffraction  gratings  alluded  to  on  p.  125.  It  is  evident  that,  in  order  to 
observe  the  phenomena  most  advantageously,  the  plate  must  have  a  suitable 
thickness,  which,  however,  varies  with  the  refractive  index  of  the  substance. 
The  thicker  the  plate  the  smaller  the  rings  and  the  more  they  are  crowded 
together ;  when  the  thickness  is  considerable,  only  the  black  brushes  are 
seen. 

Section  parallel  (or  sharply  inclined)  to  the  axis. — If  a  section  of  a  uni- 
axial  crystal,  cut  parallel  or  inclined  to  the  vertical  axis,  be  examined  in 
parallel  polarized  light,  it  will,  when  its  axis  coincides  with  the  direction 
of  vibration  of  one  of  the  Nicol  prisms,  appear  dark  when  the  prisms  are 
crossed.  If,  however,  it  be  revolved  horizontally  on  the  stage  of  the  polari- 
scope  (7,  Z,  f.  384)  it  will  appear  alternately  dark  and  light  at  intervals  of  45°, 
dark  under  the  conditions  mentioned  above,  otherwise  more  or  less  light,  the 
maximum  of  light  being  obtained  when  the  axis  of  the  section  makes  an 
angle  of  45°  with  the  plane  of  the  Nicol.  Between  parallel  Nicols  the 
phenomena  are  the  same  except  that  the  light  and  darkness  are  reversed. 
When  the  plate  is  not  too  thick  the  polarized  ray,  after  passing  the  upper 
Nicol,  will  interfere,  and  in  white  light,  the  plate  will  show  bright  colors, 
which  change  as  one  of  the  Nicols  or  the  plate  is  revolved. 

Examined  in  converging  light,  similar  sections,  when  very  thin,  show  in 
white  light  a  series  of  parallel  colored  bands. 

Determination  of  the  indices  of  refraction  co  and  e. — One  prism  will 


OPTICAL    CHARACTERS    OF    UNI  AXIAL   CRYSTALS.  137 

suffice  for  the  determination  of  both  indices  of  refraction,  and  its  edge  may 
be  either  parallel  or  perpendicular  to  the  vertical  axis. 

(a)  If  parallel  to  the  vertical  axis,  the  angle  of  minimum  deviation  for 
each  ray  in  succession  must  be  measured.     The  extraordinary  ray  vibrates 
parallel  to,  and  the  ordinary  ray  at  right  angles  to,  the  direction  of  the  edge 
of  the  prism.     For  convenience  it  is  better  to  isolate  each  of  the  rays  in 
succession,  which  is  done  with  a  single  Nicol  prism.     If  this  is  held  before 
the  observing  telescope  with  its  shorter  diagonal  parallel  to  the  refracting 
edge  of  the  prism,  the  ordinary  ray  will  be  extinguished  and  the  image  of 
the  slit  observed  will  be  that  due  to  the  extraordinary  ray.     If  held  with  its 
plane  of  vibration  at  right  angles  to  the  prismatic  edge,  the  extraordinary 
ray  will  be  extinguished  and  the  other  alone  observed.     From  the  single 
observed  angle,  for  the  given  color,  the  index  of  refraction  can  be  calculated, 
a)  or  e,  by  the  formula  given  on  p.  124,  the  angle  of  the  prism  being  known. 

(b)  If  the  refracting  edge  of  the  prism  is  perpendicular  to  the  vertical 
axis  of  the  crystal,  the  same  procedure  is  necessary,  only  in  this  case  the 
ordinary  ray  will  vibrate  parallel  to  the  prismatic  edge,  and  the  extraordi- 
nary ray  at  right  angles  to  it.    The  two  rays  are  distinguished,  as  before,  by 
a  Nicol  prism. 

Determination  of  the  positive  or  negative  character  of  the  double  refrac- 
tion.— The  most  obvious  way  of  determining  the  character  of  the  double 
refraction  (CD  >  e  or  co  >  e)  is  to  measure  the  indices  of  refraction  in  accord- 
ance with  the  principles  explained  in  the  preceding  paragraphs.  It  is  not 
always  possible,  however,  to  obtain  a  prism  suitable  for  this  purpose,  and  in 
any  case  it  is  convenient  to  have  a  more  simple  method  of  accomplishing 
the  result. 

To  do  this,  use  may  be  made  of  a  very  simple  principle  : — the  +  or  - 
character  of  a  given  crystal  is  determined  by  observing  the  effect  produced 
when  an  axial  section  from  it  is  combined  in  the  polariscope  with  that  of  a 
crystal  of  known  character. 

For  instance,  calcite  is  negative,  and  if  it  be  placed  in  conjunction  with 
the  section  of  a  positive  crystal,  the  whole  effect  observed  is  the  same  as  that 
which  would  be  produced  if  the  original  plate  were  diminished  in  thickness, 
while,  if  combined  with  a  negative  crystal,  it  is  as  if  the  plate  were  made 
thicker.  It  has  already  been  remarked  that,  as  the  axial  plate  of  a  crystal 
increases  in  thickness,  the  number  of  rings  visible  in  the  field  of  the  polari- 
scope increases,  and  they  become  more  crowded  together ;  but,  if  the  section 
is  made  thinner,  the  successive  rings  widen  out  and  become  less  numerous. 
One  or  the  other  of  these  effects  is  produced  by  the  use  of  the  intervening 
section. 

In  the  case  of  uniaxial  crystals,  however,  the  method  which  is  practically 
most  simple  is  that  suggested  by  Dove — the  use  of  an  axial  plate  of  mica  of 
a  certain  thickness.  The  section  required  is  a  cleavage  piece  of  such  a 
thickness  that  the  two  rays  in  passing  through  suffer  a  difference  of  phase 
which  is  equal  to  a  quarter  wave-length,  or  an  odd  multiple  of  this. 

Suppose  that  the  section  of  the  crystal  to  be  examined,  cut  perpendicular 
to  the  axis,  is  brought  between  the  crossed  Nicols  in  the  polariscope ;  the 
black  cross  and  the  concentric  colored  rings  are  of  course  visible.  Let  now, 
while  the  given  section  occupies  this  position,  the  mica  plate  be  placed  upon 
it,  with  the  plane  of  its  optic  axes  (determined  beforehand,  and  the  direction 


138 


PHYSICAL    CHARACTERS    OF    MINERALS. 


marked  by  a  line  for  convenience)  making  an  angle  of  45°  with  the  vibra- 
tion-planes of  the  Xicols ;  the  black  cross  disappears  and  there  remain  only 
two  diagonally  situated  dark  spots  in  the  place  of  it.  Moreover,  the  colored 
curves  in  the  two  quadrants  with  these  spots  are  pushed  farther  away  from 
the  centre  than  the  others.  The  effect  produced  is  represented  in  f.  392 
and  f.  393.  If  the  line  joining  these  two  dark  spots  stands  at  right  angles 


392 


393 


to  the  axial  plane  of  the  mica,  the  crystal  is  positive  (f.  392),  if  this  line 
coincides  with  the  axial  plane,  the  crystal  is  negative  (f.  393).  The  explana- 
tion of  this  effect  is  not  so  simple  as  to  allow  of  being  introduced  here ;  the 
effect  of  the  mica  is  to  produce  circular  polarization  of  the  light  which  it 
transmits. 

With  both  uniaxial  and  biaxial  crystals  the  student  will  find  it  of  great  assistance  always 
to  have  at  his  side  a  good  section  of  a  positive  and  a  negative  crystal.  By  comparing  the 
phenomena  observed  in  the  section  under  examination  with  those  shown  by  crystals  of  known 
character,  he  will  often  be  saved  much  perplexity. 

For  the  investigation  of  the  absorption  phenomena  of  uniaxial  crystals 
see  p.  161. 

CIRCULAR  POLARIZATION. 

In  what  has  been  said  of  polarized  light,  in  the  preceding  pages,  it  has 
been  assumed  that  a  polarized  ray  was  one  whose  vibrations  took  place  in 
a  single  plane,  so  that  the  plane  of  polarization  at  right  angles  to  this  was  a 
fixed  plane.  Such  a  ray  is  said  to  be  linearly  polarized.  There  are  some 
nniaxial  crystals,  however,  which  have  the  power  to  rotate  the  plane  of  polari- 
zation ;  the  ray  is  said  to  be  circularly  polarized.  They  manifest  this  in  the 
phenomena  observed  when  an  axial  section  is  examined  in  the  polariscope. 

An  axial  section  of  a  uniaxial  crystal  normally  exhibits,  in  converging 
polarized  light,  a  black  cross  -with  a  series  of  concentric  colored  circles, 
f.  390,  p.  136.  If,  however,  a  section  of  quartz  be  cut  perpendicular  to  the 
axis  and  viewed  between  the  crossed  Nicols,  the  phenomena  observed  are 
different  from  these : — the  central  portion  of  the  black  cross  has  disap- 
peared, and  instead,  the  space  within  the  inner  ring  is  brilliantly  colored. 
Furthermore,  when  the  analyzing  Nicol  is  revolved,  this  color  changes 
from  blue  to  yellow  to  red,  and  it  is  found  that  in  some  cases  this 


CIRCULAR    POLARIZATION.  139 

change  is  produced  by  revolving  the  Nicol  to  the  right,  and  in  other  cases 
to  the  left.  To  distinguish  between  these  the  first  are  called  right-handed 
rotating  crystals,  and  the  others  left-handed.  The  relations  here  involved 
will  be  better  understood  if  the  quartz  section  is  viewed  in  parallel  mono- 
chromatic light.  Under  these  circumstances  a  similar  plate  of  calcite 
appears  dark  when  the  Nicols  are  crossed,  but  with  quartz  the  maximum 
darkness  is  only  obtained  when  the  analyzer  has  been  revolved  beyond  its 
first  position  a  certain  angle ;  this  angle  increasing  with  the  thickness  of 
the  section,  and  also  varying  with  the  color  of  the  light  employed. 

For  a  section  1  mm.  thick  in  red  light,  a  rotation  of  the  analyzer  of  19° 
is  required  to  produce  the  maximum  darkness.  For  yellow  light  the 
rotation  is  24°  with  a  plate  of  the  same  thickness  ;  with  blue,  32°,  and  so  on. 
The  rotation  of  the  analyzer  with  some  crystals  is  to  the  right,  with  others 
to  the  left. 

The  explanation  of  these  facts  lies  in  the  fact  stated  above,  that  the 
quartz  rotates  the  plane  of  vibration  of  the  polarized  light,  and  the  angle  of 
rotation  is  different  for  rays  of  different  wave-lengths.  Furthermore,  this 
rotation  of  the  plane  of  vibration  results  from  the  fact  that  in  quartz,  even 
in  the  direction  of  its  axis,  double  refraction  takes  place.  The  oscillations 
of  the  particles  of  ether  take  place  not  in  straight  lines  but  in  circles,  and 
they  move  in  opposite  directions  for  the  two  rays,  ordinary  and  extraor- 
dinary. 

An  axial  section  of  a  quartz  crystal  can  never  appear  dark  between 
crossed  Nicols  in  ordinary  light,  since  there  is  no  point  at  which  all  the 
colors  are  extinguished  ;  on  the  contrary,  it  appears  highly  colored.  The 
color  depends  upon  the  thickness  of  the  section,  and  is  the  same  as  that 
observed  in  the  centres  of  the  rings  in  converging  polarized  light.  If  sec- 
tions of  a  right-handed  and  left-handed  crystal  are  placed  together  in  the 
polar iscope,  the  centre  of  the  interference  figure  is  occupied  with  a  four- 
rayed  spiral  curve,  called  from  the  discoverer  Airy's  spiral.  Twins  of 
quartz  crystals  are  not  uncommon,  consisting  of  the  combination  of  right- 
and  left-handed  individual,  which  sometimes  show  the  spirals  of  Airy. 

It  is  a  remarkable  fact,  discovered  by  Herschel,  that  the  right-  or  left 
handed  optical  character  of  quartz  is  often  indicated  by  the  position  of  the 
trapezoheclral  planes  on  the  crystals.  When  a  given  trapezohedral  plane 
appears  as  a  modification  of  the  prism,  to  the  right  above  and  left  below, 
the  crystal  is  optically  right-handed  /  if  to  the  left  above  and  right  below, 
the  crystal  is  left-handed.  In  f .  394  the  plane  is,  as  last  remarked,  left  above 
and  right  below,  and  the  crystal  is  hence  left-handed.  Cinnabar  has  been 
shown  by  Des  Cloizeaux  to  possess  the  same  property  as  quartz ;  and  this  is 
true  also  of  some  artificial  salts,  also  solutions  of  sugar,  etc. 

In  twins  of  quartz,  the  component  parts  may  be  both  right-handed  or 
both  left-handed  (as  in  those  of  Dauphiny  and  the  Swiss  Alps)  ;  or  one  may 
be  of  one  kind  and  the  other  of  the  other.  Moreover,  successive  layers  of 
deposition  (made  as  the  crystal  went  on  enlarging,  and  often  exceedingly 
thin)  are  sometimes  alternately  right-  and  left-handed,  showing  a  constant 
oscillation  of  polarity  in  the  course  of  its  formation  ;  and,  when  this  is  the 
case,  and  the  layers  are  regular,  cross-sections,  examined  by  polarized  light, 
exhibit  a  division,  more  or  less  perfect,  into  sectors  of  120°,  parallel  to  the 
plane  R,  or  into  sectors  of  6u°.  If  the  layers  are  of  unequal  thickness, 


140 


PHYSICAL    CHARACTERS    OF   MINERALS. 


there  are  broad  areas  of  colors  without  sectors.     In  f.  395  (by  Des  Cloizeaux, 
from  a  crystal  from  the  Dept.  of  the  Aude),  half  of  each  sector  of  60°  is 


395 


-1 


R 


right-handed,  and  the  other  half  left  (as  shown  by  the  arrows),  and  the  dark 
radii  are  neutral  bands  produced  by  the  overlapping  of  layers  of  the  two 
kinds.  These  overlapping  portions  often  exhibit  the  phenomenon  of  Airy's 
spiral. 

C.  BIAXIAL  CRYSTALS. 

General  Optical  Character. 

As  in  the  crystalline  systems,  thus  far  considered,  so  also  in  the  anisome- 
tric  systems,  the  orthorhombic,  monoclinic,  and  triclinic,  there  is  a  strict  corre- 
spondence between  the  molecular  structure,  as  exhibited  in  the  geometrical 
form  of  the  crystals,  and  their  optical  properties.  In  the  crystals  of  these 
systems  there  is  no  longer  one  axis  around  about  which  the  elasticity  of  the 
light- ether",  that  is,  the  velocity  of  the  light,  is  everywhere  alike.  On  the 
contrary,  the  relations  are  much  less  simple,  and  less  easy  to  comprehend. 
There  are  two  directions  in  which  the  light  passes  through  the  crystal 
without  double  refraction — these  are  called  the  optic  axes,  and  hence  the 
crystals  are  biaxial — but  in  every  other  direction  a  ray  of  light  is  separated 

into  two  rays,  polarized  at  right  angles  to 
each  other.  Neither  of  these  conforms  to 
the  law  of  simple  refraction.  The  subject 
was  first  developed  theoretically  by  Fresnel, 
and  his  conclusions  have  since  been  fully 
verified  by  experiment. 

r~—A  Axes  of  elasticity.* — In  regard  to  the 
elasticity  of  the  ether  in  a  biaxial  crystal 
there  are  (1)  a  maximum  value,  (2)  a 
minimum  value,  and  (3)  a  mean  value,  and 
these  values  in  the  crystal  are  found  in 
directions  at  right  angles  to  each  other. 
In  f.  396,  CO  represents  the  axis  (c)  of  least  elasticity,  AA  of  greatest 
elasticity  (a),  and  JSJS'  of  mean  elasticity  (b).  A  ray  passing  in  the  direc- 


cf 


OPTICAL    CHARACTERS    OF    BIAXIAL    CRYSTALS. 


397 


tion  CC'  vibrates  in  a  plane  at  right  angles,  that  is,  parallel  to  BE'  and 
AA '.  Similarly  for  the  ray  BB'  the  vibrations  are  parallel  to  AA'  and 
CC' ,  and  for  the  ray  A  A'  parallel  to  BB'  and  CC'.  Between  these 
extreme  values  of  the  axes  of  elasticity,  the  elasticity  varies  according  to  a 
regular  law,  as  will  be  seen  in  the  following  discussion.  The  form  of  the 
wave-surface  for  a  biaxial  crystal  may  be  determined  by  fixing  its  form 
for  the  planes  of  the  axes  a,  b,  and  c. 

Wave-surface. — First  consider  the  case  of  rays  in  the  plane  of  the  axes 
BB'  and  CC'  (f.  397).  A  ray  pass- 
ing in  the  direction  CC'  is  separated 
into  two  sets  of  vibrations,  one  paral- 
lel to  AA' ,  corresponding  to  the 
greatest  elasticity,  moving  more 
rapidly  than  the  other  set,  parallel 
to  BB' ,  which  correspond  to  the 
mean  elasticity.  The  velocity  of  the 
two  sets  of  vibrations  are  made  pro- 
portional to  the  lengths  of  the  lines 
?mi,  and  mo  respectively,  in  f.  397. 
Again,  for  a  ray  in  the  same  plane, 
parallel  to  BB' ,  the  vibrations  are 
(1)  parallel  to  A  A',  and  propagated 
faster  (greatest  elasticity]  than  the 
other  set ;  (2)  parallel  to  CO  (least 
elasticity).  Again,  in  f.  397,  on  the 
line  CC' )  mil",  and  mq"  are  made 
proportional  to  these  two  velocities ; 
here  mn  —  mn",  and  for  a  ray  in  the 
same  plane  in  any  other  direction,  there  will  be  one  set  of  vibrations 
parallel  to  A  A',  with  the  same  velocity  as  before,  and  another  set  at  right 
angles  with  a  velocity  between  mo  and  mq",  determined  by  the  ellipse 
whose  semi-axes  are  proportional  to  the 
mean  and  greatest  axes  of  elasticity. 

Fig.  397  then  represents  the  section  of 
the  wave-surface  through  the  axes  CC' 
and  BB'.  The  circle  nn"  shows  the 
constant  velocity  for  all  vibrations  par- 
allel to  A  A ',  and  the  ellipse  the  variable 
values  of  the  velocity  for  the  other  set  of 
vibrations  at  right  angles  to  the  tirst. 

Again,  for  a  ray  in  the  plane  AA', 
BB ,  the  method  of  the  construction 
is  similar.  The  vibrations  will  in  every 
case  take  place  in  the  plane  at  right 
angles  to  the  direction  of  the  ray,  which 
plane  must  always  pass  through  the  axis 
CC'  of  least  elasticity.  Hence  for  every 
direction  of  the  ray  in  the  plane  men- 
tioned, one  set  of  vibrations  will  always 
be  parallel  to  CC' ',  and  hence  be  propagated  with  a  constant  velocity 


142 


PHYSICAL    CHARACTERS    OF   MINERALS. 


(=  mo',  f .  398),  and  hence  this  is  expressed  by  the  circle  oo' .  The  other  set 
of  vibrations  will  be  at  right  angles  to  CC' ,  and  the  velocity  with  which 
they  are  propagated  will  vary  according  as  they  are  parallel  to  AAf 
(—  mn,  f.  398),  or  parallel  to  BE'  (=  mq'},  or  some  intermediate  value  for 
an  intermediate  position.  The  section  of  the  wave-surface  is  consequently 
a  circle  within  an  ellipse. 

Finally,  let  the  ray  pass  in  some  direction  in  the  plane  CC',  A  A', of  least  and 
greatest  elasticity,  the  section  of  the  wave-surface  is  also  a  circle  and  ellipse. 

Suppose  the  ray  passes  in  the  direction 
parallel  to  AA',  the  vibrations  will  be 
(1)  parallel  to  CC,  and  (2)  parallel  to 
BB',  those  (1)  parallel  to  CC'  (least  axis 
of  elasticity)  are  propagated  more  slowly 
than  those  (2)  parallel  to  BB'  (axis  of 
mean  elasticity).  In  f.  399,  on  the  line 
A  A ',  lay  off  mo'  and  mq'  proportional  to 
these  two  values. 

Again,  for  a  ray  parallel  to  CO'  the 
vibrations  will  take  place  (1)  parallel  to 
A  A',  and  (2)  parallel  to  BB',  the  former 
will  be  propagated  with  greater  velocity 
than  those  latter.  These  two  values  of 
the  velocity  in  the  direction  CC'  are 
represented  by  mn''  and  mq"  (=  mq'). 
For  any  intermediate  position  of  the  ray 
in  the  same  plane  there  will  always  be 
one  set  of  vibrations  parallel  to  BB 
(mq'  =  mq",  f.  399,  hence  the  circle).  The  other  set  at  right  angles  to  these 

will  be  propagated  with  a  velocity  va- 
rying according  to  the  direction,  from 
that  corresponding  to  the  least  axis 
of  elasticity  (represented  by  mo' ,  f .  399), 
to  that  of  the  greatest  axis  of  elasticity 
(mn"). 

Optic  axes. — It  is  seen  that  the  cir- 
cle, representing  the  uniform  velocity 
of  vibrations  parallel  to  b,  and  the 
ellipse  representing  the  varying  value 
of  the  velocity  for  the  vibrations  at 
right  angles  to  these,  intersect  one  an- 
other at  P,  P',  f.  399.  The  obvious 
meaning  of  this  fact  is  that,  for  the 
directions  mP,  and  mP',  making 
equal  angles  with  the  axis  CO',  the 
velocity  is  the  same  for  both  sets  of 
vibrations ;  these  are  not  separated 
from  each  other,  the  ray  is  not  doubly 
refracted,  and  not  polarized. 
These  two  directions  are  called  the  OPTIC  AXES.  All  anisometric  crystals 
have,  as  has  been  stated,  two  optic  axes,  and  are  hence  called  biaxial. 


OPTICAL    CHAKACTERS    OF    BIAXIAL    CRYSTALS.  143 

The  complete  wave-surface  of  a  biaxial  crystal  is  constructed  from  the 
three  sections  given  in  f.  397,  398,  399.  It  is  shown  graphically  in  f.  400, 
where  the  lines  PP,  and  P'P'  are  the  two  optic  axes. 

bisectrices,  or  Mean-lines. — As  shown  in  f.  399,  the  optic  axes  always  lie 
in  the  plane  of  greatest  (a)  and  least  (c)  elasticity,  and  the  value  of  the  optic 
axial  angle  is  known  when  the  axes  of  elasticity  are  given  as  stated  below. 
The  axis  of  elasticity  which,  as  the  line  CC'3  f.  399,  bisects  the  acute  angle 
is  called  the  acute  bisectrix,  or  first  mean-line  (erste  Mittellinie,  Germ.),  and 
that  bisecting  the  obtuse  angle,  the  obtuse  bisectrix,  or  second  mean-line 
(zweite  Mittellinie,  Germ?). 

Positive  and  negative  crystals. — When  the  acute  bisectrix  is  the  axis  of 
least  elasticity  (c),  it  is  said  to  be  positive,  and  when  it  is  the  axis  of  greatest 
(a)  elasticity,  it  is  said  to  be  negative.  Barite  is  positive,  mica  negative. 

Indices  of  refraction. — It  has  been  seen  that  in  uniaxial  crystals  there 
are  two  extreme  values  for  the  velocity  with  which  light  is  propagated,  and 
corresponding  to  them,  and  inversely  proportional  to  them,  two  indices  of 
refraction.  Similarly  for  biaxial  crystals,  where  there  are  three  axes  of  elasti- 
city, there  are  three  indices  of  refraction — a  maximum  index  a,  a  minimum  y, 
and  a  mean  value  /3  ;  a  is  the  index  for  the  rays  propagated  at  right  angles 
to  a,  but  vibrating  parallel  to  a  ;  ft  is  the  index  for  rays  propagated  perpen- 
dicularly to  b,  by  vibrations  parallel  to  b  ;  7  is  the  index  for  rays  propagated 

perpendicularly  to  c,  but  vibrating  parallel  to  c.     a  =  -,  £  =  -,  y  =  -. 

it         b  c 

If  a,  /3,  and  y  are  known,  the  value  of  the  optic  axial  angle  (2  V)  can  be 
calculated  from  them  by  the  following  formula : 


cos  V  = 


Dispersion  of  the  optic  axes. — It  is  obvious  that  the  three  indices  of 
refraction  may  have  different  values  for  the  different  colors,  and  as  the  angle 
of  the  optic  axes,  as  explained  in  the  last  paragraph,  is  determined  by  these 
three  values,  the  axial  angle  will  also  vary  in  a  corresponding  manner. 

This  variation  in  the  value  of  the  axial  angle  for  rays  of  different  wave- 
lengths is  called  the  dispersion  of  the  axes,  and  the  two  possible  cases  are 
distinguished  by  writing  p  >  v  when  the  angle  for  the  red  rays  (p)  is  greater 
than  for  the  blue  (violet,  v),  and  p  <  v  when  the  reverse  is  true. 

In  the  properties  thus  far  mentioned,  the  three  systems  are  alike  ;  in 
details,  however,  they  differ  widely. 

Practical  Investigation  of  Biaxial  Crystals. 

Interference  figures. — A  section  cut  perpendicular  to  either  axis  will 
show,  in  converging  polarized  light,  a  system  of  concentric  rays  analogous 
to  those  of  uniaxial  crystals,  f.  390,  but  more  or  less  elliptical.  There  is, 
moreover,  no  black  cross,  but  a  single  black  line,  which  changes  its  position 
as  the  Nicols  are  revolved. 


144: 


PHYSICAL    CHARACTERS    OF    MINERALS. 


If  a  section  of  a  biaxial  crystal,  cut  perpendicularly  to  the  first,  that  IB 
acute,  bisectrix,  is  viewed  in  the  polariscope,  a  different  phenomenon  is 
observed. 

There  are  seen  in  this  case,  supposing  the  plane  of  the  axes  to  make  an  angle 
of  45°  with  the  planes  of  polarization  of  the  crossed  Nicols,  two  black  hyper- 
bolas, marking  the  position  of  the  axes,  a  series  of  elliptical  curves  surround- 
ing the  two  centres  and  finally  uniting,  forming  a  series  of  lemniscates. 
If  monochromatic  light  is  employed,  the  rings  are  alternately  light  and 
dark ;  if  white  light,  each  ring  shqws  the  successive  colors  of  the  spectrum. 
If  one  of  the  Nicol  prisms  be  revolved,  the  dark  hyperbolic  brushes  gradu- 
ally become  white,  and  the  colors  of  the  rings  take^the  complementary  tints 
after^  a  revolution  of  90°.  Since  the  black  hyperbolic  brushes  mark  the 
position  of  the  optic  axes,  the  smaller  the  axial  angle  the  nearer  together 
are  the  hyperbolas,  and  when  the  angle  is  very  small,  the  axial  figure 


observed  closely  resembles  the  simple  cross  of  a  uniaxial  crystal.  On  the 
other  hand,  when  the  axial  angle  is  large  the  hyperbolas  are  far  apart,  and 
may  even  be  so  far  apart  as  to  be  invisible  in  the  field  of  the  polariscope. 

When  the  plane  of  the  axes  coincides  with  the  plane  of  vibration  for 
either  Nicol,  these  being  crossed,  an  unsymmetrical  black  cross  is  observed, 
and  also  a  series  of  elliptical  curves.  Both  these  figures  are  well  exhibited 
on  the  plate  opposite  this  page ;  the  one  gradually  changes  into  the 
other  as  the  crystal-section  is  -revolved  in  the  horizontal  plane,  the  Nicols 
remaining  stationary. 

A  section  of  a  biaxial  crystal  cut  perpendicular  to  the  obtuse  bisectrix 
will  exhibit  the  same  figures  under  the  same  conditions  in  polarized  light, 
when  the  angle  is  not  too  large.  This  is,  however,  generally  the  case,  and 
in  consequence  the  axes  suffer  total  reflection  on  the  inner  surface  of  the 
section,  and  no  axial  figures  are  visible.  This  is  sometimes  the  case  also 


OPTICAL   CHARACTERS    OF   BIAXIAL    CRYSTALS. 


145 


with  a  section  cut  normal  to  the  acute  bisectrix,  when  the  angle  is  large. 
A  micrometer  scale  in  the  polariscope,  f.  384,  allows  of  an  approximate 
measurement  of  the  axial  angle ;  the  value  of  each  division  of  the  scale 
being  known. 

Measurement  of  the  axial  angle. — The  determination  of  the  angle  made 
by  the  optic  axes  is  of  the  highest  importance,  and  the  method  of  proce- 
dure offers  no  great  difficulties.  Fig.  401  shows  the  instrument  recom- 
mended for  this  purpose  by  DesCloizeaux ;  its  general  features  will  be 
understood  without  detailed  description  ;  some  improvements  have  been 
introduced  by  Groth,  which  make  the  instrument  more  accurate  and  con- 
venient of  use.  The  section  of  the  crystal,  cut  at  right  angles  to  the  bisec- 
trix, is  held  in  the  pincers  at  c,  with  the  plane  of  the  axes  horizontal, 
making  an  angle  of  45°  with  the  plane  of  vibration  of  the  Nicols  (NN\ 
There  is  a  cross- wire  in  the  focus  of  the  eye-piece,  and  as  the  pincers  hold- 
ing the  section  are  turned  by  the  screw  F,  one  of  the  axes,  that  is  one  black 
hyperbola,  is  brought  in  coincidence  with 
the  vertical  cross-wire,  and  then,  by  a 
further  revolution  of  F,  the  second.  The 
angle  which  the  section  has  been  turned 
from  one  axis  to  the  second,  as  read  off 
at  the  vernier  H  on  the  graduated  circle 
above,  is  the  apparent  angle  for  the  axes 
of  the  given  crystal  as  seen  in  the  air 
(oca,  f.  402).  ft  is  only  the  apparent 
angle,  for,  owing  to  the  refraction  suffered 
on  passing  from  the  section  of  the  crystal 
to  the  air,  the  true  axial  angle  is  more  01 
less  increased,  according  to  the  refractive 
index  of  the  given  crystal. 

This  being  understood,  the  fact  already 
stated  is  readily  intelligible,  that  when  the  axial  angle  exceeds  a  certain 
limit,  the  axes  will  suffer  total  reflection  (p.  124),  and  they  will  be  no  longer 
visible  at  all.  When  this  is  the  case,  oil*  or  some  other  medium  with  high 
refractive  power  is  made  use  of,  into  which  the  axes  pass  when  no  longer 
visible  in  the  air.  In  the  instrument  described  a  small  receptacle  holding 
the  oil  is  brought  between  the  tubes,  as  seen  in  the  figure,  and  the  pincers 
holding  the  section  are  immersed  in  this,  and  the  angle  measured  as  before. 

In  the  majority  of  cases  it  is  only  the  acute  axial  angle  that  it  is  practi- 
cable to  measure ;  but  sometimes,  especially  when  oil  is  made  use  of,  the 
obtuse  angle  can  also  be  determined  from  a  second  section  normal  to  the 
obtuse  bisectrix. 

If      E   =  the  apparent  semi-axial  angle  in  air  (f.  402). 
j  HO.  =  the  apparent  semi-acute  angle  in  oil. 
I H0  =    u         •'  "     obtuse     "      "    " 

Va.  =  the  real  (or  interior)  semi-acute  angle  (f.  402). 

V0  =    u     "       u         "         semi-obtuse    "      (f.  402). 

n     =  index  of  refraction  for  the  oil. 

/3    —  the  mean  refractive  index  for  the  given  crystallized  substance. 

*  Almond  oil,  which  has  been  decolorized  by  exposure  to  the  light,  is  commonly  employed. 


146  PHYSICAL    CHARACTERS    OF    MINERALS. 

sin  E  --  n  sin  Ha  ;  sin   Va  =  -  sin  fla  ;  sin  V0  =  -^  sin  R0. 

These  formulas  give  the  true  interior  angle  from  the  measured  apparent 
angle  when  the  mean  refractive  index  (/?)  is  known. 

If,  however,  it  is  possible  to  measure  both  the  acute  and  obtuse  apparent 
angles,  the  true  angle,  and  also  the  value  of  /3,  can  be  determined  from 
them.  For  sin  V0  =  cos  Va,  hence  : 

^        sin  Ha  sin  77~a  sin  H0        sin  V* 

tan  Va  —  — — jj  ;  ft  =  n  -    —^  —  n =?  =  — — ^ . 

sin  H0  sin    Va          cos    ya        sin  Ji 

In  measuring  this  an^le,  if  white  light  is  employed,  the  colors  being 
separated,  the  position  of  the  hyperbolas  is  a  little  uncertain ;  hence  it  is 
always  important  to  measure  the  angle  for  monochromatic  light,  red  and 
yellow  and  blue  particularly.  This  is  especially  essential  where  the  disper- 
sion of  the  axes  is  considerable. 

Determination  of  the  indices  of  refraction. — The  values  of  the  three 
indices  of  refraction,  a,  /?,  7,  for  biaxial  crystals,  may  be  determined  from 
three  prisms  cut  with  their  refracting  edges  parallel  respectively  to  the 
three  axes  of  elasticity  a,  b,  and  c.  In  each  case,  after  the  angle  of  the 
prism  has  been  measured,  the  angle  of  minimum  deviation  must  be  meas- 
ured for  that  one  of  the  two  refracted  rays  whose  vibrations  are  parallel 
to  the  edge  of  the  prism  ;  the  formula  of  p.  124  is  then  employed. 

It  is  possible,  however,  to  obtain  the  values  of  a,  /3,  and  7  with  two 
prisms  ;  in  this  case  one  of  the  prisms  must  be  so  made  that  its  vertical  edge 
is  parallel  to  one  axis  of  elasticity,  while  the  line  bisecting  its  refracting 
angle  at  this  edge  is  parallel  to  a  second.  In  the  case  of  such  a  prism  the 
minimum  deviation  of  the  ray  is  obtained  for  both  rays,  that  having  its 
vibrations  parallel  to  the  prism-edge,  and  that  vibrating  at  right  angles  to 
this,  that  is  parallel  to  the  bisector  of  the  prismatic  angle. 

Of  the  three  indices  of  refraction,  (3  is  one  which  it  is  most  important  to 
determine,  since  by  means  of  it,  in  accordance  with  the  above  formulas, 
the  true  value  of  the  axial  angle  can  be  calculated  from  its  apparent  value 
in  air.  The  prism  to  give  the  value  of  /3  should  obviously  have  its  refract- 
ing edge  parallel  to  the  mean  axis  of  elasticity  b,  that  is  at  right  angles  to 
the  plane  of  the  optic  axes. 

Determination  of  the  positive  or  negative  character  of  biaxial  crystals. 
—The  question  of  the  positive  or  negative  character  of  a  biaxial  crystal  is 
determined  from  the  values  of  the  indices  of  refraction,  where  these  can  be 
obtained.  If  c,  the  axis  of  least  elasticity,  is  the  acute  bisectrix,  the  crystal 
is  optically  positive  ;  if  a,  the  axis  of  greatest  elasticity,  is  the  acute  bisec- 
trix, the  crystal  is  optically  negative  •  in  the  former  case  the  value  of  b  is 
nearer  that  of  c  than  of  a,  in  the  second  case  the  reverse  of  this  is  true. 

There  is,  however,  a  more  simple  method  of  solving  the  problem,  as  was 
remarked  also  in  regard  to  uniaxial  crystals.  The  methods  are  similar. 

The  quarter-undulation  mica  plate  may  be  employed  just  as  with'  uniaxial 
crystals,  but  its  use  is  not  very  satisfactory  excepting  when  the  axial  diver- 
gence is  quite  small.  In  this  case  it  can  be  employed  to  advantage,  the 


DISTINGUISHING    OPTICAL   CHARACTERS    OF    ORTHORHOMBIC   CRYSTALS.       147 

plane  of  the  axes  of  the  crystal  investigated  being  made  to  coincide  with 
the  vibration-plane  of  one  of  the  Nicols.  The  more  general'  method  is  the 
employment  of  a  wedge-shaped  piece  of  quartz  ;  this  is  so  cut  that  one  sur- 
face coincides  with  the  direction  of  the  vertical  axis,  and  the  other  makes 
an  angle  of  4°  to  6°  with  it.  By  this  means  a  section  of  varying  thickness  is 
obtained.  The  section  to  be  examined  normal  to  .the  acute  bisectrix  is 
brought  between  the  crossed  Nicols  of  the  polariscope  (f.  384),  and  with  its 
axial  plane  making  an  angle  of  45°  with  the  polarization-plane  of  the 
Nicol  prisms  ;  that  is,  so  that  the  black  hyperbolas  are  visible.  The  quartz 
wedge  is  now  introduced  slowly  between  the  section  examined  and  the 
analyzer ;  in  the  instrument  figured  a  slit  above  gives  an  opportunity  to 
insert  it.  The  quartz  section  is  introduced  first,  in  a  direction  at  right 
angles  to  the  axial  plane,  that  is,  to  the  line  joining  the  hyperbolas,  of  the 
plate  investigated  ;  and  second,  parallel  to  the  axial  plane,  that  is,  in  the 
direction  of  the  line  joining  the  hyperbolas.  In  one  direction  or  the  other 
it  will  be  seen,  when  the  proper  thickness  of  the  quartz  wedge  is  reached, 
that  the  central  rings  appear  to  increase  in  diameter,  at  the  same  time 
advancing  from  the  centre  to  the  extremities. 

The  effect,  in  other  words,  is  that  which  would  have  been  produced  by 
the  thinning  of  the  given  section.  If  the  phenomenon  is  observed  in  the 
first  case  when  the  axis  of  the  quartz  is  parallel  to  the  axial  plane,  that  is 
to  the  obtuse  bisectrix,  it  shows  that  this  bisectrix  must  have  an  opposite 
sign  to  the  quartz,  that  is,  the  obtuse  bisectrix  is  negative,  and  the  acute 
bisectrix  positive.  If  the  mentioned  change  in  the  interference  figures 
takes  place  when  the  axis  of  the  quartz  is  at  right  angles  to  the  axial  plane, 
then  obviously  the  opposite  must  be  true  and  the  acute  bisectrix  is  negative. 

The  same  effect  may  be  obtained  by  bringing  an  ordinary  quartz  section 
of  greater  or  less  thickness,  cut  normal  to  the  axis,  between  the  analyzer  and 
the  crystal  examined,  and  then  inclining  it,  first  in  the  direction  of  the 
axial  plane,  and  again  at  right  angles  to  it.  The  method  of  investigation 
with  the  quartz  wedge  can  be  applied  even  in  those  cases  where  the  axial 
angle  is  too  large  to  appear  in  the  air. 

For  the  investigation  of  the  absorption  phenomena  of  biaxial  crystals, 
see  p.  161. 

DISTINGUISHING  OPTICAL  CHARACTERS  OF  ORTHORHOMBIC  CRYSTALS. 

In  the  OrthorhombHc  System,  in  accordance  with  the  symmetry  of  the 
crystallization,  the  three  axes  of  elasticity  coincide  with  the  three  crystallo- 
graphic  axes.  Further  than  this,  there  is  no  immediate  relation  between 
the  two  sets  of  axes  in  respect  to  magnitude,  for  the  reason  that,  as  has  been 
stated,  the  choice  of  the  crystallographic  axes  is  arbitrary,  and  has  been 
made,  in  most  cases,  without  reference  to  the  optical  character. 

Schrauf  has  proposed  that  the  crystallographic  vertical  axis  (c)  should  be 
always  made  to  coincide  with  the  acute  bisectrix,  which  would  be  very 
desirable,  especially,  as  urged  by  him,  in  showing  the  true  relations  between 
the  orthorhombic  and  hexagonal  systems.  Of  course,  this  suggestion  can 
be. carried  out  only  in  those  species  in  which  the  optical  character  is  known. 

Schrauf  (Phys.  Min.,  p.  302,  303)  has  shown  there  is  a  close  analogy  between  certain 


148  PHYSICAL    CHARACTERS    OF   MINERALS. 

orthorhombic  crystals  whose  prismatic  angle  is  near  120°  (compare  remarks  on  twins,  p.  96) 
and  the  crystals  of  the  hexagonal  system.  With  these  the  acute  bisectrix  is  uniformly  parallel 
to  the  prismatic  edge,  and  normal  to  the  six-sided  basal  plane,  analogous  to  the  one  optic  axis  of 
true  hexagonal  forms.  Moreover,  he  shows  that  the  nearer  the  prismatic  angle  approaches 
120°,  the  less  the  difference  between  the  three  axes  of  elasticity,  and  the  nearer  the  approach 
to  the  uniaxial  character. 

By  the  combination  of  thin  plates  of  a  biaxial  mica  optical  phenomena  may,  under  some 
conditions,  be  observed  in  polarized  light  which  are  similar  to  those  shown  by  uniaxial  crys- 
tals. Similarly  twins  of  chrysoberyl  (p.  97)  have  been  described  which  in  spots  gave  the 
axial  image  of  uniaxial  crystals.  This  subject  has  been  investigated  by  Reusch  (Pogg. 
cxxxvi.,  626,  637,  1869),  and  later  by  Cooke  (Am.  Acad.  Set,  Boston,  p,  35,  1874). 

Practical  Optical  Investigation  of  Orthorhombic  Crystals. 

Determination  of  the  plane  of  the  optic  axes. — The  position  of  the 
three  axes  of  elasticity  in  an  orthorhombic  crystal  is  always  known,  since 
they  must  coincide  with  the  crystallographic  axes  ;  but  the  plane  of  the  optic. 
axes,  that  is,  of  the  axes  of  greatest  (a)  and  least  (c)  elasticity,  must  in  each 
case  be  determined.  This  plane  will  be  parallel  to  one  of  the  three  diame- 
tral or  pinacoid  planes.  In  order  to  determine  in  which  the  axes  lie,  it  is 
necessary  to  cut  sections  parallel  to  these  three  directions  ;  one  of  these  three 
sections  will  in  all  ordinary  cases  show,  in  converging  polarized  light,  the 
interference  figures  peculiar  to  biaxial  crystals.  It  is  evident,  too,  that  two 
of  the  three  sections  named  determine  the  character  of  the  third,  so  that 
the  plane  of  the  optic  axes  and  the  position  of  the  acute  bisectrix  can  be  in 
practice  generally  told  from  them. 

Measurement  of  the  axial  angle,,  p  ^  v. — From  the  section  showing  the 
axial  figures,  that  is,  normal  to  the  acute  bisectrix,  the  axial  angle  can  be 
measured  in  the  manner  which  has  been  described  (p.  145).  If  it  is  prac- 
ticable to  determine  also  the  obtuse  axial  angle,  from  a  second  section  nor- 
mal to  the  obtuse  bisectrix,  it  will  be  possible  to  calculate  the  true  axial 
angle  from  these  data,  and  also  the  mean  index  of  refraction  (/3). 

There  is  further  to  be  determined  the  dispersion  of  the  axes.     Whether 

the  axial  angle  for  red  rays  is  greater  or 
403  less  than  for  blue  (p  >  v,  or  p  <  v)  can  be 

seen  immediately  from  the  figure  of  the 
.?''  axes,  as  in  f.  1#,  13,  in  the  colored   plate, 

'  p.  144.     It  is  obviously  true  in  this  case, 

from  f .  l<z,  as  also  f .  13,  that  the  angle  for 
the  blue  rays  is  greater  than  that  for  the 
red  (p  <  v),  and  so  in  general.  This  same 

B2 ^n^..Q. B*     point   is  also   accurately  determined,   of 

course,  by  the  measured  angle  for  the  two 
monochromatic  colors. 

In  all  cases  the  same  line  will  be  the 
'*  bisectrix  of  the  axial  angle  for  both  blue 
and  red  rays,  so  that  the  position  of  the 
respective  axes  is  symmetrical  with  refer- 
ence to  the  bisectrix.  In  f.  403,  the  dis- 
persion of  the  axes  is  illustrated,  where  p  <  v ;  it  is  shown  also  that  the 
lines,  &  J?1  and  J?2.B2,  bisect,  the  angles  of  both  red  (pOp)  and  blue 
(vOv')  rays.  It  also  needs  no  further  explanation  that  fora  certain  relation 


DISTINGUISHING    OPTICAL    CHARACTERS    OF   MONOCLINIC    CRYSTALS.          149 

of  the  refractive  indices  of  the  different  colors,  the  acute  bi&ectrix  of  the 
axial  angle  for  red  rays  may  be  the  obtuse  bisectrix  for  the  angle  for  blue 
rays. 

Indices  of  refraction,  etc. — The  determination  of  the  indices  of  refrac- 
tion and  the  character  (+  or  — )  of  the  acute  bisectrix  is  made  for  ortho- 
rhombic  crystals  in  the  same  way  as  for  all  biaxial  crystals  (p.  146).  It  is 
merely  to  be  mentioned  that,  since  the  axes  of  elasticity  always  coincide 
with  the  crystallographic  axes,  it  will  happen  not  infrequently  that  crystals 
without  artificial  preparation  will  furnish,  in  their  prismatic  or  dome  series, 
prisms  whose  edges  are  parallel  to  the  axes  of  elasticity,  and  consequently 
at  once  suitable  for  the  determination  of  the  indices  of  refraction. 


DISTINGUISHING  OPTICAL  CHARACTERS  OF  MONO-CLINIC  CRYSTALS. 

Position,  of  the  axes  of  elasticity. — In  crystals  belonging  to  the  mono- 
clinic  system  one  of  the  axes  of  elasticity  always  coincides  with  the  ortho- 
diagonal  axis  b,  and  the  other  two  lie  in  the  plane  of  symmetry  at  right 
angles  to  this  axis.  Here  obviously  three  cases  are  possible,  according 
to  which  two  of  the  axes,  a,  b,  or  c,  lie  in  the  plane  of  symmetry. 

Corresponding  to  these  three  positions  of  the  axes  of  elasticity,  there  may 
occur  three  kinds  of  dispersion  of  these  axes,  or  dispersion  of  the  bisectrices. 
This  dispersion  arises  from  the  fact  that,  while  the  position  of  one  axis  of 
elasticity  is  always  fixed,  the  position  of  the  other  two  is  indeterminate  and 
for  the  same  crystal  may  be  different  for  the  different  colors,  so  that  the 
bisectrices  of  the  different  colors  may  not  coincide. 

Dispersion  of  the  bisectrices. — 1.  The  bisectrices,  that  is,  the  axes  of 
greatest  and  least  elasticity,  lie  in  the  plane  of  sym- 
metry, while  the  orthodiagonal  axis  b  coincides  with  b. 
The  optic  axes  here  suffer  a  dispersion  in  this  plane 
of  symmetry,  and,  as  already  stated,  they  do  not  lie 
symmetrically  with  reference  to  the  acute  bisectrix. 
This  is  illustrated  in  f.  404,  where  MM  is  the  bisec- 
trix for  the  angle,  vOv',  and  BB  for  the  angle  pOp'. 
This  kind  of  dispersion  is  called  by  DesCloizeaux 
inclined  (dispersion  inclinee). 

2.  The  second  case  is  that  where  the  plane  of  the 
optic  axes  is  perpendicular  to  the  plane  of  symmetry, 
and  the  acute  bisectrix  stands  at  right  angles  to  the 
orthodiagonal   axis   b.      In   other   words,    the   acute 
bisectrix  and  the  axis  of  mean  elasticity  both  lie  in 
the  plane  of  symmetry.     In  this  case  also  dispersion 
of  the  axes  may  take  place,  and  in  this  way — the 

plane  of 'the  optic  axes  for  all  the  colors  lies  parallel  to  the  orthodiagonal, 
but  these  planes  may  have  different  inclinations  to  the  vertical  axis.  This 
is  called  horizontal  dispersion  by  DesCloizeaux. 

3.  Still  again,  in  the  third  place,  the  plane  of  the  optic  axes  lies  perpen- 
dicular to  the  plane  of  symmetry  ;   but  in  this  case  the  acute  bisectrix  is 
parallel  to  the  crystallographic  axis  b,  so  that  the  obtuse  bisectrix  and  axis 
of  mean  elasticity  lie  in  the  plane  of  symmetry.     The  dispersion  which 


150 


PHYSICAL    CHARACTEKS    OF   MINERALS. 


results  in  this  case  is  called  by  DesCloizeaux  crossed  (dispersion  tournante, 
or  croisee). 

Dispersion  as  shown  in  the  interference  figures. — If  an  axial  section 
of  a  monoclinic  crystal  be  examined  in  converging  polarized  light,  the  kind 
of  dispersion  which  characterizes  it  will  be  indicated  by  the  nature  of  the 
interference  figures  observed ;  the  three  cases  are  illustrated  by  the  figures 
upon  the  accompanying  plate,  taken  from  DesCloizeaux  (p  144). 

Figs.  \a,  15  represent  the  interference  figures  for  an  orthorhombic  crystal 
(nitre),  characterized  by  the  symmetry  in  the  size  of  the  rings,  and  the 
distribution  of  the  colors.  Figs.  2a,  25  (diopside),  3$,  35  (orthoclase),  4$,  45 
(borax),  are  examples  of  the  corresponding  figures  for  monoclinic  crystals, 
characterized  as  such  more  or  less  distinctly  by  the  want  of  symmetry  in 
the  size  of  the  rings  about  the  two  axes,  and  the  irregularity  in  the  arrange- 
ment of  the  colors. 

(1)  Inclined  dispersion. — Where  the  axes  are  not  symmetrically  situated 
with  reference  to  the  acute  bisectrix.  The  relation  of  the  two  axial  figures 
is  illustrated  by  f.  405.  In  f.  20,  25  this  kind  of  dispersion  is  indicated  by 

405 


the  position  of  the  red  and  blue  at  the  centres  of  the  rings,  and  on  the 
borders  of  the  hyperbolas,  compare  f.  la,  15  of  the  normal  figure,  where 
there  is  no  dispersion  of  the  bisectrices. 

(2)  Horizontal  dispersion,  where  the  planes  of  the  optic  axes  for  the 
different  colors  make  different  angles  with  the  axis. — This  is  illustrated  by 
f.  406.     The  effect  upon  the  interference  figures  is  seen  in  f.  3#,  3b  of  the 
plate,  by  comparing  the  colors  within  the  rings  (f.  3a),  and  on  the  borders 
of  the  hyperbolas  (f.  35),  with  f.  1«,  Ib. 

(3)  Crossed  dispersion,  where  the   acute   bisectrix   coincides   with   the 
crystallographic  axis  b. — This  is  illustrated  in  f.  407,  and  the  interference 
figures  belonging  to  this  kind  of  dispersion  are  seen  in  f.  4$,  45  of  the  plate, 
compared  as  before  with  1$,  15,  and  with  the  other  figures. 


Practical  Optical  Investigation  of  Monoclinic  Crystals. 

Determination  of  the  position  of  the  axes  of  elasticity,  that  is,  the  direc- 
tions of  vibration.  Stauroscope. — The  position  of  one  axis  of  elasticity  is 
alone  known,  since,  as  has  been  stated,  it  coincides  with  the  crystallographic 
axis  5.  In  order  to  determine  the  position  of  the  other  axes  in  the  plane  of 
symmetry,  where  they  necessarily  lie,  use  is  made  of  an  instrument,  first 
proposed  by  von  Kobell,  called  the  STAUROSCOPE.  The  principle  of  this 
instrument 'is  very  simple.  Suppose  that  the  two  Nicols  in  the  polari- 
scope  (f.  385)  have  their  planes  of  polarization  crossed,  causing  the  maxi- 
mum extinction  of  light.  Now,  if  a  section  of  any  biaxial  crystal  is  brought 


DISTINGUISHING   OPTICAL   CHARACTERS    OF   MONOCLES!  1C   CRYSTALS.         151 

between  them,  obviously,  if  the  position  of  its  two  rectangular  axes  of 
elasticity,  which  are  its  two  directions  of  vibration,  coincide  with  those  of 
the  two  Nicols,  it  will  produce  no  change  in  appearance  ;  the  field  of  the 
polariscope,  which  was  dark  before,  remains  dark.  But  suppose,  on  the 
other  hand,  that  it  is  placed  in  any  other  position  in  the  plane,  so  that  its 
two  rectangular  directions  of  vibration  do  not  coincide  with  those  of  the 
Nicols,  the  field  is  no  longer  dark,  but  more  or  less  light.  The  reason  for 
this  is,  that  the  light  from  the  lower  Nicol  meeting  the  crystal  plate  is 
separated,  according  to  the  law  of  the  parallelogram  of  forces,  into  two  sets 
of  vibrations,  which  are  again  resolved  by  the  analyzing  Nicol,  and  only  one 
set  extinguished  by  it.  If,  however,  the  plate  be  gradually  changed  in  posi- 
tion, that  is,  revolved  horizontally,  until  its  vibration-directions  (axes  of 
elasticity)  coincide  with  those  of  the  Nicols,  then,  as  at  first,  the  light  is  ex- 
tinguished. If  the  angle  is  measured  which  it  is  necessary  to  revolve  the 
section  to  accomplish  the  result  just  remarked,  that  will  be  the  angle  be- 
tween the  direction  of  one  of  the  axes  of  elasticity  of  the  plate  in  its  original 
position  and  the  vibration-plane  of  the  Nicol. 

In  figure  408,  let  the  two  larger  rectangular  arrows  represent  the  vibration- 
directions  for  the  two  Nicols,  and  between  the  two 
prisms  suppose  a  section  of  a  moiioclinic  crystal,  408 

abed,  to  be  placed  so  that  one  edge  of  a  known  crys- 
tallographic  plane  (eg.,  i-i)  coincides  with  one  of 
these  lines.  The  field  of  the  microscope,  dark  before, 
since  the  prisms  were  crossed,  is  no  longer  so,  and 
becomes  dark  again,  as  explained,  only  when  the 
crystal  is  revolved  so  that  its  vibration-directions 
(the  smaller  dotted  arrows)  coincide  with  those  of  ,«{ 
the  Nicols,  which  is  indicated  by  the  maximum 
extinction  of  the  light.  The  crystal  has  then  the 
position  a'b'c'd'.  The  angle  (I.  408),  which  it 
has  been  necessary  to  revolve  the  plate  to  obtain 
the  effect  described,  is  the  angle  which  one  of  the  axes  of  elasticity  in  the 
given  plate  makes  with  the  given  crystallographic  edge  i-i. 

The  preceding  explanations  cover  everything  that  is  essential  in  the 
Stauroscope ;  but  a  variety  of  improvements  have  been  introduced,  which 
practically  make  the  measurements  by  means  of  the  instrument  much  more 
easy  and  accurate. 

It  will  be  seen  that  the  most  important  feature  is  the  point  where  the 
maximum  extinction  of  the  light  occurs  ;  this,  however,  is  not  easy  for  the 
eye  to  decide  upon,  and  if  the  trial  is  made,  it  will  be  found  that  the  change 
produced  by  a  revolution  of  several  degrees  is  hardly  perceptible.  To 
overcome  this  difficulty,  von  Kobell  proposed  to  introduce  a  section  of  cal- 
cite  just  below  the  analyzer,  because  its  interference  figure  gives  a  better 
opportunity  to  judge  of  a  change  in  the  intensity  of  the  light.  A  still  better 
plan  is  to  introduce  a  composition  plate  of  calcite,  as  proposed  by  Brezina, 
giving  a  peculiar  interference  figure,  a  very  slight  change  in  which  destroys 
its  symmetry,  and  it  takes  its  normal  form  only  when  the  planes  of  polariza- 
tion of  the  two  Nicols  are  exactly  at  right  angles.  Supposing  this  to  be  the 
case,  when  the  crystal  has  been  introduced  the  interference  figure  is  disturbed, 
it  returns  to  its  normal  appearance  only  when  the  crystal  has  been  revolved 


152 


PHYSICAL    CHARACTERS    OF   MINERALS. 


to  the  point  where  the  vibration  -directions  of  the  Nicols  and  crystal  section 
exactly  coincide. 

It  will  be  observed  again,  that  it  is  essential  that  the  direction  of  the 
known  edge  of  the  crystal  should  be  exactly  parallel  to  the  vibration-direc- 
tion of  one  of  the  Nicols.  This  condition,  in  the  case  of  small  crystals 
especially,  is  hard  to  fulfil,  and  to  accomplish  it  most  satisfactorily  Groth 
has  proposed  to  use  the  plate  shown  in  f.  409. 

The  plate  of  glass,  v,  held  in  its  present  position  by  the  spring,  has  one 
edge  polished,  which  adjoins  u,  and  the  direction 
of  this  is  made  to  coincide  exactly  with  the  line 
joining  the  opposite  zero  points  of  the  gradua- 
tion. The  crystal  section  is  attached  to  this  plate 
over  the  hole  seen  in  -y,  and  with  a  plane  o£ 
known  crystallographic  position,  either  O,  i-l  or 
a  plane  in  that  zone  or  a  corresponding  edge, 
coinciding  with  the  direction  of  the  polished  edge 
of  the  plate.  Whether  this  coincidence  is  exact 
can  be  tested  by  the  reflective  goniometer.  In 
order  to  eliminate  any  small  error,  Groth  pro- 
poses to  measure  the  divergence  from  the  exact 
coincidence,  and  then  to  make  a  corresponding 
correction,  for  which  he  furnishes  a  series  of  tables. 

After  the  adjustment  of  the  crystal  section  on  the  plate,  the  latter  is 
inserted  in  its  place,  the  whole  plate,  I,  &,  occupying  the  position  indicated 
in  f.  385,  and  the  Nicols  so  adjusted  that  the  plane  of  vibration  of  one 
coincides  with  the  line  0°  to  180°.  The  angle  of  revolution  of  the  plate,  I, 
is  obtained  from  the  graduated  scale  on  &. 

It  is  not  always  easy  to  make  the  adjustment  of  the  IsTicols  alluded  to, 
but  the  error  arising  when  the  vibration-plane  of  the  Nicol  does  not  coincide 
with  the  line  0°  to  180°  is  easily  eliminated.  This  is  accomplished  by  remov- 
ing the  plate  v,  and,  without  disturbing  the  crystal  section,  restoring  it  to 
its  place  in  an  inverted  position.  The  measured  angle,  if  before  too  great, 
will  now  be  as  much  too  small,  and  the  arithmetical  mean  of  the  two 
measurements  will  be  the  true  angle. 

Reference  further  may  be  made  to  Groth,  Fogg.  Ann.,  cxliv.,  34,  1871. 
Determination  of  the  plane  of  the  optic  axes. — The  investigation  of  a 
section  of  a  monoclinic  crystal  parallel  to  the  plane  of  symmetry  determines 
the  position  of  the  two  remaining  axes  of  elasticity,  but  it  does  not  fix  the 
relative  position  of  the  greatest  and  least  axes  of  elasticity,  that  is,  the  plane 
of  the  optic  axes.  To  solve  the  latter  point,  sections  normal  to  each  of  the 
three  axes  must  be  examined  in  converging  polarized  light,  and  one  of 
them  will  show  the  characteristic  interference  figures.  The  section  parallel 
to  the  plane  of  symmetry  is  first  to  be  examined,  and  if  it  does  not  show 
the  axes  even  in  oil,  one  or  both  of  the  other  sections  spoken  of  must  be 
employed. 

Axial  angle,  dispersion,  etc. — The  method  of  measuring  the  axial  angle 
has  been  already  explained,  and  if  this  is  determined  for  the  different  colors 
it  will  determine  the  dispersion  of  the  axes  p  "§.  v. 

The  dispersion  of  the  axes  of  elasticity  has  been  shown  to  be  always 
indicated  by  the  character  of  interference  figures  ;  its  amount,  where  con- 


EFFECT   OF   HEAT   UPON    THE    OPTICAL    CHARACTERS    OF    CRYSTALS.         153 

siderable,  may  be  determined  by  making  the  stauroscopic  measurements  for 
different  colors. 

The  remaining  points  to  be  investigated,  the  indices  of  refraction,  and 
the  -f  or  —  character  of  the  crystal,  need  no  further  explanation  beyond 
that  which  has  been  given,  pp.  146,  147. 

DISTINGUISHING  OPTICAL  CHARACTERS  OF  TRICLINIC  CRYSTALS. 

The  crystals  of  the  triclinic  system  are  characterized  by  their  entire  want 
of  cry  stall  ographic  symmetry,  the  position  and  inclination  of  the  axes  being 
entirely  arbitrary,  and  it  follows  from  this  that  there  is  no  necessary  connec- 
tion between  them  and  the  rectangular  axes  of  elasticity.  More  than  one  of 
the  three  kinds  of  dispersion  mentioned  on  p.  150  may  occur  in  a  single 
crystal,  and  the  interference  figures  will  indicate  the  existence  of  both. 

The  practical  investigation  of  triclinic  crystals  optically  involves  great 
difficulty ;  in  general  a  series  of  successive  trials  are  required  to  determine 
the  position  of  the  axes  of  elasticity.  When  these  are  found,  the  axial  sec- 
tions can  be  prepared  and  the  axial  angle  determined,  and  the  other  points 
settled  as  with  other  biaxial  crystals. 

EFFECT  OF  HEAT  UPON  THE  OPTICAL  CHARACTERS  OF  CRYSTALS. 

In  addition  to  the  ordinary  investigation  of  crystal-sections  in  the  polari- 
scope,  it  is  often  important  to  determine  the  influence  of  heat  upon  the 
optical  character  of  crystals.  The  axial  angle  may  be  measured  at  any 
required  temperature  by  the  use  of  a  metal  air-bath.  This  is  placed  at  6y, 
(f.  401),  and  extends  beyond  the  instrument  on  either  side,  so  as  to  allow 
of  its  being  heated  with  gas  burners ;  a  thermometer  inserted  in  the  bath 
makes  it  possible  to  regulate  the  temperature  as  may  be  desired.  This  bath 
has  two  openings,  closed  with  glass  plates,  corresponding  to  the  two  tubes 
carrying  the  lenses,  and  the  crystal-section,  held  as  usual  in  the  pincers,  is 
seen  through  these  glass  windows. 

The  conclusions  of  DesCloizeaux  (see  Literature)  as  to  the  influence  of 
heat  upon  the  optical  characters  of  crystals  are  as  follows : 

(1)  [fniaxial  crystals  appear  to  be  uninfluenced  by  a  heating  of  from  10° 
to  190°  C.  (2)  .Biaxial  crystals  of  the  orthorhombic  system  suffer  a  greater 
or  less  change  in  axial  angle.  (3)  Biaxial  crystals  of  the  monodinic  system 
suffer  a  change  in  axial  angle,  and  in  addition  also  in  the  plane  of  the  axes 
when  it  is  not  the  plane  of  symmetry.  Triclinic  crystals  also  show  a  little 
change  in  the  position  of  the  axes. 

A  striking  example  of  the  change  in  axial  divergence  is  furnished  by 
gypsum.  At  ordinary  temperatures  the  axes  lie  in  the  plane  of  symmetry 
(i-l) ;  at  80°  C.  they  unite  in  a  line  making  an  angle  of  37°  28'  with  a  normal 
to  O ;  and  with  an  increased  temperature  they  again  separate  in  a  plane 
perpendicular  to  i-\.  DesCloizeaux  found  that  the  feldspars,  when  heated 
up  to  a  certain  point,  suffer  a  change  in  the  position  of  the  axes,  and  if  the 
heat  becomes  greater  and  is  long  continued,  they  do  not  return  again  to  their 
original  position,  but  remain  altered.  Weiss'*  has  made  use  of  this  principle 

*  Zur  Kenntniss  der  Feldspathbildung ;  Haarlem  Soc.  Verhandl.,  xxv.,  1866. 


154:  PHYSICAL    CHARACTERS    OF    MINERALS. 

to  determine  at  what  temperature  certain  feldspathic  rocks  were  formed. 
This  constant  change  of  axial  angle  upon  heating  is  true  also  of  brookite, 
zoisite,  and  other  minerals.  The  investigations  of  Pfaff  show  that  the  opti- 
cal properties  of  some  uniaxial  crystals  also  are  affected  by  heating,  though 
to  no  great  extent.  Pogg.,  cxxiii.,  179,  cxxiv.,  448,  etc. 


ANOMALIES  EXHIBITED  BY  SOME  CRYSTALS  IN  THEIR  OPTICAL  PHENOMENA. 

There  are  a  considerable  number  of  crystals  of  the  three  classes,  which, 
from  a  variety  of  causes,  exhibit  irregularities  in  their  optical  characters ; 
some  of  the  more  important  cases  are  mentioned  here. 

Isometric  crystals. — Boracite,  and  also  senarmontite,  sometimes  exhibit 
interference  ligures  resembling  closely  those  of  biaxial  crystals.  In  the 
case  of  boracite  this  is  explained  by  DesGloizeaux  as  due  to  the  presence 
of  enclosed  crystals  of  parasite  formed  by  alteration.  Perofskite  is  also 
strongly  doubly  refracting,  and  in  polarized  light  appears  to  be  biaxial, 
although,  as  shown  by  Kokscharow,  it  is  isometric  in  crystallographic  rela- 
tions. The  irregularities  are  supposed  by  him  to  be  caused  by  the  want  of 
homogeneity  in  the  internal  structure  of  the  crystals. 

The  properties  of  double  refraction  possessed  by  some  substances,  crystal- 
lized and  non-crystallized,  which  are  normally  isotrope,  are  explained  by 
Biot*  to  be  due  to  lamellar  polarization.  This  is  analogous  to  the  produc- 
tion of  polarized  light  by  means  of  a  series  of  thin  plates  (see  p.  128). 
Alum  crystals  have  often  the  lamellar  structure,  which  causes  these  pheno- 
mena. 

Analcite  and  leucite  have  been  included  in  the  list  of  isometric  crystals, 
which  exhibit  anomalous  optical  characters ;  but  the  most  accurate  crystal- 
lographic determination  has  referred  both  species  to  the  tetragonal  system. 
Tension  or  compression  at  the  time  of  crystallization  may  cause  isotropic 
crystals  to  polarize  light ;  Schrauf  has  described  a  uniaxial  diamond,  and 
it  was  long  since  shown  by  Brewster  that  some  diamonds  give  evidence  in 
polarized  light  of  compression  about  interior  cavities. 

Uniaxial  crystals. — A  want  of  homogeneity  in  the  crystals,  as  shown  by 
DesCloizeaux,  may  cause  uniaxial  crystals  to  exhibit  in  polarized  light  a 
variety  of  abnormal  phenomena.  In  some  cases  the  axial  figures  resemble 
those  of  biaxial  crystals,  the  cross  in  the  middle  of  the  field  (f.  390)  not 
being  closed,  but  separated  into  two  hyperbolas,  lying  near  each  other. 
Beryl,  zircon,  vesuvianite,  and  apatite  are  examples.  That  such  crystals 
are  nevertheless  uniaxial  is  proved  by  the  fact  that  the  opening  of  the  cross 
is  independent  of  the  position  of  the  Nicols,  and  is  not  altered  if  the  section 
is  turned  in  a  horizontal  plane.  If  this  is  not  true,  or  if,  when  the  section 
is  heated  (p.  153)  the  distance  between  the  hyberbolas  is  altered,  it  is  a 
proof  that  the  irregularity  is  not  due  to  lamellar  polarization,  but  that  the 
two  indices  of  refraction  are  not  exactly  equal,  and  consequently  that  the 
crystal  is  riot  strictly  uniaxial.  In  such  cases  a  revision  of  the  crystallo- 
graphical  elements  is  desirable. 

The  axial  figure  shown  by  a  section  of  apophyllite  is  peculiar,  exhibiting 

*  Biot,  Recherches  sur  la  polarisation  lamellaire,  C.  R.,  xii.,  741,  803,  871,  967. 


ANOMALIES    EXHIBITED   BY    SOME   CRYSTALS   IN    OPTICAL   PHENOMENA.         155 

a  series  of  rings  alternately  dark  violet,  and  yellow.  The  explanation  is 
found  in  the  fact  previously  stated,  that  it  is  positive  for  red  rays,  negative 
for  blue,  and  does  not  doubly  refract  yellow  light. 

Among  biaxial  crystals  irregularities  in  the  optical  phenomena  are  often 
observed.  They  are  due  in  part  to  want  of  homogeneity,  in  part  to  twin 
structure,  and  also  to  other  causes.  In  brookite  the  planes  of  the  axes  for 
red  and  blue  rays  are  at  right  angles  to  each  other,  and  hence  the  axial 
figures  vary  much  from  those  normally  observed ;  in  titanite  the  axial  angle 
for  the  two  colors  is  widely  different,  and  this  also  gives  rise  to  an  axial 
figure  of  abnormal  appearance. 

Irregular  structure,  due  to  twinning,  is  a  frequent  cause  of  peculiar  opti- 
cal phenomena  ;  crystals,  in  external  form  apparently  simple,  often  show 
themselves  to  be  made  up  of  irregular  banded  layers  in  twinned  position, 
when  examined  in  polarized  light ;  this  is  true  of  many  minerals. 

In  some  crystals,  as  occasionally  in  the  epidote  from  the  Untersulzbach- 
thal  in  the  Tyrol,  the  biaxial  figures  may  be  observed  immediately,  without 
the  use  of  the  polariscope.  This  is  due  to  the  complex  twinned  structure 
of  the  crystal,  a  thin  lamella  in  reverse  position  being  enclosed  in  the 
interior,  so  that  the  parts  of  the  crystal  on  either  side  act  as  polarizer  and 
analyzer. 


Practical  Suggestions  in  regard  to  the  Preparation  and  use  of  Crystal  Sections  made  for 

Optical  Examination. 

The  most  important  task  is  the  preparation  of  a  plate  for  examination  in  the  Stauroscope, 
or  for  the  observation  of  the  axial  interference-figures.  In  this  we  are  often  assisted  by  the 
cleavage,  which  sometimes  makes  it  possible  to  obtain  the  require  I  section  without  the  labor 
of  cutting  it.  This  is  conspicuously  the  case  with  mica  ;  also  with  topaz  and  anhydrite,  and 
other  minerals.  Sometimes  the  natural  surfaces  need  to  be  made  smooth  and  polished. 
Furthermore  natural  crystals  sometimes  occur  in  a  tabular  form,  thin  and  transparent  enough 
to  answer  the  purpose ;  this  is  true  of  the  crystals  of  wulfenite  from  Utah.  In  most  cases, 
however,  the  section  must  be  actually  cut.  The  means  required  in  such  cases  vary  with  the 
hardness  of  the  mineral  under  examination.  For  the  hardest  minerals  diamond  powder  is 
made  use  of  in  grinding;  it  is  employed  after  the  manner  of  the  lapidary.  (It  may  be  men- 
tioned here  that  the  investigator  will  generally  find  it  for  his  interests,  both  as  regards  time, 
money,  and  accuracy  of  results,  to  employ  a  lapidary  to  do  this  work  for  him. )  •  The  diamond 
powder  is  applied  to  a  thin  wheel  of  soft  iron  or  copper,  rotating  on  a  lathe. 

For  minerals  which  are  not  so  extremely  hard,  good  emery  may  be  used  instead  of  diamond 
powder.  It  is  merely  necessary  to  apply  the  emery  and  water  to  the  edge  of  the  wheel  as  it 
revolves,  the  mineral  being  held  firmly  against.  A  neater  and  more  advantageous  method, 
where  the  amount  of  material  is  small,  is  the  use  of  a  fine  saw,  or  better  wire,  mounted  in  a 
frame,  and  used  with  either  diamond  powder  or  emery  moistened  with  water  or  oil.  The 
crystal  may  be  mounted  in  wax  or  otherwise,  if  very  small ;  sometimes  a  holder  made  of  cork 
is  convenient. 

The  direction  in  which  the  slice  is  to  be  cut  is  of  the  highest  importance,  and  can  often  be 
indicated  at  first  by  a  scratch  across  a  plane  of  a  crystal.  In  many  cases  it  is  more  simple  to 
grind  on  a  surface  in  the  proper  direction,  and  this  can  be  easily  accomplished  by  holding  the 
crystal  against  a  fine-grained  emery  wheel  rotating  on  a  lathe.  It  can  be  held  either  in  the 
fingers,  or  cemented  to  a  small  piece  of  glass,  for  instance  with  Canada  balsam. 

Another  way.  more  simple  as  demanding  no  instruments,  is  to  make  use  of  a  flat  piece  of 
plate  glass,  not  too  small,  on  which  the  crystal  is  ground  with  moistened  emery,  being  care- 
fully moved  about  with  the  hand.  In  some  cases  a  file,  or  even  a  knife,  may  be  used,  where 
the  mineral  in  hand  is  soft. 

Whatever  method  of  grinding  is  adopted,  it  is  necessary  to  exercise  great  care  to  bring  the 
artificial  surface  into  exactly  the  proper  direction.  This  can  be  determined  only  as  its  inclina- 
tions to  existing  crystalline  planes,  or  cleavage  surfaces,  are  measured,  and  practically  it  is 
necessary  often  to  stop  the  work  and  test  what  has  been  done.  The  parallel  intersections 


156  PHYSICAL    CHARACTEES    OF   MINERALS. 

will  often  show  the  degree  of  correctness  in  the  work.  For  purposes  of  measurement  it  is 
necessary  to  polish  the  artificial  plane,  or  instead,  a  small  piece  of  thin  glass  may  be  cemented 
on  where  the  crystal  is  too  small  for  the  use  of  the  hand-goniometer.  It  is  of  course  necessary 
to  know,  before  starting,  the  angle  which  the  new  plane  will  make  with  the  natural  planes 
which  are  already  present.  When  one  plane  in  the  required  direction  has  been  obtained,  it 
is  a  comparatively  simple  process  to  obtain  a  second  parallel  to  it,  though  care  must  be  exer- 
cised to  attain  accuracy. 

The  required  section  having  been  cut,  it  remains  only  to  polish  the  surfaces.  The  means 
required  differ  so  widely,  according  to  the  hardness  of  the  mineral,  that  no  fixed  rule  can  be 
given.  The  most  commonly  used  polishing  powder  is  the  English  red,  or  colcothar,  which 
may  be  used  on  the  plate  of  glass,  or  leather  surface,  or  on  a  revolving  wheel  covered  with  a 
soft  cloth.  In  other  cases  oxide  of  tin  or  fine  chalk  is  used  ;  and  again  the  simple  plate  of 
ground  plass  will  answer  the  purpose  without  the  use  of  any  other  means.  As  a  rule,  the 
hardest  minerals  take  the  polish  most  readily.  Sometimes  the  only  method  practicable  is  to 
use  small  fragments  of  thin  glass,  adhering  with  balsam,  by  which  transparency  is  obtained 
without  polish,  though  errors  are  easily  introduced  by  this  means  when  sufficient  care  is  not 
exercised.  . 

The  preparation  of  prisms  for  the  measurement  of  the  indices  of  refraction  is  practically 
much  more  difficult  than  that  of  a  simple  section,  but  in  general  the  methods  are  the  same. 

It  is  often  advisable  to  examine  a  mineral  microscopically  when  a  slice  in  a  particular  direc- 
tion is  not  needed.  In  such  cases  use  can  be  made  of  the  methods  employed  in  making  rock 
slices.  A  revolving  wheel  of  soft  iron,  vertical  or  horizontal,  is  employed,  on  the  lateral  sur- 
face of  which  the  substance  is  ground  with  the  use  of  emery  moistened  with  water.  A  thin 
slice,  or  thin  fragment  broken  off,  is  taken  to  commence  with.  First  one  surface  is  ground 
smooth  and  polished.  The  piece  is  then  cemented  to  a  little  plate  of  thick  glass  with  balsam, 
and  the  other  side  ground  down  parallel  to  the  first,  the  grinding  being  continued  until  the 
required  degree  of  transparency  is  obtained.  Obviously  when  the  section  becomes  thin  and 
fragile,  the  coarse  emery  must  be  replaced  with  fine,  and  a  considerable  degree  of  care  exer- 
cised. The  section  obtained  is  generally  removed  to  another  slip  of  glass  and  mounted  with 
balsam  under  a  thin  glass  cover. 

The  microscopic  investigation  of  minerals,  by  means  of  thin  slices,  is  of  the  highest  import- 
ance, aside  from  optical  investigations.  Every  chemical  analysis  should  be  preceded  by  such, 
an  examination  to  test  the  purity  of  the  material  in  hand.  Where  a  transparent  section  can- 
not be  obtained,  a  single  polished  surface,  examined  by  reflected  light,  will  often  suffice  to 
decide  the  same  point. 

The  valuable  investigations  of  Vogelsang,  Fischer,  Rosenbusch,  and  others,  referred  to  on 
pp.  108  to  111,  show  how  many  minerals,  which  at  first  glance  seem  perfectly  pure,  are  found 
to  enclose  impurities  considerable  in  variety  and  amount. 

LITERATURE. — OPTICAL  CHARACTERS  OP  CRYSTALS. 

Brewster.     Treatise  on  Optics,  and  many  minor  papers  in  Ed.  Phil.  Mag.,  etc. 

Beer.      Einleitung  in  die  hohere  Optik  ;  Braunschweig,  1858. 

Dote.     Darstellung  der  Farbenlehre  und  optische  Studien  ;  Berlin,  1853. 

Grailich.     Krystallographisch-opt-'sche  Untersuchungen  ;  Wien,  1858. 

Grailich  u.  von  Lang.  Untersuchungen  iiber  das  physikalische  Verhalten  krystallisirter 
Korper;  Ber.  Ak.  Wien,  xxvii.  3;  xxxii.,  xxxiii.,  and  other  papers. 

DesGloizeaux.  Memoire  sur  les  proprietes  birefringentes  en  Mineralogie,  Ann.  d.  Mines; 
V.,  xi.,  1857;  xiv.,  1858. 

Memoire  sur  1'emploi  du  microscope  polarisant,  etc. ;  Paris,  1864. 

Nouvelles  Recherches  sur  les  proprietes  optiques  des  Cristaux,  etc.,  et^sur  les 

variations  que  ces  proprietes  eprouvent  sous  Finfluence  de  la  chaleur  ;  C.  R.,  Ixii.,  987,  1866. 

tichmuf.     Lehrbuch  der  physikalischeu  Mineralogie  ;  vol.  il,  Wien,  1868. 
Muller-Pouillet.     Lehrbuch  der  Physik  ;  vol.  i.,  Braunschweig,  1875. 
Wullner.     Lehrbuch  der  Experimental-Physik ;  vol.  ii.     Die  Lehre  vom  Licht ;  Leipzig, 
1871.  •%*  ! 

Roseribusoh.  Microscopische  Physiographic  der  petrographisch  wichtigen  Mineralien,  pp. 
55-107 ;  Stuttgart,  1873. 

Oroth.     Physikalische  Krystallographie  ;  Leipzig,  1876. 

Von  Kobell.     Ueber  ein  neues  Polariskop— Stauroskop  ;  Pogg.,  xcv.»  320,  1855. 

Brezina.     Eine  neue  Modification  des  Stauroskops,  etc.  ;  Pogg.,  cxxviii.,  448,  1866  ;  cxxx., 

Oroth.  '  Ueber  Apparate  und  Beobachtungsmethoden  fur  krystallographisch-optische 
Untersuchungen;  Pogg.,  cxliv,,  34,  1871. 


DIAPHANEITY — COLOR — LUSTKE.  157 


DIAPHANEITY;    COLOR;    LUSTRE. 

There  are  certain  characteristics  belonging  to  all  minerals  alike,  crystal- 
lized and  non-crystallized,  in  their  relation  to  light.     These  are  : 

1.  DIAPHANEITY;  depending  on  the  power  of  transmitting  light. 

2.  COLOR  ;  depending  on  the  kind  of  light  reflected  or  transmitted. 

3.  LUSTKE;  depending  on  the  power  and  manner  of  reflecting  light. 


1.  DIAPHANEITY. 

The  amount  of  light  transmitted  by  a  solid  varies  in  intensity,  or,  in  other 
words,  of  the  light  received  more  or  less  may  be  absorbed.  The  amount 
of  absorption  is  a  minimum  in  a  perfectly  transparent  solid,  as  ice,  while  it 
is  greatest  in  one  which  is  opaque,  as  iron.  The  following  terms  are  adopted 
to  express  the  different  degrees  in  the  power  of  transmitting  light : 

Transparent :  when  the  outline  of  an  object  seen  through  the  mineral  is 
perfectly  distinct. 

Subtransparent)  or  semi-transparent :  when  objects  are  seen,  but  the 
outlines  are  not  distinct. 

Translucent :  when  light  is  transmitted,  but  objects  are  not  seen. 

Siibtramlucent :  when  merely  the  edges  transmit  light  or  are  trans- 
lucent. 

When  no  light  is  transmitted,  the  mineral  is  said  to  ba  opaque.  This  is 
propei-ly  only  a  relative  term,  since  no  substance  fails  to  transmit  some 
light,  if  made  sufficiently  thin.  Magnetite  is  translucent  in  the  Pennsbury 
mica.  The  recent  researches  of  Prof.  A.  W.  Wright  have  shown  that  by 
means  of  the  electrical  current  the  metals  may  be  volatilized  and  deposited 
again  on  the  sides  of  the  surrounding  glass  tube.  The  layers  thus  formed 
are  perfectly  continuous,  but  so  thin  as  to  be  transparent.  *  By  transmitted 
light  the  layer  of  gold  thus  obtained  appears  green,  and  that  of  silver  a 
beautiful  bine. 

The  property  of  diaphaneity  occurs  in  the  mineral  kingdom,  in  every 
degree  from  nearly  perfect  opacity  to  a  perfect  transparency,  and  many 
minerals  present,  in  their  numerous  varieties,  nearly  all  the  different  shades. 

The  absorption  of  light  in  its  relation  to  the  axes  -of  elasticity  is  spoken 
of  on  p.  161. 

2.  COLOR. 

Cause  of  color. — The  color  of  a  substance  depends  upon  its  power  of 
absorbing  certain  portions  of  the  light,  that  is,  certain  rays  of  the  spectrum  ; 
a  yellow  mineral,  for  instance,  absorbs  all  the  rays  of  the  spectrum  with  the 
exception  of  the  yellow.  In  general  the  color  which  the  eye  perceives  is 
the  result  of  the  mixture  of  those  rays  which  are  not  absorbed.  All  min- 
erals may  be  divided  into  two  classes:  (1)  those  whose  color  is  essential  and 
belongs  to  the  tinest  particles  mechanically  made ;  (2)  those  whose  color  is 
non-essential  and  in  the  fine  powder  is  different  from  what  it  is  in  the  mass. 


158  PHYSICAL    CHARACTERS    OF   MINERALS. 

Streak. — It  is  obvious  from  these  distinctions  that  the  color  of  the 
powder,  or  the  streak,  as  it  is  called,  is  often  a  very  important  quality 
in 'distinguishing  minerals.  The  streak  is  obtained  by  scratching  the  sur- 
face of  the  mineral  with  a  knife  or  file,  or  still  better,  if  not  tpo  hard,  by 
rubbing  it  on  an  unpolished  porcelain  surface. 

To  the  first  class,  mentioned  above,  belong  the  metals,  and  many 
metallic  minerals;  for  instance,  the  streak  of  the  black  manganese  oxides  is 
black  ;  that  of  hematite,  which  is  red  by  transmitted  light,  is  red,  and  so 
on.  To  the  second  class  belong  the  silicates,  and  in  fact  the  large  part 
of  all  minerals.  With  them  the  color  is  often  quite  unessential,  being  gen- 
erally due  to  small  admixtures  of  some  metallic  oxide,  to  some  carbon  com- 
pound, or  some  foreign  substance  in  a  finely  divided  state.  Most  of  these 
have  a  white  or  light-colored  streak.  For  example,  the  streak  of  black, 
green,  red,  and  blue  tourmaline  varies  little  from  white. 


VARIETIES  OP  COLOR. 

The  following  eight  colors  have  been  selected  as  fundamental,  to  facilitate 
the  employment  of  this  character  in  the  description  of  minerals :  white, 
gray,  black,  blue,  green,  yellow,  red,  and  brown. 


•Metallic 

1.  Copper-red:  native  copper. — 2.  Bronze-yellow :  pyrrhotite. — 3.  Brass- 
yellow  :  chalcopyrite. — 4.  Gold-yellow. — 5.  Silver-white  :  native  silver,  less 
distinct  in  arsenopyrite. — 6.  Tin-white:  mercury,  cobaltite. — 1.  Lead-gray: 
galenite,  molybdenite. — 8.  Steel-gray :  nearly  the  color  of  fine-grained 
steel  on  a  recent  fracture ;  native  platinum,  and  palladium. 


s&.  Non-metallic  Colors. 

A.  WHITE.  1.  Snow-white :  Carrara  marble. — 2.  Reddish-white :   sonie 
varieties  of  calcite  and  quartz. — 3.    Yellowish-white  :  some  varieties  of  cal- 
cite and  quartz. — 4.   Grayish-white :  some  varieties  of  calcite  and  quartz. 
— 5.   Greenish-white  :  talc. — 6.  Milk-white :  white,  slightly  bluish  ;  some 
chalcedony. 

B.  GRAY.  1.  Bluish-gray :    gray,  inclining  to  a  dirty  blue  color. — 2. 
Pearl-gray:  gray,  mixed  with  red  and  blue  ;  cerargyrite. — 3.  Smoke-gray: 
gray,  with  some  brown  ;  flint. — 4.   Greenish-gray :  gray,  with  some  green  ; 
cat's  eye,  some  varieties  of  talc. — 5.    Yellowish-gray :    some  varieties  of 
compact  limestone. — 6.  Ash-gray  :  the  purest  gray  color  ;  zoisite. 

C.  BLACK.    1.    Grayish-black:    black,   mixed   with  gray    (without   any 
green,  brown,  or  blue  tints) ;  basalt,  Lydian  stone. — 2.    Velvet-black  :  pure 
black ;  obsidian,  black  tourmaline. — 3.  Greenish-black:  angite. — 4.  Brown- 
ish-black :  bi'own  coal,  lignite. — 5.  Bluish-black  :  black  cobalt. 

D.  BLUE.  1.  Blackish-blue :  dark  varieties  of  azurite. — 2.  Azure-blue  : 
a  clear  shade  of  bright  blue ;  pale  varieties  of  azurite,  bright  varieties  of 


DIAPHANEITY COLOR — LUSTRE.  159 

lazulite. — 3.  Violet-Hue:  blue,  mixed  with  red;  amethyst,  fluorite. — 4. 
Lavender-blue :  blue  with  some  red  and  much  gray. — 5.  Prussian-blue^ 
or  Berlin  blue  :  pure  blue  ;  sapphire,  cyanite. — 6.  Smalt-blue:  some  varie- 
ties of  gypsum. — 7.  Indigo-blue  :  blue  with  black  and  green  ;  blue  tourma- 
line.— 8.  Sky-blue:  pale  blue  with  a  little  green;  it  is  called  mountain 
blue  by  painters. 

E.  G-REEN.  1.    Verdigris-green :  green  inclining  to  blue ;  some  feldspar 
(amazon-stone). —  Celandine-green:  green  with  blue  and  gray  ;  some  varie- 
ties of  talc  and  beryl.     It  is  the  color  of  the  leaves  of  the  celandine  (Cheli- 
doninm  rnajus). — 3.  Mountain-green  :  green  with  much  blue ;  beryl. — 4. 
Leek-green :  green  with  some  brown  ;  the  color  of  leaves  of  garlic  ;  dis- 
tinctly seen  in  prase,  a  variety  of  quartz. — 5.  Emerald-green  :  pure  deep 
green  ;  emerald. — 6.  Apple-green  :  light  green  with  some  yellow  ;  chryso- 
prase. — 7.   Grass-green :  bright  green  with  more  yellow  ;  green  diallage. — 
8.  Pistachio -green  :  yellowish  green  with  some  brown  ;  epidote. — 9.  Aspa- 
ragus-green :  pale  green  with  much 'yellow;  asparagus  stone  (apatite). — 
10.  Blackish-green;  serpentine. — 11.   Olive-green:  dark  green  with  much 
brown  and  yellow ;    chrysolite. — 12.   Oil-green :    the  color  of   olive  oil ; 
beryl,  pitchstone. — 13.  Siskin-green :  light  green,  much  inclining  to  yellow; 
uranite. 

F.  YELLOW.  1 .  Sulphur-yellow  :    sulphur. — 2.  Straw-yellow  :    pale  yel- 
low ;  topaz. — 3.    Wax-yellow :  grayish  yellow  with  some  brown  ;  blende, 
opal. — 4.  Honey-yellow  :  yellow  with  some  red  and  brown ;    calcite. — 5. 
Lemon-yellow:  sulphur,  orpiment. — 6.   Ochre-yellow:  yellow  with  brown  ; 
yellow  ochre. — 7.    Wine-yellow  :    topaz   and  fluorite. — 8.    Cream-yellow : 
some  varieties  of  lithomarge. — 9.   Orange-yellow :  orpiment. 

G.  RED.  1.  Aurora-red:    red    with   much   yellow;    some   realgar. — 2. 
Hyacinth-red:    red  with  yellow  and  some  brown  ;  hyacinth  garnet. — 3. 
Brick-red:    polyhalite,  some  jasper. — 4.  Scarlet-red:    bright  red  with    a 
tinge  of  yellow;  cinnabar. — 5.  Blood-red:  dark  red   with  some  yellow; 
pyrope. — 6.  Flesh-red:  feldspar.— 7.   Carmine-red:  pure  red;    ruby  sap- 
phire.— 8.  Rose-red  :    rose  quartz. — 9.   Crimson-red :    ruby. — 10.    Peach- 
blossom-red:  red  with  white  and  gray;    lepidolite. — 11.   Colmnbine-red : 
deep  red  with  some  blue ;  garnet. — 12.   Cherry-red :  dark  red  with  some 
blue  and  brown:  spinel,  some  jasper. — 13.  Brownish-red:  jasper,  limonite. 

II.  BROWN.  1.  Reddish-brown :  garnet,  zircon. — 2.  Clove-brown:  brown 
with  red  and  some  blue  ;  axinite. — 3.  Hair-brown  :  wood  opal. — 4.  Broc- 
coli-brown :  brown,  with  blue,  red,  and  gray  ;  zircon. — 5.  Chestnut-brown  : 
pure  brown. — 6.  Yellowish-brown :  jasper. — 7.  Pinchbeck-brown  :  yellow- 
ish-brown, with  a  metallic  or  metallic-pearly  lustre ;  several  varieties  of 
talc,  bronzite. — 8.  Wood-brown:  color  of  old  wood  nearly  rotten  ;  some 
specimens  of  asbestus. — 9.  Liver-brown :  brown,  with  some  gray  and  green ; 
jasper. — 10.  Blackish-brown  ;  bituminous  coal,  brown  coal. 

c.  Peculiarities  in  the  Arrangement  of  Colors. 

Play  of  Colors. — An  appearance  of  several  prismatic  colors  in  rapid 
succession  on  turning  the  mineral.  This  property  belongs  in  perfection  to 
the  diamond ;  it  is  also  observed  in  precious  opal,  and  is  most  brilliant  by 
candle-light. 


160  PHYSICAL    CHARACTERS    OF    MINERALS. 

Change  of  Colors. — Each  particular  color  appears  to  pervade  a  larger 
space  than  in  the  play  of  colors,  and  the  succession  produced  by  turning  the 
mineral  is  less  rapid;  Ex.  labradorite. 

Opalescence. — A  milky  or  pearly  reflection  from  the  interior  of  a  speci- 
men. Observed  in  some  opal,  and  in  cat's  eye.  ^__^^ 

Iridescence. — Presenting  prismatic  colors  in  the  interior  of  a"  crystal. 
The  phenomena  of  the  play  of  colors,  iridescence,  etc.,  are  sometimes/to  be 
explained  by  the  presence  of  minute  foreign  crystals,  in  parallel  positions ; 
more  generally,  however,  they  are  caused  by  the  presence  of  fine  cleavage 
lamellae,  in  the  light  reflected  from  which  interference  takes  place,  analogous 
to  the  well-known  Newton's  rings. 

Tarnish. — A  metallic  surface  is  tarnished,  when  its  color  differs  from 
that  obtained  by  fracture  ;  Ex.  bornite.  A  surface  possesses  the  steel  tar- 
nish, when  it  presents  the  superficial  blue  color  of  tempered  steel ;  Ex. 
columbite.  The  tarnish  is  irised,  when  it  exhibits  fixed  prismatic  colors  ; 
Ex.  hematite  of  Elba.  These  tarnish  and  iris  colors  of  minerals  are  owing 
to  a  thin  surface  film,  proceeding  from  different  sources,  either  from  a 
change  in  the  surface  of  the  mineral,  or  foreign  incrustation  ;  hyd rated  iron 
oxide,  usually  formed  from  pyrite,  is  one  of  the  most  common  sources  of  it, 
and  produces  the  colors  on  anthracite  and  hematite. 

Aster  ism. — This  name  is  given  to  the  peculiar  star-like  rays  of  light 
observed  in  certain  directions  in  some  minerals  by  reflected  or  transmitted 
light.  This  is  seen  in  the  form  of  a  six-rayed  star  in  sapphire,  and  is  also 
well  shown  in  mica  from  South  Burgess,  Canada.  In  the  former  case  it 
has  been  attributed  by  Volger  to  a  -repeated  lamellar  twinning  ;  in  the 
other  case,  by  Rose,  to  the  presence  of  minute  inclosed  crystals,  which  are 
a  uniaxial  mica,  according  to  DesCloizeaux.  Crystalline  planes,  which 
have  been  artificially  etched,  also  sometimes  exhibit  asterism.  In  general 
the  phenomenon  is  explained  by  Schrauf  as  caused  by  the  interference  of 
the  light,  due  to  fine  striations  or  some  other  cause.  ^/ 

(-Upon  the  above  subjects,  see  Literature,  p.  1-63.) 

PHOSPHORESCENCE. 

Phosphorescence,*  or  the  emission  of  light  by  minerals,  may  be  produced 
in  different  ways :  \>y  friction,  by  heat,  or  by  exposure  to  light. 

By  friction. — Light  is  readily  evolved  from  quartz  or  white  sugar  by 
the  friction  of  one  piece  against  another,  and  merely  the  rapid  motion  of  a 
feather  will  elicit  it  from  some  specimens  of  sphalerite.  Friction,  however, 
evolves  light  from  a  few  only  of  the  mineral  species. 

l$y  heat. — Fluorite  is  highly  phosphorescent  at  the  temperature  of  300°  F. 
Different  varieties  give  off  light  of  different  colors  ;  the  Morophane  variety, 
an  emerald-green  light ;  others' purple,  blue,  and  reddish  tints.  This  phos- 
phorescence may  be  observed  in  a  dark  place,  by  subjecting  the  pulverized 
mineral  to  a  heat  below  redness.  Some  varieties  of  white  limestone  or 
marble  emit  a  yellow  light. 

*  This  subject  has  been  investigated  by  Becquerd,  Ann.  Ch.  Phys.,  III.,  lv.,  5-119,  1859  ; 
Faster,  Mitth.  nat.  Ges.  Bern,  1867,  62;  and  Hahn,  Zeitsch.  Ges.  nat.  Wiss.  Berlin,  II., 
ix.,  1,131,  1874. 


DIAPHANEITY COLOR — LUSTRE.  161 

By  the  application  of  heat,  minerals  lose  their  phosphorescent  properties.  *  But  on  passing 
electricity  through  the  calcined  mineral,  a  more  or  less  vivid  light  is  produced  at  the  time  of 
the  discharge,  and  subsequently  the  specimen  when  heated  will  often  emit  light  as  before. 
The  light  is  usually  of  the  same  color  as  previous  to  calcination,  but  occasionally  is  quite 
different.  It  is  in  general  less  intense  than  that  of  the  unaltered  mineral,  but  is  much 
increased  by  a  repetition  of  the  electric  discharges,  and  in  some  varieties  of  fluorite  it  may 
be  nearly  or  quite  restored  to  its  former  brilliancy.  It  has  also  been  found  that  some  varie- 
ties of  fluorite  and  some  specimens  of  diamond,  calcite,  and  apatite,  which  are  not  naturally 
phosphorescent,  may  be  rendered  so  by  means  of  electricity.  Electricity  will  also  increase 
the  natural  intensity  of  the  phosphorescent  light. 

Light  of  the  sun. — The  only  substance  in  which  an  exposure  to  the  light 
of  the  sun  produces  very  apparent  phosphorescence  is  the  diamond,  and 
some  specimens  seem  to  be  destitute  of  this  power.  This  property  is  most 
striking  after  exposure  to  the  blue  rays  of  the  spectrum,  while  in  the  red 
rays  it  is  rapidly  lost. 


PLEOCHKOISM. 

Dichroism,  Trichroism. — In  addition  to  the  general  phenomena  of  color, 
which  belong  to  all  minerals  alike,  some  of  those  which  are  crystallized 
show  different  colors  under  certain  circumstances.  This  is  due  to  the  fact 
that  in  them  the  absorption  of  parts  of  the  spectrum  takes  place  unequally 
in  different  directions,  and  hence  their  color  by  transmitted  light  depends 
upon  the  direction  in  which  they  are  viewed.  This  phenomenon  is  called 
in  general  pleochroism. 

In  uiiiaxial  crystals  it  has  been  seen  that,  in  consequence  of  their  crystal- 
lographic  symmetry,  there  are  two  distinct  values  for  the  velocity  of  light 
transmitted  by  them,  according  as  the  vibrations  take  place  j  parallel  or  at 
rig/it  angles  to  the  vertical  axis.  Similarly  the  crystal  may  exert  different 
degrees  of  absorption  upon  the  rays  vibrating  in  these  two  directions.  For 
example,  a  transparent  crystal  of  zircon  looked  through  in  the  direction  of 
the  vertical  axis  appears  of  a  pinkish-brown  color,  while  in  a  lateral  direc- 
tion the  color  is  asparagus-green.  This  is  because  the  rays  (extraordinary) 
vibrating  parallel  to  the  axis  are  absorbed  with  the  exception  of  those 
which  together  give  the  green  color,  and  those  vibrating  laterally  (ordinary) 
are  absorbed  except  those  which  together  appear  pinkfsh-brown. 

Again,  all  crystals  of  tourmaline  in  the  direction  of  the  vertical  axis  are 
opaque,  since  the  ordinary  ray,  vibrating  normal  to  the  axis  c,  is  absorbed, 
while  light-colored  varieties,  looked  through  laterally,  are  transparent,  for 
the  extraordinary  ray,  vibrating  parallel  to  c,  is  not  absorbed  ;  the  color 
differs  in  different  varieties.  Thus,  all  uniaxial  crystals  may  be  dichroic, 
or  have  two  distinct  axial  colors. 

Similarly  all  biaxial  crystals  may  be  trichroic.  For  the  rays  vibrating  in 
the  directions  of  the  three  axes  of  elasticity  may  be  differently  absorbed. 
For  diaspore  the  three  axial  colors  are  azure-blue,  wine-yellow,  and  violet- 
blue.  It  will  be  understood  that,  while  these  three  different  colors  are  pos- 
sible, they  may  not  exist ;  or  only  two  may  be  prominent,  so  that  a  biaxial 
mineral  may  be  called  dichroic. 

In  order  to  investigate  the  absorption-properties  of  any  uniaxial  or  biaxial 
crystal,  it  is  evident  that  sections  must  be  obtained  which  are  parallel  to  the 


162 


PHYSICAL   CHARACTERS    OF   MINERALS. 


410 


several  axes  of  elasticity.  Suppose  that  f.  410  represents  a  rectangular  solid 
with  its  sides  parallel  to  the  three  axes  of  elasticity  of 
a  biaxial  crystal.  In  an  orthorhombic  crystal  the  faces 
are  those  of  the  three  diametral  planes  or  pinacoids  ; 
in  a  monoclinic  crystal  one  side  coincides  with  the  clino- 
pinacoid,  the  others  are  to  be  determined  for  each 
species.  The  light  transmitted  by  this  solid  is  examined 
by  means  of  a  single  Nicol  prism.  Suppose,  first,  that 
the  light  transmitted  by  the  parallelepiped  (f.  410)  in 
the  direction  of  the  vertical  axis  is  to  be  examined. 
When  the  shorter  diagonal  of  the  Nicol  coincides  with 
the  direction  of  the  axis  b,  the  color  observed  belongs 
to  that  ray  vibrating  parallel  to  this  direction  ;  when  it  coincides  with  the 
axis  a,  the  color  for  the  ray  with  vibrations  parallel  to  a  is  observed.  In 
the  same  way  the  Nicol  separates  the  different  colored  rays  vibrating 
parallel  to  c  and  a  respectively,  when  the  light  passes  through  in  the  direc- 
tion of  b. 

So  also  finally  when  the  section  is  looked  through  in  the  direction  of  the 
axis  a,  the  colors  for  the  rays  vibrating  parallel  to  b  and  c,  respectively,  are 
obtained.  It  is  evident  that  the  examination  in  two  of  the  directions  named 
will  give  the  three  possible  colors. 

For  epidote,  according  to  Klein,  the  colors  for  the  three  axial  directions 
are : 


.,     Vibrations  parallel  to  b,  brown  (absorbed). 
"  "  a,  yellow. 


o     Vibrations  parallel  to  t ,  green. 

u  "  a,  yellow. 


o     Vibrations  parallel  to  f,  green, 

"  "  b,  brown  (absorbed). 

The  colors  observed  by  the  eye  alone  are  the  resultants  of  the  double  set 
of  vibrations,  in  which  the  stronger  color  predominates  ;  thus,  in  the  above 
example,  the  plane,  normal  to  c  is  brown,  to  b,  yellowish-green,  to  a,  green. 
In  any  other  direction  in  the  crystal,  the  apparent  color  is  the  result  of  a 
mixture  of  those  corresponding  to  the  three  directions  of  vibrations  in  differ- 
ent proportions.  Dichroite  is  a  striking  example  of  the  phenomenon  of 
pleochroism. 

An  instrument  called  a  dichroscope  has  been  contrived  by  Haidinger  for 
examining  this  property  of  crystals.  An  oblong  rhornbohedron  of  Ice- 
land spar  has  a  glass  prism  of  18°  cemented  to  each  extremity.  It  is  placed 


411 


412 


in  a  metallic  cylindrical  case,  as  in  the  figure,  having  a  convex  lens  at  one 
•end,  and  a  square  hole  at  the  other.  On  looking  through  it,  the  square  hole 
appears  double ;  one  image  belongs  to  the  ordinary  and  the  other  to  the 
extraordinary  ray.  When  apleochroic  crystal  is  examined  with  it,  by  trans- 
mitted light,  on  revolving  it,  the  two  squares,  at  intervals  of  90°  in  the  revo- 


DIAPHANEITY COLOR LUSTRE.  163 

lution,  have  different  colors,  corresponding  to  the  direction  of  the  vibrations 
of  the  ordinary  and  extraordinary  ray  in  calcite.  Since  the  two  images  are 
situated  side  by  side,  a  very  slight  difference  of  color  is  perceptible. 


LITERATURE. — PLEOCHROISM,  ASTERISM,  ETC. 

Haidinger.     Ueber  den  Pleochroismus  der  Krystalle  ;  Pogg.  Ixv.,  1,  1845. 

Ueber  das  Schillern  der  Krystallflachen ;  Pogg.  hex,  574,  1847;  Ixxi.,  321; 

Ixxvi.,  99,  1849. 

Reusch.  Ueber  das  Schillern  gewisser  Krystalle;  Pogg.  cxvi.,  392,  1862;  cxviii.,  256, 
1863;  cxx.,  95,  1863. 

v.  Kobell.     Ueber  Asterismus;  Ber.  Ak.    Miinchen,  1863,  65. 

HausJwfer.     Der  Asterismus  des  Calcites  ;  Ber.  Ak.     Miinchen,  1869. 

Vogelsang.     Sur  le  Labradorite  colore  ;  Arch.  Neerland. ,  iii.,  32,  1868. 

Schrauf.     Labradorit;   Ber.  Ak.,  Wien,  lx.,  1869. 

Kosmann.  Ueber  das  Schillern  und  den  Dichroismus  des  Hypersthens ;  Jahrb.  Min.,  1869, 
368,  532;  1871,  501. 

Rose.     Ueber  den  Asterismus  der  Krystallen  ;  Ber.  Ak.    Berlin,  1862,  614  ;  1869,  344. 


3.  LUSTRE. 

The  lustre  of  minerals  varies  with  the  nature  of  their  surfaces.  A  varia- 
tion in  the  quantity  of  light  reflected,  produces  different  degrees  of  intensity 
of  lustre  ;  a  variation  in  the  nature  of  the  reflecting  surface  produces 
different  kinds  of  lustre. 

A,  The  kinds  of  lustre  recognized  are  as  follows  : 

1.  Metallic  :  the  lustre  of  metals.     Imperfect  metallic  lustre  is  expressed 
by  the  term  sub-metallic. 

2.  Adamantine:  the  lustre  of  the  diamond.     When  also  sub-metallic,  it 
is  termed  metallic-adamantine.     Ex.  cerussite,  pyrargyrite. 

3.  Vitreous :  the  lustre  of  broken  glass.     An  imperfectly  vitreous  lustre 
is  termed  sub-vitreous.     The  vitreous  and  sub-vitreous  lustres  are  the  most 
common  in  the  mineral  kingdom.     Quartz  possesses  the  former  in  an  emi- 
nent degree ;  calcite,  often  the  latter. 

4.  Resinous :  lustre  of  the  yellow  resins.     Ex.  opal,  and  some  yellow 
varieties  of  sphalerite. 

5.  Pearly :  like  pearl.     Ex.  talc,  brucite,  stilbite,  etc.     When  united  with 
sub-metallic,  as  in  hypersthenite,  the  term  metallic-pearly  is  used. 

6.  Silky :  like  silk ;  it  is  the  result  of  a  fibrous  structure.    'Ex.  fibrous 
calcite,  fibrous  gypsum. 

B.  The  degrees  of  intensity  are  denominated  as  follows: 

1.  Splendent :  reflecting  with  brilliancy  and  giving  well-defined  images. 
Ex.  hematite,  cassiterite. 

2.  Shining :  producing  an  image  by  reflection,  but  not  one  well  defined. 
Ex.  celestite. 

3.  Glistening :  affording  a  general  reflection  from  the  surface,  but  no 
image.     Ex.  talc,  chalcopyrite. 

4.  Glimmering:    affording  imperfect  reflection,  and  apparently  from 
points  over  the  surface.     Ex.  flint,  chalcedony. 

A  mineral  is  said  to  be  dull  when  there  is  a  total  absence  of  lustre.  Ex. 
chalk,  the  ochres,  kaolin. 


164  PHYSICAL    CHARACTERS   OF    MINERALS. 

The  true  difference  between  metallic  and  vitreous  lustre  is  due  to  the 
effect  which  the  different  surfaces  have  upon  the  reflected  light ;  in  general, 
the  lustre  is  produced  by  the  union  of  two  simultaneous  impressions  made 
upon  the  eye.  If  the  light  reflected  from  a  metallic  surface  be  examined 
by  a  N~icol  prism  (or  the  dichroscope  of  Haidinger),  it  will  be  found  that 
both  rays,  that  vibrating  in  the  plane  of  incidence  and  that  whose  vibra- 
tions are  normal  to  it,  are  alike,  each  having  the  color  of  the  material,  only 
differing  a  little  in  brilliancy  ;  on  the  contrary,  of  the  light  reflected  by  a 
vitreous  substance,  those  rays  whose  vibrations  are  at  right  angles  to  the 
plane  of  incidence  are  more  or  less  polarized,  and  are  colorless,  while  those 
whose  vibrations  are  in  this  plane,  having  penetrated  somewhat  into  the 
medium  and  suffered  some  absorption,  show  the  color  of  the  substance 
itself.  A  plate  of  red  glass  thus  examined  will  show  a  colorless  and  a  red 
image.  Adamantine  lustre  occupies  a  position  between  the  others. 

The  different  degrees  and  kinds  of  lustre  are  often  exhibited  differently  by  unlike  faces  of 
the  same  crystal,  but  always  similarly  by  like  faces.  The  lateral  faces  of  a  right  square 
prism  may  thus  differ  from  a  terminal,  and  in  the  right  rectangular  prism  the  lateral  faces 
also  may  differ  from  one  another.  For  example,  the  basal  plane  of  apophyllite  has  a  pearly 
lustre  wanting  in  the  prismatic  planes.  The  surface  of  a  cleavage  plane  in  foliated  minerals, 
very  commonly  differs  in  lustre  from  the  sides,  and  in  some  cases  the  latter  are  vitreous, 
while  the  former  is  pearly.  As  shown  by  Haidinger,  only  the  vitreous,  adamantine,  and 
metallic  lustres  belong  to  faces  perfectly  smooth  and  pure.  In  the  first,  the  index  of  refrac- 
tion of  the  mineral  is  1  '3 — 1  '8  ;  in  the  second,  1-9 — 2  '5  ;  in  the  third,  about  2 '5.  The  pearly 
lustre  is  a  result  of  reflection  from  numberless  lamella?  or  lines  within  a  translucent  mineral, 
as  long  since  observed  by  Breithaupt. 

IY.  HEAT. 

The  expansion  of  crystallized  minerals  by  heat  depends,  as  directly  as 
their  optical  properties,  on  the  symmetry  of  their  molecular  structure  as 
shown  in  their  crystalline  form.  The  same  three  classes  as  before  are  dis- 
tinguished : 

A.  Isometric  crystals,  where  the  expansion  is  in  all  directions  alike. 

B.  Isodmmetric  crystals,  of  the  tetragonal  and  hexagonal  systems.     Ex- 
pansion vertically  unlike  that  laterally,  but  in  all  lateral  directions  alike. 

C.  Anisometnc,  of  the  orthorhombic,  monoclinic,  and  triclinic  systems. 
Expansion  unlike  in  the  three  axial  directions.     The  expansion  by  heat  in 
the  case  of  crystals  may  serve  to  alter  the  angles  of  the  form,  but  it  has 
been  shown  that  the  zone  relations  and  the  crystalline  system  remain  con- 
stant. 

Mitscherlich  found  that  in  calcite  there  was  a  diminution  of  8'  37"  in  the  angle  of  the 
rhombohedron.  on  passing  from  32°  to  212°  F.,  the  form  thus  approaching  that  of  a  cube,  as 
the  temperature  increased.  Dolomite,  in  the  same  range  of  temperature,  diminishes  4'  40"; 
and  in  aragonite,  between  63°  and  212°  F.,  the  angle  of  the  prism  diminishes  2'  46',  and 
\-i  :  l-£  increases  5  30";  in  gypsum,  /:  i-\  is  increased  5  24",  /:  1,  4  12",  and  1-4  :  i-i  is 
diminished  7  24".  In  some  rhombohedrons,  as  of  calcite,  the  vertical  axis  is  lengthened 
(and  the  lateral  shortened),  while  in  others,  like  quartz,  the  reverse  is  true.  The  variation 
is  such  either  way  that  the  double  refraction  is  diminished  with  the  increase  of  heat ;  for 
calcite  possesses  negative  double  refraction,  and  quartz,  positive. 

The  conductive  power  of  a  crystal  depends,  as  does  expansion,  on  the 
symmetry  of  its  crystalline  form ;  this  is  also  true  of  its  power  of  trans- 


ELECTRICITY MAGNETISM.  165 

mitting  or  absorbing  heat.  It  follows,  moreover,  from  the  analogous  nature 
of  heat  and  light,  that  heat  rays  are  polarized  by  reflection,  and  by  transmission 
in  anisotrope  media,  in  the  same  way  as  the  rays  of  light.  These  subjects, 
considered  solely  in  their  relation  to  Mineralogy,  are  of  minor  importance ; 
they  belong  to  works  on  Physics,  and  reference  may  be  made  to  those 
whose  titles  are  given  in  the  Introduction,  as  also  to  the  works  of  Schrauf 
and  Groth. 

The  change  in  the  optical  properties  of  crystals  produced  by  heat  has 
already  been  noticed  (p.  153). 


Y.  ELECTRICITY— MAGNETISM. 

The  electric  and  magnetic  characters  of  crystals,  as  their  relations  to  heat, 
bear  but  slightly  upon  the  science  of  mineralogy,  although  of  high  interest 
to  the  student  of  physics. 

F fictional  electricity. — The  development  of  electricity  ~by  friction  is  a 
familiar  fact.  All  minerals  become  electric  by  friction,  although  the 
degree  to  which  this  is  manifested  depends  upon  their  conducting  or  non- 
conducting power.  There  is  no  line  of  distinction  among  minerals,  divid- 
ing them  \\\to positively  electric  and  negatively  electric;  for  both  kinds  of 
electricity  may  be  presented  by  different  varieties  of  the  same  species,  and 
by  the  same  variety  in  different  states.  The  gems  are  positively  electric 
only  when  polished  ;  the  diamond  alone  among  them  exhibits  positive  elec- 
tricity whether  polished  or  not.  The  time  of  retaining  electric  excitement 
is  widely  different  in  different  species,  and  topaz  is  remarkable  for  continu- 
ing excited  many  hours. 

Pressure  also  develops  electricity  in  many  minerals ;  calcite  and  topaz 
are  examples. 

Pyro-electricity. — A  decided  change  of  temperature,  through  heat  or 
cold,  develops  electricity  in  a  large  number  of  minerals,  which  are  hence 
called  pyro-electric.  This  property  is  most  decided,  and  was  first  observed 
in  a  series  of  minerals  which  are  hemimorphic  or  hemihedrai  in  their 
development.  The  electricity  in  these  minerals  is  of  opposite  character  in 
the  parts  dissimilarly  modified.  Thus  in  tourmaline  and  calamine,  the 
crystals  of  which  are  often  differently  modified  at  the  two  extremities,  posi- 
tive and  negative  electricity  are  developed  at  these  extremities  or  poles 
respectively.  When  the  extremity  becomes  positive  on  heating  it  has  been 
called  the  analogue  pole,  and  when  it  becomes  negative,  it  has  been  called 
the  antilogue.  The  names  were  given  by  Rose  and  Riess,  who  investigated 
these  phenomena.  For  a  change  of  temperature  in  the  opposite  direction, 
that  is,  cooling,  the  reverse  electrical  effect  is  observed. 

Boracite,  on  whose  crystals  the  +  and  —  tetrahedrons  often  occur,  shows 
by  heating  the  positive  electricity  for  the  faces  of  one  tetrahedron  and  the 
negative  for  those  of  the  other. 

Further  investigations  by  Hankel  and  others  (see  Literature)  have  ex- 
tended the  subject  and  shown  that  the  phenomena  of  pyro-electricity  belong 
to  the  crystals  of  a  large  number  of  species.  Moreover,  it  is  not,  as  once 
supposed,  essentially  connected  with  hemihedrai  development.  The  num- 
ber of  poles,  too,  may  be  more  than  two,  that  is,  the  points  at  which  posi- 


166  PHYSICAL   CHARACTERS    OF   MINERALS. 

live  and  negative  electricity  is  developed.  Thus  for  prehnite  there  is  a 
large  series  of  such  poles,  distributed  over  the  surface  of  a  crystal.  The 
investigations  of  Hankel  have  shown  in  general,  that  in  crystals  not  hemi- 
hedrally  developed,  the  same  electricity  is  developed  at  both  extremities  of 
the  same  axis,  and  the  distinction  between  positive  and  negative  electricity 
is  only  shown  by  reference  to  the  different  crystallographic  axes ;  on  sym- 
metrically formed  crystals  of  the  isodiametric  class  the  electricity  is  the 
same  in  all  lateral  directions,  that  is,  on  all  prismatic  planes,  while  different 
at  the  extremities  of  the  vertical  axis. 

Thermo-electricity. — When  two  different  metals  are  brought  into  con- 
tact, a  stream  of  electricity  passes  from  one  to  the  other.  If  one  is  heated 
the  effect  is  more  decided  and  is  sufficient  to  deflect  more  or  less  vigorously 
the  needle  of  a  galvanometer.  According  to  the  direction  of  the  current 
produced  by  the  different  metallic  substances,  they  are  arranged  in  a 
thermo-electrical  series;  the  extremes  are  occupied  by  antimony  (  +  )  and 
bismuth  ( — ),  the  electrical  stream  passing  from  bismuth  to  antimony. 

This  subject  is  so  far  important  for  mineralogy,  as  it  was  shown  by 
Bunsen  that  the  natural  metallic  sulphides  stand  further  off  in  the  series 
than  antimony  and  bismuth,  and  consequently  by  them  a  stronger  stream 
is  produced.  The  thermo-electrical  relations  of  a  large  number  of  minerals 
was  determined  by  Flight  (Ann.  Ch.  Pharm.,  cxxxvi.). 

It  was  early  observed  that  some  minerals  have  varieties  which  are  both 
+  and  — .  This  fact  was  made  use  of  by  Rose  to  show  a  relation  between 
the  plus  and  minus  hemihedral  varieties  of  pyrite  and  cobaltite.  The  later 
investigations  of  Schrauf  and  Dana  have  shown,  however,  that  the  same 
peculiarity  belongs  also  to  glaucodot,  tetradymite,  skutterudite,  danaite,  and 
other  minerals,  and  it  is  demonstrated  by  them  that  it  cannot  be  dependent 
upon  crystalline  form,  but,  on  the  contrary,  upon  chemical  composition. 

MAGNETISM. — The  magnetic  properties  of  crystals  are  theoretically  of 
interest,  since  they,  too,  like  the  optical  and  thermic,  are  directly  dependent 
upon  the  form  ;  hence,  with  relation  to  magnetism  they  group  themselves 
into  the  same  three  classes  before  referred  to. 

All  substances  are  divided  into  two  classes,  the  paramagnetic  and  dia- 
magnetic,  according  as  they  are  attracted  or  repelled  by  the  poles  of  a  mag- 
net. For  purposes  of  experiment  the  substance  in  question,  in  the  form  of 
a  rod,  is  suspended  between  the  poles  of  the  magnet,  being  movable  on  a 
horizontal  axis.  If  of  the  first  class,  it  will  take  a  position  parallel,  and  if 
of  the  second  class,  transverse,  to  the  magnetic  axis. 

By  the  use  of  a  sphere  it  is  possible  to  determine  the  relative  amount  of 
magnetic  induction  in  different  directions  of  the  same  substance.  Experi- 
ment has  showrn  that  in  isometric  crystals  the  magnetism  is  alike  in  all 
directions  ;  in  those  optically  uniaxial,  that  there  is  a  direction  of  maximum 
and,  normal  to  it,  one  of  minimum  magnetism  ;  in  biaxial  crystals,  that 
there  are  three  unequal  axes  of  magnetism,  the  position  of  which  may  be 
determined. 

A  few  minerals  have  the  power  of  exerting  a  sensible  influence  upon  the 
magnetic  needle,  and  are  hence  said  to  be  magnetic.  This  is  true  of  mag- 
netite and  pyrrhotite  (magnetic  pyrites)  in  particular,  also  of  franklinite, 
almaiidite,  and  other  minerals,  containing  considerable  iron  protoxide  (FeO). 
"When  such  minerals  in  one  part  attract  and  in  another  repel  the  poles  of 


TASTE   AND    ODOR.  167 

the  magnet,  they  are  said  to  possess  polarity.     This  is  true  of  the  variety  of 
magnetite  called  in  popular  language  loadstone. 

LITERATURE.—  ELECTRICITY. 

Hankel.  Ueber  die  Thermo-Electricitat  der  Krystalle;  Pogg.,  xlix.,  493;  1.,  237,  1840; 
Ixi.,  281. 

Rose  u.  Hies.     Ueber  die  Pyro-Electricitat  der  Mineralien  ;  Ber.  Ak.    Berlin,  1843. 

— Ueber  den  Zusammenhang  zwischen  der  Form  und  der  elektrischen  Polaritat  der 

Krystalle ;  Ber.  Ak.    Berlin,  1836. 

v.  Kobell.     Ueber  Mineral-Electricitat ;  Pogg.,  cxviii.,  594,  1863. 

Bunsen.     Thermo-Ketten  von  grosser  Wirksamkeit ;  Pogg.,  cxxiii.,  505,  1864. 

Friedel  Sur  les  proprietes  pyro-electrique  des  Cristaux  bons  conducteurs  de  Telectricite ; 
Ann.  Ch.  Phys.,  IV.,  xvii.,  79,  1869. 

Rose.  Ueber  den  Zusammenhang  zwischen  hemiedrischer  Krystallform  und  thermo-elek- 
trischem  Verhalten  beim  Eisenkies  und  Kobaltglanz  ;  Pogg.,  cxlii.,  1,  1871. 

Schrauf u.  E.  S.  Dana.  Ueber  die  thrrmo-elektrischen  Eigenschaften  von  Mineralvarie- 
taten;  Ber.  Ak.  Wien,  Ixix.,  1874  (Am.  J.  Sci.,  III.,  viii.,  255). 

Hankel.  Ueber  die  thermo-elektrischen  Eigenschaften  des  Boracites  ;  Sachs.  Ges.  Wiss., 
vi.,  151,  1865;  ibid.,  viii.,  323,  1866;  Topaz,  ix.,  1870,  359;  10  Abhandlung,  1872,  24;  cal- 
cite,  beryl,  etc.,  1876. 

On  MAGNETISM  reference  may  be  made  to  Faraday  (Experimental  Researches) ;  Tyndall, 
Phil.  Mag.  ;  Knoblauch  and  Tyndall,  Pogg.,  Ixxxi.,  481,  498  ;  Ixxxiii.,  384  ;  Pfliicker,  Pogg., 
Ixxii.,  315;  Ixxvi.,  576;  Ixxvii.,  4±7;  Ixxxvi.,  1;  Grailich  u.    von  Lang,   Ber.   Ak.,   Wien,f 
xxxii.,  43  ;  xxxiii.,  439,  etc.,  etc. 


YI.  TASTE  AND  ODOR 

In  their  action  upon  the  senses  a  few  minerals  possess  taste,  and  others 
under  some  circumstances  give  off  odor. 

TASTE  belongs  only  to  soluble  minerals.     The  different  kinds  of  taste 
adopted  for  reference  are  as  follows  : 
^  1.  Astringent ;  the  taste  of  vitriol. 

2.  Sweetish  astringent  ;  taste  of  alum. 

3.  Saline  /  taste  of  common  salt. 

4.  Alkaline  ;  taste  of  soda. 

5.  Cooling ;  taste  of  saltpeter. 

6.  Bitter  •  taste  of  epsom  salts. 

7.  Sour  ;  taste  of  sulphuric  acid. 

^Oeo». — Excepting  a  few  gaseous  and  soluble  species,  minerals  in  the  dry 
unchanged  state  do  not  give  off  odor.  By  friction,  moistening  with  the 
breath,  and  the  elimination  of  some  volatile  ingredient  by  heat  or  acids, 
odors  are  sometimes  obtained  which  are  thus  designated : 

1.  Alliaceous  /  the  odor  of  garlic.     Friction  of  arsenical  iron  elicits  this 
odor ;  it  may  also  be  obtained  from  arsenical  compounds,  by  means  of  heat. 

2.  Horse-radish  odor  ;  the  odor  of  decaying  horse-radish.     This  odor  is 
strongly  perceived  when  the  ores  of  selenium  are  heated. 

3.  Sulphureous  /  friction  elicits  this  odor  from  pyrite  and  heat  from 
many  sulphides. 

4.  Bituminous  ;  the  odor  of  bitumen. 

5.  Fetid;  the  odor  of  sulphuretted  hydrogen  or  rotten  eggs.     It  is  eli- 
cited by  friction  from  some  varieties  of  quartz  and  limestone. 

6.  Argillaceous  ;  the  odor  of  moistened  clay.     It  is  obtained  from  ser- 


168  PHYSICAL    CHARACTERS    OF    MINERALS. 

pentine  and  some  allied  minerals,  after  moistening  them  with  the  breath ; 
others,  as  pyrargillite,  afford  it  when  heated. 

The  FEEL  is  a  character  which  is  occasionally  of  some  importance  ;  it  is 
said  to  be  smooth  (sepiolite),  greasy  (talc),  harsh,  or  meagre,  etc.  Some 
minerals,  in  consequence  of  their  hygroscopic  character,  adhere  to  the  tongue, 
when  brought  in  contact  with  it. 


PA.RT    II. 

CHEMICAL  MINERALOGY. 


MINERALS  are  either  the  uncombined  elements  in  a  native  state,  or  com- 
pounds of  these  elements  formed  in  accordance  with  chemical  laws.  It  is 
the  object  of  Chemical  Mineralogy  to  determine  the  chemical  composition 
of  each  species  ;  to  show  the  chemical  relations  of  different  species  to  each 
other  where  such  exist ;  and  also  to  explain  the  methods  of  distinguishing 
different  minerals  by  chemical  means.  It  thus  embraces  the  most  import- 
ant part  of  Determinative  Mineralogy. 


CHEMICAL  CONSTITUTION  OF  MINERALS. 

In  order  to  understand  the  chemical  constitution  of  minerals,  some 
knowledge  of  the  fundamental  principles  of  Chemical  Philosophy  is 
required  ;  and  these  are  here  briefly  recapitulated. 

Chemical  elements. — Chemistry  recognizes  sixty-four  substances  which 
cannot  be  decomposed,  or  divided  into  others,  by  any  processes  at  present 
known;  these  substances  are  called  the  chemical  elements.  Of  these 
oxygen,  hydrogen,  and  nitrogen  are  fixed  gases ;  chlorine  and  fluorine  are 
generally  gases,  but  may  be  condensed  to  the  liquid  state  ;  bromine  is  a 
volatile  liquid ;  and  the  rest,  under  ordinary  conditions,  quicksilver  excepted, 
are  solids.  Of  these  last  carbon,  phosphorus,  arsenic,  sulphur,  boron,  (tel- 
lurium), selenium,  iodine,  silicon,  generally  rank  as  non-metallic  elements, 
and  the  others  as  metallic. 

Molecules  ;  Atoms. — By  a  molecule  is  understood  the  smallest  portion  of  a 
substance  which  possesses  all  the  properties  of  the  matter  itself ;  it  is  the 
smallest  division  into  which  the  substance  can  be  divided  without  loss  or 
change  of  character.  The  molecule  of  water  is  the  smallest  conceivable 
particle  which  can  exist  alone,  and  which  has  all  the  properties  of  water. 
An  atom  is  the  smallest  mass  of  each  element  which  enters  into  combina- 
tion with  others  to  form  the  molecule.  Thus  two  chemical  units,  or  atoms, 
of  hydrogen  unite  with  one  atom  of  oxygen  to  form  the  physical  unit,  or 
molecule,  of  water. 

Atomic  weights. — The  relative  weights  of  the  chemical  units,  or  atoms, 
of  the  different  elements  are  their  atomic  weights.  For  the  sake  of  uni- 


170  CHEMICAL   MINERALOGY. 

formity  the  atom  of  hydrogen,  the  lightest  of  all  the  elements,  has  been 
adopted  as  the  standard  or  unit.  The  absolute  weight  of  the  atoms  cannot 
be  determined  ;  but  their  relative  weight  can  in  many  cases  be  fixed  beyond 
question.  When  the  elements  are  gases,  or  form  gaseous  compounds,  the 
atomic  weights  are  determined  directly.  Thus  in  hydrochloric  acid  gas 
there  are  equal  volumes  of  hydrogen  and  chlorine,  or,  chemically  expressed, 
one  atom  of  hydrogen  combines  with  one  atom  of  chlorine  ;  by  analysis  it 
is  found  that  in  100  parts  there  are  2-74  by  weight  of  hydrogen,  and  97'26 
of  chlorine  ;  hence  if  hydrogen  be  taken  as  the  unit,  the  atomic  weight  of 
chlorine  is  35-5,  since  2-94  :  97'26  =  1  :  35-5. 

Where  the  elements,  or  their  compounds,  are  not  gases,  the  atomic  weights 
are  determined  more  or  less  indirectly,  and  are  sometimes  not  entirely  free 
from  doubt.  The  analysis  of  rock-salt  gives  us,  in  100  parts,  60-68  parts  of 
chlorine,  and  39 '32  parts  of  sodium  ;  now  if,  as  is  believed,  the  number  of 
units  of  each  element  involved  is  the  same,  or  in  other  words,  if  the  mole- 
cule consists  of  one  atom  each  of  chlorine  and  sodium,  then  the  atomic 
weights  will  be  as  60-68  :  39-32  ;  or  35-5  :  23,  since  that  of  chlorine  =  35-5. 
Hence  the  atomic  weight  of  sodium  is  23,  when  referred,  like  chlorine,  to 
that  of  hydrogen  as  the  unit.  There  is  an  assumption  in  such  cases  as  to 
the  number  of  units  of  each  element  involved  which  may  introduce  doubt, 
so  that  other  methods  are  applied  which  need  not  be  here  detailed. 

The  following  table  gives  the  atomic  weights  of  the  elements.  The  symbols 
used  to  represent  an  atom  of  each  element  are  shown  in  the  table ;  in  most 
cases  they  are  the  initial  letter  or  letters  of  the  Latin  name.  When  more  than 
one  atom  is  involved  in  the  formation  of  a  compound,  it  is  indicated  by  a 
small  index  number  placed  below,  to  the  right :  as  Sb2O3,  which  signifies  2 
of  antimony  to  3  of  oxygen.  The  quantity  by  weight  of  any  element  enter- 
ing into  a  compound  is  always  expressed  either  by  the  atomic  weight  or 
some  multiple  of  it ;  hence  the  atomic  weights  are  strictly  the  combining 
weights  of  the  different  elements. 


ATOMIC  WEIGHTS. 


Aluminum 

Al 

27-3 

Cobalt 

Co 

59 

Antimony 

Sb 

122 

Columbium  (Niobium) 

Cb    (Nb) 

94 

Arsenic 

As 

75 

Copper 

Cu 

63-4 

Barium 

Ba 

137 

Didymium* 

D 

96-5 

Bismuth 

Bi 

208 

Erbium 

E 

112-6 

Boron 

B 

11 

Fluorine 

F 

19 

Bromine 

Br 

80 

Gallium 

Ga 

Cadmium 

Cd 

112 

Glucinum 

G 

9 

Caesium 

Cs 

133 

Gold 

Au 

196 

Calcium 

Ca 

40 

Hydrogen 

H 

•      1 

Carbon 

C 

12 

Indium 

In 

113-4 

Cerium* 

Ce 

92 

Iodine 

I 

127 

Chlorine 

Cl 

35-5 

Iridium 

Ir 

198 

Chromium 

Cr 

52       Iron 

Fe 

56 

*  By  the  determination  of  the  specific  heats  of  cerium,  didymium,  and  lanthanum,  Dr. 
Hillebrand  has  shown  recently  that  the  oxides  of  the  three  metals  are  sesquioxides  (Ce203, 
Di2O3,  La203),  and  corresponding  to  them  the  atomic  weights  should  be  Ce  =  138,  Di  = 
144-8,  La  =  189.  (Pogg.  Ann.,  clviii.,  71,  1876.) 


CHEMICAL   CONSTITUTION    OF   MINERALS.  171 


Lanthanum  La  92 '5 

Lead  Pb  207 

Lithium  Li 

Magnesium  Mg  24 

Manganese  Mn  55 

Mercury  Hg  200 

Molybdenum  Mo  96 

Nickel  Ni  59 

Nitrogen  N  14 

Osmium  Os  200 

Oxygen  O  16 

Palladium  Pd  106 

Phosphorus  P  31 

Platinum  Pt  198 

Potassium  K  39 

Rhodium  Bo    •  104 

Rubidium  Rb  85 '4 

Ruthenium  Ru  104 


Selenium  Se  79 

Silver  Ag  108 

Silicon  Si  28 

Sodium  Na  23 

Strontium  Sr  88 

Sulphur  S  H2 

Tantalum  Ta  182 

Tellurium  Te  128 

Thallium  Tl  204 

Thorium  Th  231 

Tin  Sn  118 

Titanium  Ti  50 

Tungsten  W  184 

Uranium  240 

Vanadium  V  51  *  4 

Yttrium  Y  61 '7 

Zinc  Zn  65 

Zirconium  Zr  90 


Atomicity  /  Quantivalence. — The  combining  power  of  each  element  is 
measured  by  the  number  of  hydrogen  atoms  with  which  it  combines  in 
forming  a  chemical  compound.  In  hydrochloric;  acid  (HC1),  one  atom  of 
hydrogen  combines  with  one  of  chlorine ;  in  water  (I12O),  two  atoms  of 
hydrogen  combine  with  one  of  oxygen ;  in  ammonia  (H3N),  three  atoms  of 
hydrogen  combine  with  one  of  nitrogen ;  and  in  marsh  gas  (H4C),  four 
atoms  of  hydrogen  are  required  to  enter  into  combination  with  one  carbon 
atom. 

By  the  examination  of  compounds  of  all  the  elements  we  are  able  to  fix 
the  combining  power,  or  quantivalence,  of  each,  expressed  in  hydrogen 
units.  All  those  elements  which  combine  with  one  atom  of  hydrogen,  or 
an  element  which  (like  chlorine)  has  the  same  quantivalence,  are  called 
monads  •  those  which  require  two  of  hydrogen,  or  two  other  monad  atoms, 
in  forming  the  compound,  are  called  dyads  ;  those  uniting  with  three  atoms 
of  hydrogen  are  called  triads  ;  and  similarly  tetrads,  pentads,  hexads,  and 
hcptads. 

The  adjective  terms  univalent,  bivalent,  trivalent,  quadrivalent,  etc.,  are 
also  employed  with  similar  meaning.  Atoms  having  the  same  degree  of 
quantivalence  are  said  to  be  equivalent;  this  is  true  of  Na  and  K,  both 
monads,  and  they  may  replace  eadi  other  in  similar  compounds ;  but  it 
requires  two  sodium  atoms  to  be  equivalent  to  one  calcium  atom,  since  the 
latter  is  a  dyad. 

The  degree  of  quantivalence  may  vary  for  many  of  the  elements  in 
different  compounds ;  for  example,  in  FeO  or  FeS,  iron  (Fe)  is  bivalent, 
since  it  satisfies  or  is  combined  with  simply  a  dyad  ;  in  FeS2,  it  is  quadri- 
valent, since  it  is  united  to  two  ajoms  of  a  dyad ;  and,  similarly,  in  [Fe2]O3 
it  is  sexivalent  (for  the  double  atom). 

Perissads  /  Artiads. — Those  elements  whose  atoms  have  an  odd  quanti- 
valence (I,  III,  Y,  or  VII),  are  called  perissads  •  those  whose  quantivalence 
is  even  (II,  IY,  VI)  are  called  artiads.  These  terms,  perissad  and  artiad, 
are  derived  from  Trepicra-os  and  apnos,  the  words  for  odd  and  even  in 
ancient  arithmetic.  The  following  table  gives  the  division  of  the  ele- 
ments into  these  two  classes,  and  shows,  also,  the  quantivalence  of  each  ele- 
ment : 


172 


CHEMICAL   MINEKALOGY. 


PERISSADS. 


ARTIADS. 


Monads  :  —                                I 

Dyads  :  — 

Tetrad*  :— 

Hydrogen. 

Oxygen. 

Carbon, 

II,  IV. 

Sulphur,      II,  IV,  VI. 

Silicon. 

Fluorine. 

Selenium,    II,  IV,  VI. 

Titanium, 

II,  IV. 

Chlorine,   I,  III.  V,  VII. 

Tellurium,  II,  IV,  VI. 

Tin, 

II,  IV. 

Bromine,   I,  III,  V,  VII. 

Iodine,       I,  III,  V,  VII. 

Calcium,      II,  IV. 

Thorium, 

Strontium,  II,  IV. 

Zirconium. 

Lithium. 

Barium,        II,  IV. 

Sodium,          I,  III. 

Platinum, 

II,  IV. 

Potassium,     I,  III,  V. 

Magnesium. 

Palladium, 

II,  IV. 

Rubidium. 

Zinc. 

Caesium. 

Cadmium. 

Lead, 

II,  IV. 

Indium. 

Silver,            I,  III. 

Glucinum. 

1 

Thallium,       I,  III. 

Yttrium. 

Hexads  :  — 

Cerium. 

Molybdenum 

,  II,  TV,  VI. 

Triads  :— 

Lanthanum. 

Tungsten, 

IV,  VI. 

Nitrogen,        I,  III,  V. 

Didymium. 

Phosphorus.  I,  III,  V. 

Erbium. 

Ruthenium, 

II,  IV,  VI. 

Arsenic,           I,  III,  V. 
Antimony,           III,  V. 
Bismuth,            III,  V. 

Mercury    [Hg2]n,  11. 
Copper      [Cu2]u,  II. 

Rhodium, 
Iridium, 
Osmium, 

II,  IV,  VI. 
11,  IV,  VI. 
II,  IV,  VI. 

Boron. 

Aluminum, 

IV,  [A19]VI. 

Chromium, 

II,  IV,  VI. 

Gold,               I,  III. 

Manganese, 

II,  IV,  VI. 

Pentads  :  — 

Iron, 

II,  IV,  VI. 

Columbium. 

Cobalt, 

II,  IV. 

Tantalum. 

Nickel, 

II,  IV. 

Uranium, 

II,  IV. 

Vanadium,          III,  V. 

The  general  divisions  of  chemical  compounds  now  accepted  are  as  fol- 
lows. 

1.  Binaries,  where  the  atoms  are  directly  united.     Examples  are  given 
by  the  compounds  of  a  positive  (basic)  element  with  oxygen  (Na2O,  CaO, 
CO2),  called   oxides ;   those  with  sulphur,  chlorine,  bromine,  iodine,  etc., 
called  sulphides,  chlorides,  etc.     Binary  compounds  of  a  negative  element 
with  hydrogen  (as  HC1,  HBr)  form  acids. 

2.  Ternaries,  where  the  atoms  are  united  by  means  of  a  third  atom,  as 
oxygen,  sulphur,  etc.,  as  CaSO4,  Mg2SiO4,  etc. 

Among  minerals  there  are  three  classes  of  compounds :  (1)  The  Native 
Elements  ;  (2)  Binary  compounds,  including  the  sulphides,  oxides,  chlorides, 
iodides,  fluorides  ;  (3)  Ternary  compounds,  including  sulph-arsenites,  etc., 
hydrates  (hydrated  oxides),  silicates,  mostly  salts  of  the  acids  Il4SiO4  and 
H2SiO3,  tantalates,  colurnbates,  phosphates,  arsenates,  sulphates,  chromates, 
carbonates,  etc.  The  full  enumeration  of  these  compounds,  with  their  gen- 
eral chemical  formulas,  are  given  in  the  synopsis  which  precedes  the 
Descriptive  Mineralogy. 

The  position  of  water  in  the  composition  of  minerals. — Many  minerals 
lose  water,  especially  upon  the  application  of  heat.  With  some  of  these  it 
is  given  off  upon  mere  exposure  to  dry  air  at  ordinary  temperature,  and 
such  crystals  are  said  to  effloresce  /  others  lose  water  when  they  are  placed 
in  a  desiccator  over  sulphuric  acid,  or  when  they  are  subjected  to  a  slightly 


CHEMICAL   CONSTITUTION   OF   MINERALS.  173 

elevated  temperature;  with  others,  again,  a  greater  heat  is  required;  and 
with  a  few  silicates  water  is  yielded  only  upon  long  continued  heating  at  a 
very  high  temperature.  It  is  evidently  possible  that  either,  (1)  the  mineral 
contains  water  as  such,  or  (2)  the  water  is  formed  by  the  process  of  decom- 
position caused  by  the  application  of  heat.  In  the  cases  first  mentioned, 
where  water  is  readily  given  off,  it  is  believed  that  the  water  actually  exists 
as  such  in  the  compound.  It  is  found  that  many  salts  take  up  water  when 
they  crystallize,  and  in  some  cases  the  amount  of  water  depends  upon  the 
temperature  at  which  the  salt  is  formed  ;  this  water  is  called  water  of 
crystallization.  For  example:  manganous  sulphate  has  three  definite 
amounts  of  this  water  of  crystallization,  according  to  the  temperature  at 
which  it  has  been  formed.  When  crystallized  below  7°,  its  composition  is 
MiiSO4  +  7HaO;  between  7°  and  20°,  MnSO4  +  5H2O  ;  and  between  20? 
and  30°,  Mil  SO4  +  411,0. 

In  those  cases  where  a  very  high  temperature  is  required  to  make  a  loss 
of  water,  it  is  quite  certain  the  wrater  has  no  place  as  such  in  the  original 
constitution,  but,  on  the  contrary,  that  the  mineral  contains  basic  hydrogen, 
replacing  the  other  basic  elements.  In  some  cases,  where  part  of  the  water 
is  yielded  at  a  low  and  the  rest  at  a  very  high  temperature,  this  shows  that 
a  difference  exists  in  regard  to  the  part  which  the  water  plays  in  the  two 
cases  ;  for  example,  crystallized  sodium  phosphate  yields  readily  24  equiva- 
lents of  water,  while  the  remaining  1  molecule  is  given  off  only  at  a  tem- 
perature between  300°  and  400°  ;  from  this  it  is  concluded  that  in  the 
latter  case  the  elements  forming  the  water  exist  actually  in  the  salt,  and 
that  its  composition  is  : 


The  part  played  by  the  water  in  the  silicates  is  in  most  cases  still  unde- 
cided, though  in  many  species  the  hydrogen  is  undoubtedly  basic.  The 
latter  is  doubtless  true  of  many  of  the  so-called  hydrous  silicates.  The  views 
commonly  held  in  regard  to  them  will  be  gathered  from  the  descriptive  part 
of  this  work. 

Chemical  formulas  for  minerals.  —  A  chemical  formula  expresses  the 
relative  amounts  of  the  different  elements  present  in  the  compound,  in 
terms  of  their  atomic  weights  —  or,  in  other  words,  more  strictly  the  number 
of  atoms  of  each  element  in  a  given  molecule  with  or  without  the  expression 
of  their  probable  grouping. 

Empirical  formulas  simply  state  in  the  briefest  form  the  result  of  the 
analysis,  giving  the  number  of  atoms  of  each  element  present  without  any 
theoretical  considerations.  For  example,  the  empirical  formula  of  epidote 
is  Si6Al3Ca4H2026. 

The  object  of  the  rational  formulas  is  to  express  not  only  the  number  of 
atoms  of  each  element  present,  but  also  their  probable  method  of  grouping, 
and  relation  to  each  other,  in  the  molecule.  These  are  called  typical  for- 
mulas when  the  attempt  is  made  to  arrange  the  atoms  in  accordance  with  the 
type  of  wrater,  or  some  other  type. 

In  the  rational  formulas  of  the  old  chemistry  the  oxygen  (or  sulphur) 
was  apportioned  to  the  several  elements,  according  to  their  combining 
power,  and  the  basic  and  acid  oxides,  or  sulphides,  thus  obtained  were  writ- 
ten consecutively.  For  example,  the  formula  of  wollastonite  (calcium  sili- 


174 


CHEMICAL    MINERALOGY. 


cate),  according  to  the  old  dnalistic  method,  was  written  CaO,  SiO2,  and 
of  anhydrite  (calcium  sulphate),  CaO,  SO3.  The  principles  of  the  new 
chemistry  have  set  aside  these  rational  formulas ;  but  as  others  consistent 
with  the  new  principles  now  adopted  have  not  in  all  cases  been  accepted, 
it  is  customary  to  give  the  formulas  of  minerals  empirically.  For  those 
above  the  empirical  formulas  are  CaSiO3  and  CaSO4. 

Relation  between  the  old  and  new  systems. — The  points  of  difference 
between  the  old  and  new  chemistry  have  already  been  hinted  at.  The 
principal  changes  which  have  been  introduced  by  the  latter  are  :  (1)  The 
doubling  of  all  the  atomic  weights,  except  those  of  the  monad  elements, 
and  also  of  bismuth,  arsenic,  antimony,  nitrogen,  phosphorus,  and  boron, 
whose  oxides  are  now  written  Bi2O3,  instead  of  BiO3,  etc.  Corresponding 
to  this  change,  binary  compounds  involving  the  monad  elements  are  writ- 
ten :  H2O  instead  of  HO,  Na2O  for  NaO,  Na2S,  etc.,  also  CaCl2  instead  CaCl, 
SiF4  instead  of  SiF2,  and  so  on.  (2)  The  method  of  viewing  the  composi- 
tion of  ternary  compounds — these  being  now  regarded  not  as  compounds 
of  an  oxide  and  a  so-called  acid,  but  as  compounds  for  the  most  part  of 
the  several  elements  concerned,  and  hence  a  metal  in  a  compound  is 
believed  to  be  replaced  by  another  metal,  not  one  oxide  by  another.  Hence 
we  say  calcium  carbonate,  or  carbonate  of  calcium  instead  of  carbonate  of 
lime,  and  write  the  formula  CaCO3,  not  CaO,  CO2 ;  and  so  in  the  other 
cases. 

Replacing  power  of  the  different  elements. — It  has  been  mentioned 
that  the  replacing  power  of  the  elements  is  in  proportion  to  their  combining 
power,  that  is,  to  their  quantivalence.  For  example,  one  atom  of  Mg  or 
of  Ba  may  replace  one  atom  of  Ca,  all  being  dyads  ;  but  two  atoms  of  Na 
(monad)  are  required  to  replace  one  of  Ca ;  similarly  three  dyad  atoms  are 
equivalent,  or  may  replace,  one  hexad  atom,  thus,  3Ca  —  [A12]. 

The  relation  of  the  different  oxides  may  be  understood  from  the  follow- 
ing scheme,  in  which  the  above  principle  is  made  use  of.  The  line  A 
below  contains  the  different  kinds  of  oxides.  B  the  same  divided  each  by 
its  number  of  atoms  of  oxygen  (that  is,  severally,  for  the  successive  terms, 
by  1,  3,  2,  5,  3,  7,  4),  by  which  division  they  are  reduced  to  the  protoxide 
form.  C  the  basic  elements  alone : 

A  KO  R2O3  KO2  K2O5  RO3  R2O7  RO4 
B  RO  R*O  R*O  R*O  R*O  R'O  R*O 
C  R  R*  R*  E*  E*  E*  E* 

According  to  the  above  law  the  R,  R*,  R*,  etc.,  in  the  last  line,  are  mutu- 
ally replaceable,  1  for  1,  though  varying  in  atomic  weight  from  1  to  J. 
They  represent  different  states  in  which  elements  may  exist,  and  have,  to  a 
certain  extent,  independent  element-like  relations.  In  some  cases,  as  in 
iron,  four  of  these  states  are  represented  in  a  single  element,  the  compounds 
(1)  FeO,  FeS,  (2)  Fe2O3,  (3)  FeS2,  (4)  FeO3,  containing  this  metal  in  four 
states  Fe,  Fe*,  Fe},  Fe*. 

The  use  of  the  fractions  can  be  avoided  by  multiplying,  instead  of  divid- 
ing, thus,  Fe*  of  Fe2O3  replaces  Fe  of  FeO,  we  might  have  said,  2Fe  of 
Fe2O3  replaces  3Fe  of  FeO  (Fe2O3,  Fe8O8),  and  so  for  the  others. 

These  different  states  of  the  elements  are  best  designated  in  the  symbols 


CHEMICAL    CONSTITUTION    OF   MINEEALS.  175 

by  the  Greek  letters  a,  /3,  etc.,  thus  avoiding  all  confusion.     The  above 
lines  A,  B,  C  then  become 


A         aRO        3/3RO        27RO        5SRO        3eRO        7?RO 

B          aRO          PRO          yRO          3RD          eRO          JRO          7?RO 

C  aR  £R  7R  SR  eR  fR  7?R 


By  means  of  this  system  all  the  different  oxides  may  be  reduced  to  the 
common  protoxide  form,  and  thus  the  true  relations  of  the  silicates  may  be 
clearly  expressed.  This  is  exhibited  in  the  formulas  for  the  silicates  given 
in  Dana's  System  of  Mineralogy  (1868). 

Calculation  of  a  formula  from  an  analysis.  —  The  result  of  an  analysis 
gives  the  proportions,  in  a  hundred  parts  of  the  mineral,  of  either  the  ele- 
ments themselves,  or  of  their  oxides  or  other  compounds  obtained  in  the 
chemical  analysis.  In  order  to  obtain  the  atomic  proportions  of  the  ele- 
ments :  Divide  the  percentages  of.  the  elements  by  the  respective  ATOMIC 
WEIGHTS  ;  or,  for  those  of  the  oxides  :  Divide  the  percentage  amounts  of 
each  by  their  MOLECULAR  WEIGHTS  ;  then,  find  the  simplest  ratio  in  whole 
nujnbersfor  the  numbers  thus  obtained. 

Examples.  —  An  analysis  of  bournonite  from  Meiseberg  gave  Rammels- 
berg  :  Lead  (Pb)  42'8S,  copper  (Cu)  13-06,  antimony  (Sb)  24-34,  and  sul- 
phur (S)  19*76  =  100-04:.  Dividing  each  amount  by  its  atomic  weight  we 
obtain  : 


The  atomicratiois  hence:—  Pb  :  Cu  :  Sb  :  S  =  '207  :  -206  :  -217  :  '6175  ; 
that  is,  1-005  :  1  :  1-053  :  2-998,  or  in  whole  numbers,  1:1:1:3.  .The 
empirical  formula  is  consequently  CuPbSbS3. 

An  analysis  of  epidote  from  Untersulzbach  gave  Ludwig  : 

SiO2        A1O3        FeO3        FeO        CaO        H2O 

37-83       22-63         15*02        0-93         23-27       2-05  =  101-73. 

From  the  results  of  the  analysis  given  in  this  form,  the  percentage 
amount  of  each  element  may  be  calculated  in  the  usual  way  ;  we  obtain  : 
Si  17-65,  Al  12-06,  Fe  10-51,  FeO  0-72,  Ca  16-62,  II  0.23,  O  43-64.  The 
number  of  atoms  of  each  element  may  be  calculated  from  the  last  given 

percentages  by  dividing  each  by  the  atomic  weight,  that  is"  -     -  =  -630 

12*06 

for  Si,  =  0-22  for  Al  (=  A12),  etc.  Or,  the  percentage  amounts  of  eacli 

55 

oxide  may  be  divided  by  its  molecular  weight,  and  the  result  will  be  the  same  ; 

37*83 
for  SiO2,  the  molecular  weight  is  60  (28  +  2x16),  hence,  -     -  =  '630  as 

22-63 
before  ;  also  for  Al,  103  (=  2  x  27'5  +  3  x  16),  and  --  =  0-22,   etc.      The 

atomic  proportions  thus  obtained  are  : 


176  CHEMICAL    MINERALOGY. 

Si  Al  Fe  Fe  Ca  H  O 

0-630        0-220        0-094        0-013        0415         0-230        2*727,  or  simply 


0-428 

6  2-99  4-07  2-2          25-79,    or  again, 

63  4  2  26. 

The  empirical  formula  is  consequently  Si6Al3Ca4H2O26.  As  in  the  above 
case,  it  is  necessary,  when  very  small  quantities  only  of  certain  elements 
are  present,  to  neglect  them  in  the  final  formula,  reckoning  them  in  with 
the  elements  which  they  replace,  that  is,  with  those  of  the  same  quanti  va- 
lence. The  degree  of  correspondence  -between  the  analysis  and  the  formula 
deduced,  if  the  latter  is  correctly  assumed,  depends  entirely  upon  the  accuracy 
of  the  former. 

Quantivalent  Ratio.  —  In  the  chemical  constitution  of  most  minerals 
there  exists  a  strong  distinction  between  the  basic  and  acidic  elements,  and 
this  relation,  in  the  case  of  substances  of  complex  character,  is  often  fixed 
when  otherwise  the  composition  is  exceedingly  varied.  In  the  dualistic 
formulas  of  the  old  chemistry  this  relation  was  expressed  in  the  "  oxygen- 
ratio"  which  gave  the  ratio  between  the  number  of  oxygen  atoms  belong- 
ing respectively  to  the  bases,  protoxide  and  sesquioxide,  and  to  the  acid. 
The  expression,  "oxygen-ratio,"  is  not  in  harmony  with  the  present  method 
of  viewing  chemical  compounds,  and  the  term  has  consequently  been,  to 
some  extent,  abandoned  ;  the  same  relation,  however,  between  the  different 
classes  of  elements  still  exists,  but  the  ratio  must  be  regarded  as  that  exist- 
ing between  the  total  quanti  valences  of  each  group  of  elements,  and  hence 
may  be  called  the  QUANTIVALENT  RATIO.  * 

The  old  formula  for  all  the  members  of  the  garnet  family  is  3R,  K,  3Si 
—  3RO,  RO3,  3SiO2,  and  the  oxygen  ratio  for  &  :  ii  :  Si  =  1  :  1  :  2,  or  for 
bases  to  silica,  1  :  1.  Here  R  may  be  either  Ca,  Mg,  Fe,  Mn,  or  Cr,  and  R 
either  Al,  Fe,  Or.  This  formula,  however,  written  according  to  the  new 
system  (the  quantivalence  being  expressed  by  Roman  numerals  over  the 
symbols),  is: 

II    VI  IV    II  II    VI 

R3RSi012  ;  or 


to  indicate  that  the  oxygen  is  regarded  as  all  linking  oxygen.  The  ratio 
of  the  total  quantivalences  for  each  class  of  elements,  dyads  and  hexads 
(basic),  and  the  tetrad  silicon  (acidic),  is:  —  3  xll  :  YI  :  3  xIY,  or.  Q.  ratio 
for  R  :  R  :  Sif  =  6  :  6  :  12,  that  is,  1  :  1  :  2. 

The  same  ratio  for  (R-HB)  :  Si  =  1  :  1,  both  of  which  are  identical  with 
the  previously  given  oxygen  ratio. 

*  This  relation  was  brought  out  by  Prof.  Dana  in  1867  (Am.  J.  Sci.,  xliv.,  89,  252,  398), 
and  it  forms  the  basis  of  all  the  formulas,  according1  to  the  new  system,  in  Dana's  System  of 
Mineralogy,  1868.  Prof.  Cooke  has  discussed  the  same  subject  (Am.  J.  Sci.,  II.,  xlvii.,  380, 
1869),  he  calls  the  ratio,  the  Atomic  Ratio  ;  the  latter  term,  however,  is  generally  used  in  a 
different  sense,  hence  the  expression  Quantivalent  Ratio  employed  here. 

f  Throughout  this  work  the  letter  R,  unless  otherwise  indicated,  represents  a  bivalent 
metal,  and  ft  either  Fe,  Al,  -Gr,  Mn,  where  the  quantivalence  of  the  double  atom  is  six.  In 
a  few  cases,  to  indicate  further  relations,  the  sign  of  the  quantivalence  is  sometimes  employed. 


DIMORPHISM ISOMORPHISM.  177 

Thus  the  oxygen  ratio  of  the  old  system  becomes  the  quantivalent  ratio 
of  the  new,  "  a  term,  too,  which  has  a  wider  meaning  and  bearing  than  that 
which  it  replaces."  This  principle  of  the  ratio  between  the  total  quanti- 
valences  is  an  important  one,  and  fundamental  in  the  character  of  chemical 
compounds.  This  is  well  shown  in  the  example  here  given,  where,  for  a 
family  of  minerals  of  so  varied  composition  as  the  garnets,  it  remains  con- 
stant in  all  varieties.  Its  importance  is  even  more  marked  in  the  many 
silicates  where  R  replaces  3R  (as  in  spodumene  in  the  pyroxene  family). 

The  quantivalent  ratio  is  obtained  by  multiplying  the  quantivalence  of 
each  class  of  elements  present  by  their  number  of  atoms;  or  by  dividing 
the  percentage  amount  of  each  element  by  the  atomic  weight  and  multiply 
by  its  quantivalence.  When  the  basic  or  acid  oxides  are  given,  divide 
the  percentage  amount  of  each  by  the  molecular  weight,  and  multiply  as 
before  by  the  number  expressing  the  quantivalence,  and  the  result  is  the 
total  quantivalence  for  the  given  element. 


DIMORPHISM.     ISOMORPHISM. 

A  chemical  compound,  which  crystallizes  in  two  forms  genetically  dis- 
tinct, is  said  to  be  dimorphous;  if  in  three,  trimorphous,  or  in  general 
pleomorplious.  The  phenomenon  is  called  DIMORPHISM,  or  PLEOMORPHISM. 

On  the  other  hand,  chemical  compounds,  which  are  of  dissimilar  though 
analogous  composition,  are  said  to  be  isomorphous  when  their  crystalline 
forms  are  identical,  or  at  least  very  closely  related  (sometimes  called  homoeo- 
morphous).  This  phenomenon  is  called  ISOMORPHISM. 

An  example  of  pleomorphism  is  given  by  the  compound  calcium  carbon- 
ate (CaCO3),  which  is  trimorphous :  appearing  as  calcite,  as  aragonite,  and 
as  baryto-calcite.  As  calcite*  it  crystallizes  in  the  rhombohedral  system, 
and,  unlike  as  its  many  crystalline  forms  are,  they  may  be  all  referred  to 
the  same  fundamental  rhombohedron,  and,  what  is  more,  they  have  all  the 
same  cleavage  and  the  same  specific  gravity  (2'7),  and,  of  course,  the  same 
optical  characters.  As  aragonite,  calcium  carbonate  appears  in  orthorhom- 
bic  crystals,  whose  optical  characters  are  entirely  different  from  those  of 
calcite,  as  will  be  understood  from  the  explanations  made  in  the  preceding 
chapter.  Moreover,  the  specific  gravity  of  aragonite  (2*9)  is  higher  than 
that  of  calcite  (2* 7).  Again,  as  baryto-calcite,  calcium  carbonate  crystal- 
lizes in  a  monoclinic  form. 

The  explanation  of  the  phenomenon  of  pleomorphism  in  this  case— and 
an  analogous  explanation  must  answer  fur  all  such  cases — is  to  be  found, 
not  as  was  once  proposed  in  a  slight  variation  of  chemical  composition,  but 
in  the  different  conditions  in  which  the  same  compound  has  been  formed. 
Thus  Rose  has  shown  that  the  calcium  carbonate  precipitated  from  a  solu- 
tion by  the  alkaline  carbonates  in  the  cold  has  the  form  of  calcite,  whereas, 
if  the  precipitation  takes  place  at  a  temperature  of  100°  C.,  it  takes  the 
form  of  aragonite.  Moreover,  he  found  that  aragonite  on  heating  fell  to 
powder,  and  though  no  loss  of  weight  took  place,  the  specific  gravity  (^'9) 
became  that  of  calcite  (2'7). 

Many  other  examples  of  pleomorphism  may  be  given  :  Silica  (SiO2)  is 
trimorphous ;  appearing  as  quartz,  rhombohedral,  G  =  2*66  ;  as  ti'idymite, 
12 


178  CHEMICAL   MINEEALOGY. 

hexagonal,  G  ==  2*3  ;  and  as  asmanite,  orthorhombic,  G  =  2*24.  Titanic 
oxide  (TiO2)  is  also  trimorphous,  the  species  being  called  rutile,  tetragonal 
(c  —  -6442),  G  =  4-25  ;  octahedrite  (c  —  1'773),  G  =  3-9  ;  and  IrooUte, 
orthorhombic  or  monoclinic,  G  =  4*15.  Carbon  appears  in  two  forms,  in 
diamond  and  graphite.  Other  familiar  examples  are  pyrite  and  marcasite 
(FeS2) ;  acanthi  te  and  argentite  (Ag2S) ;  sphalerite  and  wiirtzite  (ZnS) ; 
sulphur  natural,  orthorhombic,  if  artificial  and  crystallizing  from  a  molten 
condition,  monoclinic.  The  relation  in  form  of  the  species  mentioned, 
and  also  of  those  of  other  dimorphous  groups,  will  be  found  in  Part  III., 
Descriptive  Mineralogy. 

Isomorphism  is  well  illustrated  by  the  group  of  rhombohedral  carbonates, 
with  the  general  formula  RCO8.  Here  E,  may  be  Ca,  Mg,  Fe,  Mn,  or  Zn  ; 
or  further,  in  the  same  species,  the  E,  may  be  represented  by  both  Ca  and 
Mg  in  varying  proportions,  as  remarked  on  the  following  page,  or  both  Ca 
and  Fe,  etc.  The  group  is  as  follows : 

Calcite.          Dolomite.          Magnesite.          Rhodochrosite.         Siderite.         Smithsonite. 

CaCOg      ^ao,  1  2C03     MgC03  MnCO3  FeCO3  ZnCO3 

105°  5'       10%°  15'         107°  29'  106°  51'          107°  0'  107°  40'. 

Ankerite  (parankerite),  breunerite,  mesitite,  and  pistomesite  belong  to 
the  same  group.  All  the  above  species  have  an  analogous  composition,  and 
all  crystallize  in  the  rhombohedral  system,  the  angle  of  the  fundamental 
form  varying  somewhat  in  the  different  cases. 

Mitscherlich,  who,  by  a  series  of  experimental  researches,  established  the 
principle  of  isomorphism,  expressed  it  as  follows  :  Suhatcmces,  which  are 
analogous  chemical  compounds,  have  the  same  crystalline  form,  or  are 

ISOMOEPHOUS. 

Some  of  the  more  important  isomorphous  groups  are  mentioned  below, 
for  the  description  of  the  different  species  reference  must  be  made  to 
Part  III. 

Isometric  system. — (1)  The  SPINEL  group,  having  the  general  formula 
KFK)4,  including  spinel  MgAlO4,  magnetite  FeFeO4,  chromite  FeOrO4.  also 
franklinite,  gahnite,  etc.  (2)  The  ALUM  group,  for  example,  potash-alum 
K2A1S4O16  +  24aq,  etc.  (3)  The  GAENET  group,  having  the  general  formula 
R3-RSi3012. 

Tetragonal  system. — RUTILE  group,  RO2 ;  including  rutile  TiO2,  and  cas- 
siterite  SnO2.  The  SCHEELITE  group  ;  including  scheelite  CaWO4,  stolzite 
PbWO4,  wulfenite  PbMO4. 

Hexagonal  system. — APATITE  group  ;  apatite  3Ca3P2O8  +  Ca(Cl,  F)2,  pyro- 
anorphite  3Pb3P2O8  +  PbCl2,  inimetite  3Pb3As2O8-|-PbCl2,  and  vanadinite 
^Pb3Y2O8-hPbCl2.  COEUNDUM  group,  :RO3;  corundum  A1O3,  hematite 
:FeO3.  menaccanite. 

Rhombohedral  system. — CALCITE  group,  RCO3,  already  mentioned. 

Orthorhombic  system. — AEAGONITE  group,  RCO3 ;  aragonite  CaCO3, 
witherite  BaCO3,  strontianite  SrCO3,  cerussite  PbCO3.  BAEITE  group,  RSO4 ; 
barite  BaSO4,  celestite  SrSO4,  anhydrite  CaSO4,  anglesite  PbSO4.  CHEYSO- 
LITE  group,  general  formula,  R2SiO4. 


DIMORPHISM — ISOMORPHISM.  179 

Mono  clinic  system. — COPPERAS  group ;  melanteriteFeSO4+7aq ;  bieberite 
CoSO4-j-7aq,  etc.  Pyroxene  group,  RSiO3,  etc. 

Monoclinic  and  Triclinic.     Feldspar  group. 

The  above  enumeration  includes  only  the  more  prominent  among  the 
isomorphous  groups.  In  many  other  cases  a  close  relationship  exists  among 
species,  both  in  form  and  composition,  as  brought  out  in  Dana's  System  of 
Mineralogy  (1854),  and  as  also  to  some  extent  exhibited  in  the  grouping  of 
the  species  in  the  descriptive  part  of  this  work. 

(1)  It  will  be  observed  in  the  above  that  a  replacement  of  an  element  in  a 
compound  by  one  or  more  other  elements,  chemically  equivalent,  may  take 
place  without  any  essential  change  of  the  crystalline  form.  Besides  this  a 
part  of  one  element  may  be  similarly  replaced.  This  is  illustrated  in  the 
case  of  the  rhombohedral  carbonates :  calcite  has  the  composition  CaCO3,- 
and  raagnesite  MgCO3 ;  but  in  dolomite  the  place  of  the  basic  element  is 
taken  by  Ca  and  Mg  in  equal  proportions,  so  that  the  formula  may  be 
written  (JCa  +  £Mg)CO3,  or  more  properly  CaMgC2O6.  But  besides  this 
compound  there  are  others  where  the  ratio  of  Ca  to  Mg  is  3  :  2,  also  2  :  1, 
and  3:1,  etc.  Further  than  this  the  Ca  or  Mg  may  be  in  part  replaced  by 
Mn,  Fe,  orZn. 

The  mineral  ankerite  is  one  in  which  Ca,  Mg,  Fe  (Mn),  all  enter,  and  in 
different  proportions.  Boricky  has  shown  that  the  composition  of  the 
ankerite  group  of  compounds  is  expressed  by  the  formula  : — CaCO3  +  FeCO3 
+  o<CaMgC2O6),  where  x  may  be  £,  1,  |,  f,  f,  2,  3,  4,  5,  10.  This  and  all 
similar  cases  are  examples  of  isomorphous  replacement. 

It  is  not  essential  that  the  replacing  elements  in  an  isomorphous  series 
should  have  the  same  quanti valence,  although  this  is  generally  true.  For 
example,  spodumene  is  isomorphous  with  the  pyroxene  group,  though  in  it 

the  bivalent  element  is  replaced  bv  a  sexivalent  (3R  =  fi).     So,  too,  menac- 

niv 

canite  was  included  in  the  corundum  group,  since  here  RRO3  is  isomor- 
phous with  KO3.  This  relation  of  the  elements,  which  are  not  equivalent, 
is  brought  out  by  the  method  of  viewing  the  oxides  presented  on  p.  174. 

(2).  Minerals  which  crystallize  in  different  systems  may  yet  be  isomor- 
phous, when  the  difference  between  their  geometrical  form  is  slight ;  this 
is  conspicuously  true  of  the  members  of  the  feldspar  family. 

(3).  Minerals  may  be  closely  related  in  form,  although  there  is  no  ana- 
logy whatever  between  their  chemical  composition  ;  many  such  cases  have 
been  noted,  e.g.,  axinite  and  glauberite,  azurite  and  epidote. 

Two  substances  may  be  both  homoeomorphous  and  correspondingly 
dimorphous  ;  and  they  are  then  described  as  isodimorphous.  Titanic  oxide 
(TiO2),  and  stannic  oxide  (SnO8),  are  both  dimorphous,  and  they  are  also 
homoeomorphous  severally  in  each  of  the  two  forms.  This  is  an  example 
of  isodimorphism. 

There  are  also  cases  of  isotrimorphism.  Thus  there  are  the  following 
related  groups  ;  the  angle  of  the  rhombohedral  forms  here  given  is  R  :  jR  ; 
of  the  orthorhombic  and  rnonoclinic  /  :  /(for  baryto-calcite  2-&  on  2-fc): 

Rhombohedral.  Orthorhombic.  Monoclinic. 

RCO3  Calcite,  105°  5'.  Aragonite,  116°  10'.  Barytocalcite,  95°  8'. 

KSO4  Dreelite,  93°-94°.  Anglesite,  103°  38'.  Glauberite,  83°-83°  20'. 

RS04+nRC03        Susannite,  94°.  Leadhillite,  103°  16'.  Lanarkite,  84°. 


180  CHEMICAL   MINERALOGY. 

Calcite,  aragonite,  and  barytocalcite  form  an  undoubted  case  of  trimor- 
phism,  as  has  already  been  shown.  Dreelite,  anglesite,  and  glauberite 
constitute  another  like  series,  and  moreover  it  is  closely  parallel  in  angle 
with  the  former.  In  the  third  line  we  have  the  sulphato-carbonate  susan- 
iiite  near  dreelite  in  angle,  leadhillite  (identical  with  susatmite  in  composi- 
tion) near  anglesite,  and  lanarkite,  another  sulphato-carbonate,  near  glau- 
berite, forming  thus  a  third  parallel  line.  The  sulphuric  acid  in  these  sul- 
phato-carbonates  dominates  over  the  carbonic  acid,  and  gives  the  form  of 
the  sulphates  enumerated  in  the  second  line  of  the  table. 

CHEMICAL  EXAMINATION  OF  MINERALS. 

The  chemical  characters  of  minerals  are  ascertained  (a)  by  the  action  of 
acids  and  other  reagents ;  (b)  by  means  of  the  blowpipe  assisted  by  a  few 
chemical  reagents  ;  (c)  by  chemical  analysis.  The  last  method  is  the  only 
one  by  which  the  exact  chemical  composition  of  a  mineral  can  be  deter- 
mined. It  belongs,  however,  wholly  to  chemistry,  and  it  is  unnecessary  to 
touch  upon  it  here  except  to  call  attention  to  the  remarks  already  made 
(p.  156)  upon  the  essential  importance  of  the  use  of  pure  material  for  analysis. 

The  various  tests  and  reactions  of  the  wet  and  dry  methods  are  important, 
since  they  often  make  it  possible  to  determine  a  mineral  with  very  little 
labor,  and  this  with  the  use  of  the  minimum  amount  of  material. 

a.  Examination  in  the  Wet  Way. 

The  most  common  chemical  reagents  are  the  three  mineral  acids,  hydro- 
chloric, nitric,  and  sulphuric.  In  testing  the  powdered  mineral  with  these 
acids,  the  important  points  to  be  noted  are :  (1)  the  degree  of  solubility, 
and  (2)  the  phenomena  attending  entire  or  partial  solution  ;  that  is,  whether 
a  gas  is  evolved,  producing  effervescence,  or  a  solution  is  obtained  without 
effervescence,  or  an  insoluble  constituent 'is  separated  out. 

Solubility. — In  testing  the  degree  of  solubility  hydrochloric  acid  is  most 
commonly  used,  though  in  the  case  of  sulphides,  and  compounds  of  lead 
and  silver,  nitric  acid  is  required.  Less  often  sulphuric  acid,  and  aqua 
regia  (nitro-hydrochloric  acid),  are  resorted  to. 

Many  minerals  are  completely  soluble  without  effervescence  :  among  these 
are  some  of  the  oxides,  hematite,  limonite,  gothite,  etc.,  some  sulphates, 
many  phosphates  and  arseniates,  etc. 

Solubility  with  effervescence  takes  place  when  the  mineral  loses  a  gaseous 
ingredient,  or  when  one  is  generated  by  the  mutual  decomposition  of  acid 
and  mineral.  Most  conspicuous  here  are  the  carbonates,  all  of  which  dissolve 
with  effervescence,  giving  off  carbonic  acid  (properly  carbon  dioxide,  CO2), 
though  some  of  them  only  when  pulverized,  or  again,  on  the  addition  of 
heat.  In  applying  this  test  dilate  hydrochloric  acid  is  employed.  Sul- 
phuretted hydrogen  (H2S)  is  evolved  by  some  sulphides,  when  dissolved  in 
hydrochloric  acid:  this  is  true  of  sphalerite,  stibnite,  greenockite,  etc. 
Chlorine  is  evolved  by  oxides  of  manganese  and  also  chromic  and  vanadic 
acid  salts,  when  dissolved  in  hydrochloric  acid.  Nitric  peroxide  is  given 
off  by  many  metallic  minerals,  and  also  some  of  the  lower  oxides  (cuprite, 
etc.),  when  treated  with  nitric  acid. 


CHEMICAL    EXAMINATION    OF   MINERALS. 


181 


The  separation  of  an  insoluble  ingredient  takes  place  :  With  many  sili- 
cates, the  silica  separating  sometimes  as  a  fine  powder,  and  again  as  a  jelly  ; 
in  the  latter  case  the  mineral  is  said  to  gelatinize  (sodalite,  anal  cite).  In 
order  to  test  this  point  the  finely  pulverized  silicate  is  digested  with  strong 
hydrochloric  acid,  and  the  solution  afterward  slowly  evaporated  nearly  to 
dryness.  With  a  considerable  number  of  silicates  the  gelatinization  takes 
place  only  after  ignition  ;  while  others,  which  ordinarily  gelatinize,  are 
rendered  insoluble  by  ignition. 

With  many  sulphides  a  separation  of  sulphur  takes  place  when  they  are 
treated  with  nitric  acid.  Compounds  of  titanic  and  tungstic  acids  are 
decomposed  by  hydrochloric  acid  with  the  separation  of  the  oxides  named. 
The  same  is  true  of  salts  of  molybdic  and  vanadic  acids,  only  that  here  the 
oxides  are  soluble  in  an  excess  of  the  acid. 

Compounds  containing  silver,  lead,  and  mercury  give  with  hydrochloric 
acid  insoluble  residues  of  the  chlorides.  These  compounds  are,  however, 
soluble  in  nitric  acid. 

When  compounds  containing  tin  are  treated  with  nitric  acid,  the  stannic 
oxide  separates  as  a  white  powder.  A  corresponding  reaction  takes  place 
under  similar  circumstances  with  minerals  containing  arsenic  and  antimony. 

Insoluble  minerals. — A  large  number  of  minerals-  are  not  sensibly 
attacked  by  any  of  the  acids.  Among  these  may  be  named  the  following 
oxides:  corundum,  spinel,  chromite,  diaspore,  rutile,  cassiterite,  quartz; 
also  cerargyrite  ;  many  silicates,  titanates,  tantalates,  a"nd  columbates ;  also 
the  sulphates  (barite,  celestite,  anglesite) ;  many  phosphates  (xenotime, 
lazulite,  childrenite,  arnblygonite),  and  the  borate,  boracite. 


&.  Examination  of  Minerals  by  means  of  the  Blowpipe. 

Blowpipe. — The  simplest  form  of  the  blowpipe  is  a  tapering  tube  of 
brass  (f.  413,  1),  with  a  minute  aperture  at  the 
extremity.  A  chamber  is  advantageously 
added  (f.  413,  2)  at  o,  to  receive  the  condensed 
moisture,  and  an  ivory  mouth-piece  is  often 
very  convenient.  In  the  better  forms  of  the 
instrument  (see  f.  413,  3),  the  tip  is  made  of 
solid  platinum  (r/),  which  admits  of  being 
readily  cleaned  when  necessary.  Operations 
with  the  blowpipe  often  require  an  uninter- 
mitted  heat  for  a  considerable  length  of  time, 
and  always  longer  than  a  single  breath  of  the 
operator.  It  is  therefore  requisite  that  breath- 
ing and  blowing  should  go  on  together.  This 
may  be  difficult  at  first,  but  the  necessary  skill 
or  tact  is  soon  acquired. 

Blowpipe-flame. — The  best  and  most  con- 
venient source  of  heat  for  blowpipe  purposes 
is  ordinary  illuminating  gas.  The  burner  is  a 
simple  tube,  flattened  at  the  top,  and  cut  off  a 
little  obliquely  ;  it  thus  furnishes  a  flame  of  convenient  shape.  A  similar 


182  CHEMICAL   MINERALOGY. 

jet  may  also  be  used  in  conjunction  with  the  ordinary  Bunsen  burner,  it 
being  so  made  as  to  slip  down  within  the  outer  tube,  and  cut  off  the  supply 
of  air,  thus  giving  a  luminous  flame.  The  gas  flame  required  need  not  be 
more  than  an  inch  and  a  half  in  height.  In  place  of  the  gas,  a  lamp  fed 
with  olive  oil  will  answer,  or  even  a  good  candle. 

The  jet  of  the  blowpipe  is  brought  close  to  the  gas  flame  on  the  higher 
side  of  the  obliquely  terminated  burner.  The  arm  of  the  blowpipe  is 
inclined  a  little  downward,  and  the  blast  of  air  produces  an  oblique  conical 
flame  of  intense  heat.  This  blowpipe  flame  consists  of  two  cones  :  an  inner 
of  a  blue  color,  and  an  outer  cone  which  is  yellow.  The  heat  is  most 
intense  just  beyond  the  extremity  of  the  blue  flame,  and  the  mineral  is  held 
at  this  point  when  its  fusibility  is  to  be  tested. 

The  inner  flame  is  called  the  .REDUCING  FLAME  (R.F.) ;  it  is  characterized 
by  the  excess  of  the  carbon  or  hydrocarbons  of  the  gas,  which  at  the  high 
temperature  present  tend  to  combine  with  the  oxygen  of  the  mineral 
brought  into  it,  or  in  other  words,  to  reduce  it.  The  best  reducing  flame 
is  produced  when  the  blowpipe  is  held  a  little  distance  from  the  gas"  flame; 
it  should  retain  the  yellow  color  of  the  latter. 

The  outer  cone  is  called  the  OXIDIZING  FLAME  (O.F.) ;  it  is  characterized 
by  the  excess  of  the  oxygen  of  the  air  over  the  carbon  of  the  gas  to  be  com- 
bined with  it,  and  has  hence  an  oxidizing  effect  upon  the  assay.  This 
flame  is  best  produced  when  the  jet  of  the  blowpipe  is  inserted  a  very  little 
in  the  gas  flame ;  it  should  be  entirely  non-luminous. 

Supports. — Of  other  apparatus  required,  the  most  essential  articles  are 
those  which  serve  to  support  the  mineral  in  the  flame ;  these  supports  are  : 
(1)  charcoal,  (2)  platinum  forceps,  (3)  platinum  wire,  and  (4)  glass  tubes. 

(1)  Charcoal  is  especially  useful  as  a  support  in  the  case  of  the  examina- 
tion of  metallic  minerals,  where  a  reduction  is  desired.     It  must  not  crack 
when  heated,  and  should  not  yield  any  considerable  amount  of  ash  on  com- 
bustion ;  that  made  from  soft  wood  (pine  or  willow)  is  the  best.     Pieces  of 
convenient  size  for  holding  in  the  hand  are  employed  ;  they  should  have  a 
smooth  surface,  and  a  small  cavity  should  be  in  it  made  for  the  mineral. 

(2)  A  convenient  kind  of  platinum  forceps  is  represented  in  f.  414  ;  it 
is  made  of  steel  with  platinum  points.     These  open  by  means  of  the  pins 


414 


pp  ;  other  forms  open  by  the  spring  of  the  wire  in  the  handle.  Care  must 
be  taken  not  to  heat  any  substance  (e.g.,  metallic)  in  the  forceps,  which  when 
fused  might  injure  the  platinum. 

(3)  Platinum  wire  is  employed  with  the  use  of  fluxes,  as  described  in 
another  place. 

(4)  The  glass  tubes  required  are  of  two  kinds  :  closed  tubes,  having  only 
one  open  end,  about  four  inches  long ;  and  open  tubes,  having  both  ends 
open,  four  to  six  inches  in  length.     Both  kinds  can  be  easily  made  by  the 
student  from  ordinary  tubing  (best  of  rather  hard  glass),  having  a  bore  of 

to     of  an  inch. 


CHEMICAL   EXAMINATION   OF   MINERALS.  183 

In  the  way  of  additional  apparatus,  the  following  articles  are  useful ;  they 
need  no  special  description  :  hammer,  small  anvil,  three-cornered  file,  mag- 
net, pliers,  pocket-lens,  and  a  small  mortar,  as  also  a  few  of  the  test-tubes, 
etc.,  used  in  the  laboratory. 

Chemical  reagents. — The  commonest  reagents  employed  are  the  fluxes, 
viz.,  soda  (sodium  carbonate)  ;  salt  of  phosphorus  (sodium-ammonium 
phosphate) ;  and  borax  (sodium  biborate).  The  method  of  using  them  is 
spoken  of  on  p.  186. 

Nitrate  of  cobalt  in  solution  is  also  employed.  It  is  conveniently  kept 
in  a  small  bulb  from  which  a  drop  or  two  may  be  obtained  as  it  is  needed. 
This  is  used  principally  as  a  test  for  aluminum  or  magnesium  with  infusible 
minerals,  as  remarked  beyond.  The  fragment  of  the  mineral  held  in  the 
forceps  is  first  ignited  in  the  blowpipe  name,  a  drop  of  the  cobalt  solution 
is  placed  on  it,  and  then  it  is  heated  again  ;  the  presence  of  either  constitu- 
ent named  is  manifested  by  the  color  assumed  by  the  ignited  mineral.  It 
is  also  used  as  a  test  for  zinc.  Potassium  bisulphate  and  calcium  fluoride 
(fluorite)  in  powder,  metallic  magnesium  (foil  or  wire),  and  tin  foil,  are 
other  reagents,  the  use  of  which  is  explained  later.  Test-papers  are  also 
needed,  viz.,  blue  litmus  paper,  and  turmeric  paper. 

The  wet  reagents  required  are :  the  ordinary  acids,  and  most  important 
of  these  hydrochloric  acid,,  generally  diluted  one-half  for  use,  and  also 
barium  chloride,  silver  nitrate,  ammonium  molybdate. 

The  blowpipe  investigation  of  minerals  includes  their  examination,  (1)  in 
the  platinum-pointed  forceps,  (2)  in  the  closed  tube,  (3)  in  the  open  tube, 
(4)  on  charcoal,  and  (5)  with  the  fluxes. 

(1)  Elimination  in  the  forceps. — The  most  important  use  of  the  plati- 
num-pointed forceps  is  to  hol^l  the  fragment  of  the  mineral  while  its  fusi- 
bility is  tested. 

The  following-  practical  points  must  be  regarded  :  (1)  Metallic  minerals,  which  when  fused 
may  injure  the  platinum,  should  be  examined  on  charcoal ;  (2)  the  fragment  taken  should  be 
thin,  and  as  small  as  can  conveniently  be  held;  (3)  when  decrepitation  takes  place,  the  heat 
must  be  applied  slowly,  or,  if  this  does  not  prevent  it,  the  mineral  may  be  powdered  and  a 
paste  made  with  water,  thick  enough  to  be  held  in  the  forceps  or  on  the  platinum  wire  ;  or 
the  paste  may,  with  the  same  end  in  view,  be  heated  on  charcoal ;  (4)  the  fragment  whose 
fusibility  is  to  be  tested  must  be  held  in  the  hottest  part  of  the  flame,  just  beyond  the 
extremity  of  the  blue  cone. 

Iii  connection  with  the  trial  of  fusibility,  the  following  phenomena  may 
be  observed  :  (a)  a  coloration  of  the  flame ;  (b)  a  swelling  up  (stilbite),  or 
an  exfoliation  of  the  mineral  (vermiculite) ;  or  (c)  a  glowing  without  fusion 
(calcite) ;  and  (d)  an  intumescence,  or  a  spirting  out  of  the  mass  as  it  fuses 
(scapolite),  The  color  of  the  mineral  after  ignition  is  to  be  noted  ;  and  the 
nature  of  the  fused  mass  is  also  to  be  observed,  whether  a  clear  or  blebby 
glass  is  obtained,  or  a  black  slag,  or  whether  magnetic  or  not,  etc. 

The  ignited  fragment,  if  nearly  or  quite  infusible,  may  be  moistened 
with  the  cobalt  solution  and  again  ignited  (see  above) ;  also,  if  not  too 
fusible,  it  may,  after  treatment  in  the  forceps,  be  placed  upon  a  strip  of 
moistened  turmeric  paper,  in  which  case  an  alkaline  reaction  shows  the 
presence  of  the  alkaline  earths. 

Fusibility. — All  grades  of  fusibility  exist  among  minerals,  from  those 


184  CHEMICAL   MINERALOGY. 

which  fuse  in  large  fragments  in  the  flame  of  the  candle  (stibnite,  see 
below),  to  those  which  fuse  only  on  the  thinnest  edges  in  the  hottest  blow- 
pipe flame  (bronzite) ;  and  still  again  there  are  a  considerable  number 
which  are  entirely  infusible  (e.g.,  corundum). 

The  following  scale  of  fusibility,  proposed  by  von  Kobell,  is  made  use 
of:  1,  stibnite  ;  2,  natrolite  ;  3,  almandiiie  garnet ;  4,  actinolite  ;  5,  ortho- 
clase  ;  6,  bronzite. 

A  little  practice  with  these  minerals  will  show  the  student  what  degree 
of  fusibility  is  expressed  by  each  number,  and  render  him  quite  independent 
of  the  table;  he  will  thus  be  able  also  to  judge  of  his  power  to  produce  a 
hot  flame  by  the  blowpipe,  which  requires  practice. 

Flame  coloration. — When  coloration  is  produced  it  is  seeji  on  the  exterior 
portion  of  the  flame,  and  is  best  observed  when  shielded  from  the  direct  light. 

The  presence  of  soda,  even  in  small  quantities,  produces  a  yellow  flame,  which  (except  in 
the  spectroscope)  more  or  less  completely  masks  the  coloration  of  the  flame  due  to  other  sub- 
stances ;  phosphates  and  borates  give  the  green  flame  in  general  best  when  they  have  been 
pulverized  and  moistened  with  sulphuric  acid ;  moistening  with  hydrochloric  acid  makes  the 
coloration  in  many  cases  (barium,  strontium)  more  distinct. 

The  colors  which  may  be  produced,  and  the  substances  to  whose  presence 
they  are  due,  are  as  follows:  (1)  yellow,  sodium ;  (2)  violet,  potassium  ; 

(3)  purple-red,  lithium ;  red,  strontium ;   yellowish-red,  calcium  (lime) ; 

(4)  yellowish-green,  barium,  molybdenum  ;  emerald-green,  copper;  bluish- 
green,  phosphorus  (phosphates) ;  yellowish-green,  boron  (borates) ;  (5)  blue, 
azure-blue,  copper  chloride  ;  light-blue,  arsenic  ;  greenish-blue,  antimony. 

(2)  Heating  in  the  closed  tube. — The  closed  tube  is  employed  to  show 
the  effect  of  heating  the  mineral  out  of  contact  with  the  air.     A  small  frag- 
ment is  taken,  or  sometimes  the  powdered  mineral  is  inserted,  though  in 
this  case  with  care  not  to  soil  the  sides  of  the  tube.     The  phenomena  which 
may  be  observed  are  as  follows  :  decrepitation,  as  shown  by  fluorite,  calcite, 
etc. ;  glowing,  as  exhibited  by  gadolinite  ;  phosphorescence,  of  which  fluorite 
is  an  example  ;  change  of  color  (limonite),  and  here  the  color  of  the  mineral' 
should  be  noted  both  when  hot,  and  again  after  cooling;  fusion  ;  giving  off 
oxygen,  as  mercuric  oxide ;  yielding  water  at  a  low  or  high  temperature, 
which  is  true  of  all  hydrous  minerals ;  yielding  acid  or  alkaline  vapors, 
which  should  be  tested  by  inserting  a  strip  of  moistened  litmus  or  turmeric 
paper  in  the  tube ;  yielding  a  sublimate,  which  condenses  in  the  cold  part 
of  the  tube. 

Of  the  sublimates  which  form  in  the  tube,  the  following  are  those  w^ith 
which  it  is  most  important  to  be  familiar:  Sublimate  yellow,  sulphur; 
dark  brown- red  when  hot,  and  red  or  reddish-yellow  when  cold,  arsenic 
sulphide;  brilliant  black,  arsenic  (also  giving  off  a  garlic  odor);  black 
when  hot,  brown-red  when  cold,  formed  near  the  mineral  by  strong  heating, 
antimony  oxysulphide  ;  dark-red,  selenium  (also  giving  the  odor  of  decay- 
ing horseradish) ;  sublimate  consisting  of  small  drops  with  metallic  lustre, 
tellurium  ;  sublimate  gray,  made  up  of  minute  metallic  globules,  mercury  ; 
sublimate  black,  lustreless,  red  when  rubbed,  mercury  sulphide. 

(3)  Heating  in  the  open  tube. — The  small  fragment  is  placed  in  the  tube 
about  an  inch  from  the  lower  end,  the  tube  being  inclined  sufficiently  to 
prevent  the  mineral  from  slipping  out.     The  current  of  air,  passing  through 


CHEMICAL   EXAMINATION    OF   MINERALS.  185 

the  tube  during  the  heating  process,  has  an  oxidizing  effect.  The  special 
phenomena  to  be  observed  are  the  formation  of  a  sublimate  and  the  odor 
of  the  escaping  gases.  The  acid  or  alkaline  character  of  the  vapors  are 
tested  in  the  same  way  as  with  the  closed  tube.  Fluorides,  when  heated  in 
the  open  tube  with  previously  fused  salt  of  phosphorus,  yield  hydrofluoric 
acid,  which  gives  an  acid  reaction  with  test-paper,  has  a  peculiar  pungent 
odor,  and  corrodes  the  glass. 

The  sublimates  which  may  be  formed,  as  far  as  they  differ  from  those 
already  mentioned,  as  obtained  in  the  closed  tube,  are  as  follows :  Subli- 
mate, white  and  crystalline,  volatile,  arsenous  oxide  •  white,  near  the  min- 
eral crystalline,  fusible  to  minute  drops,  yellowish  when  hot,  nearly  color- 
less when  cold,  molybdic  oxide ;  sublimate  white,  yielding  dense  white 
fumes,  at  first  mostly  volatile,  forming  on  the  upper  side  of  the  tube,  and 
afterward  generally  non-volatile  on  the  under  side  of  the  tube,  antimonous 
and  antimonic  oxides  /  sublimate  dark  brown  when  hot,  lemon-yellow 
when  cold,  fusible,  bismuth  oxide;  sublimate  gray,  fusible  to  colorless 
drops,  tellurous  oxide  /  sublimate  steel-gray,  the  upper  edge  appearing  red, 
selenium  ;  sublimate  bright  metallic,  mercury. 

The  odors  which  may  be  perceived  are  the  same  as  those  mentioned  in 
the  following  article. 

(4)  Heating  alone  on  charcoal. — The  substance  to  be  examined  is  placed 
in  a  shallow  cavity  ;  it  may  simply  be  a  small  fragment,  or,  where  the 
mineral  decrepitates,  it  may  be  powdered,  mixed  with  water,  and  thus  the 
material  employed  as  a  paste.  The  points  to  be  noticed  are : 

(a)  The  odor  given  off  after  short  heating.     In  this  way  the  presence  of 
sulphur,  arsenic  (garlic  odor),  and  selenium  (odor  of  decayed  horseradish), 
may  be  recognized. 

(b)  Fusion. — In  the  case  of  the  salts  of  the  alkalies  the  fused  mass  is 
absorbed  into  the  charcoal ;  this  is  also  true,  after  long  heating,  of  the  car- 
bonates and  sulphates  of  barium  and  strontium. 

(c)  The  infusible  residue. — This  may  (1)  glow  brightly  in  the  O.F.,  indi- 
cating the  presence  of  calcium,  strontium,  magnesium,  zirconium,  zinc,  or 
tin.     (2)  It  may  give  an  alkaline  reaction  after  ignition  :  alkaline  earths. 
(3)  It  may  be  magnetic,  showing  the  presence  of  iron. 

(d)  The  sublimate. — By  this  means  the  presence  of  many  of  the  metals 
may  be  determined.     The  color  of  the  sublimate,  both  near  the  assay  (N), 
and  at  a  distance  (D) ;  as  also  when  hot  and  when  cold  is  to  be  noted. 

The  most  important  of  the  sublimates,  with  the  metals  to  which  they  are 
due,  are  contained  in  the  following  list:  Sublimate,  steel-gray  (N),  and 
dark  gray  (D),  in  R.F.  volatile  with  a  blue  flame,  selenium  (also  giving  a 
peculiar  odor) ;  white  (N)  and  red  or  deep  yellow  (D),  in  R.F.  volatile  with 
green  flame,  tellurium  ;  white  (N)  and  grayish  (D),  arsenic  (giving  also  a 
peculiar  alliaceous  odor) ;  white  (N)  and  bluish  (D),  antimony  (also  giving 
off  dense  white  fumes).  Reddish-brown,  silver  /  dark  orange-yellow  when 
hot,  and  lemon-yellow  when  cold  (N),  also  bluish-white  (D),  bismuth  /  dark 
lemon-yellow  when  hot,  sulphur-yellow  when  cold,  lead ;  red-brown  (N) 
and  orange-yellow  (D),  cadmium  ;  yellow  when  hot,  white  on  cooling,  zinc 
(the  sublimate  becomes  green  if  moistened  with  cobalt  solution  and  again 
ignited) ;  faint  yellow  when  hot,  white  on  cooling,  tin  (the  sublimate 
becomes  bluish-green  when  ignited  after  being  moistened  with  the  cobalt 


186  CHEMICAL   MINEEALOGY. 

solution,  in  the  R.F.  it  is  reduced  to  metallic  tin) ;  yellow,  sometimes  crys- 
talline when  hot,  white  when  cold  (N),  bluish  (D),  molybdenum  (in  O.F. 
the  sublimate  volatilizes,  leaving  a  permanent  stain  of  the  oxide,  in  R.F. 
gives  an  azure  blue  color  when  touched  for  a  moment  with  the  flame). 

(5)  Treatment  with  the  fluxes. — The  three  fluxes  have  been  mentioned 
on  p.  183.  They  are  used  either  on  charcoal  or  with  the  platinum  wire. 
If  the  latter  is  employed  it  must  have  a  small  loop  at  the  end  ;  this  is  heated 
to  redness  and  dipped  into  the  powdered  flux,  and  the  adhering  particles 
fused  to  a  bead  ;  this  operation  is  repeated  until  the  loop  is  filled.  Some- 
times in  the  use  of  soda  the  wire  may  at  first  be  moistened  a  little  to  cause 
it  to  adhere.  When  the  bead  is  ready  it  is,  while  hot,  brought  in  contact 
with  the  powdered  mineral,  some  of  which  will  adhere  to  it,  and  then  the 
heating  process  may  be  continued.  Very  little  of  the  mineral  is  in  general 
required,  and  the  experiment  should  be  commenced  with  a  minute  quantity 
and  more  added  if  necessary.  The  bead  must  be  heated  successively  in 
the  reducing  and  oxidizing  flames,  and  in  each  case  the  color  noted  when 
hot  and  when  cold.  The  phenomena  connected  with  fusion,  if  it  takes 
place,  must  also  be  observed. 

Minerals  containing  sulphur  or  arsenic,  or  both,  must  be  first  roasted,  that  is,  heated  on 
charcoal,  first  in  the  oxidizing  and  then  in  the  reducing  flame,  till  these  substances  have  been 
volatilized.  If  too  much  of  the  mineral  has  been  added  and  the  bead  is  hence  too  opaque  to 
show  the  color,  it  may,  while  hot,  be  flattened  out  with  the  hammer,  or  drawn  out  into  a 
wire,  or  part  of  it  may  be  removed  and  the  remainder  diluted  with  more  of  the  flux. 

BORAX. — The  following  list  enumerates  the  different  colored  beads 
obtained  with  borax,  and  also  the  metals  to  the  presence  of  whose  oxides 
the  colors  are  due  : 

Colorless ;  silica,  aluminum,  the  alkaline  earths,  etc.  (both  O.F.  and 
R.F.) ;  also  silver,  zinc,  cadmium,  lead,  bismuth,  and  nickel,  O.F.,  and  also 
R.F.,  after  long  heating,  but  when  first  heated,  gray  or  turbid ;  R.F.,  man- 
ganese. 

Yellow  /  in  O.F.,  titanium,  tungsten,  and  molybdenum,  also  zinc  and 
cadmium,  when  strongly  saturated  and  hot y  vanadium  (greenish  when 
hot) ;  iron,  uranium,  and  chromium,  when  feebly  saturated. 

Red  to  brown  •  in  O.F.,  iron,  hot  (on  cooling,  yellow) ;  O.F.,  chromium, 
hot  (yellowish-green  when  cold) ;  O.F.,  uranium,  hot  (yellow  when  cold) ; 
nickel,  manganese,  cold  (violet  when  hot). 

Red ;  R.F.,  copper,  if  highly  saturated,  cold  (colorless  when  hot). 

Violet ;  O.F.,  nickel,  hot  (red-brown  to  brown  on  cooling) ;  O.F.,  man- 
ganese. 

Blue;  O.F.  and  R.F.,  cobalt,  both  hot  and  cold;  O.F.,  copper,  cold 
(when  hot,  green). 

Green  •  O.F.,  copper,  hot  (blue  or  greenish-blue  on  cooling),  R.F.,  bottle- 
green  ;  O.F.,  chromium,  cold  (yellow  to  red  when  hot),  R.F.,  emerald-green ; 
O.F.,  vanadium,  cold  (yellow  when  hot),  R.F.,  chrome-green,  cold  (brown- 
ish when  hot) ;  R.F.,  uranium,  yellowish-green  (when  highly  saturated). 

SALT  OF  PHOSPHORUS. — This  flux  gives  for  the  most  part  reactions  similar 
to  those  obtained  with  borax.  The  only  cases  enumerated  here  are  those 
which  are  distinct,  and  hence  those  where  the  flux  is  a  good  test. 

With  silicates  this  flux  forms  a  glass  in  which  the  bases  of  the  silicate 


CHEMICAL   EXAMINATION    OF    MINERALS.  187 

are  dissolved,  but  the  silica  itself  is  left  insoluble.  It  appears  as  a  skeleton 
readily  seen  floating  about  in  the  melted  bead. 

The  colors  of  the  beads  and  the  metals  to  whose  oxides  these  are  due,  are : 

J3lue  •  R.F.j  tungsten,  cold  (brownish  when  hot) ;  R.F.,  coluinbium,  cold 
and  when  highly  saturated  (dirty-blue  when  hot).  Both  these  give  colorless 
beads  in  the  O.F. 

Green ;  R.F.,  uranium,  cold  (yellowish-green  when  hot) ;  O.F.,  molyb- 
denum, pale,  on  cooling,  also  R.F.,  dirty-green  when  hot,  green  when  cold. 

Violet  /  R.F.,  columbium  (see  above) ;  R.F.,  titanium  cold  (yellow  when 
hot). 

SODA  is  especially  valuable  as  a  flux  in  the  case  of  the  reduction  of  the 
metallic  oxides  ;  this  is  usually  performed  on  charcoal.  The  finely  pulver- 
ized mineral  is  intimately  mixed  with  soda,  and  a  drop  of  water  added  to 
form  a  paste.  This  is  placed  in  a  cavity  in  the  charcoal,  and  subjected  to 
a  strong  reducing  flame.  More  soda  is  added  as  that  present  sinks  into  the 
coal,  and,  after  the  process  has  been  continued  some  time,  the  remainder 
of  the  flux,  the  assay,  and  the  surrounding  coal  are  cut  out  with  a  knife, 
and  the  whole  ground  up  in  a  mortar,  with  the  addition  of  a  little  water. 
The  charcoal  is  carefully  washed  away  and  the  metallic  globules,  flattened 
out  by  the  process,  remain  behind.  Some  metallic  oxides  are  very  readily 
reduced,  as  lead,  while  others,  as  copper  and  tin,  require  considerable  skill 
arid  care. 

The  metals  obtained  may  be:  iron,  nickel,  or  cobalt,  recognized  by  their 
being  attracted  by  the  magnet;  or  copper,  marked  by  its Ved  color ;  bis- 
muth and  antimony,  which  are  brittle  ;  gold  or  silver ;  antimony,  tellurium, 
bismuth,  lead,  zinc,  cadmium,  which  volatilize  more  or  less  completely  and 
may  be  recognized  by  their  sublimates  (see  p.  185) ;  arsenic  and  mercury 
are  also  reduced,  but  must  be  heated  with  soda  in  the  closed  tube  in  order 
to  collect  the  sublimates.  The  metals  obtained  may  be  also  tested  with 
borax  on  the  platinum  wire. 

By  means  of  soda  on  charcoal  the  presence  of  sulphur  in  the  sulphates 
may  be  shown,  though  they  do  not  yield  it  upon  simple  heating.  When 
soda  is  fused  on  charcoal  with  a  compound  of  sulphur  (sulphide  or  sulphate), 
sodium  sulphide  is  formed,  and  if  much  sulphur  is  present  the  mass  will 
have  the  hepar  (liver-brown)  color.  In  any  case  the  presence  of  the  sulphur 
is  shown  by  placing  the  fused  mass  on  a  clean  surface  of  silver,  and  adding 
a  drop  of  water ;  a  black  or  yellow  stain  of  silver  sulphide  will  be  formed. 
Illuminating  gas  often  contains  sulphur,  and  hence,  when  it  is  used,  the 
soda  should  be  first  tried  alone  on  charcoal,  and  if  a  sulphur  reaction  is 
obtained  (due  to  the  gas),  a  candle  or  lamp  must  be  employed  in  the  place 
of  the  gas. 

It  is  also  useful  in  the  case  of  many  minerals  to  test  their  fusibility  or 
inf usibility  with  soda,  generally  on  the  platinum  wire.  Silica  forms  if  not 
in  excess  a  clear  glass  with  soda,  so  also  titanic  acid.  Salts  of  barium  and 
strontium  are  fusible  with  soda,  but  the  mass  is  absorbed  by  the  coal. 
Many  silicates,  though  alone  difficultly  fusible,  dissolve  in  a  little  soda  to  a 
clear  glass,  but  with  more  soda  they  form  an  infusible  mass.  Manganese, 
when  present  even  in  minute  quantities,  gives  a  bluish-green  color  to  the 
soda  bead. 


188  CHEMICAL    MINERALOGY. 


CHARACTERISTIC  REACTIONS  OF  THE  MOST  IMPORTANT  ELEMENTS  AND  OP  SOME  OP 

THEIR  COMPOUNDS. 

The  following  list  contains  the  most  characteristic  reactions,  both  before 
the  blowpipe  (B.B.)  and  in  some  cases  in  the  wet  way,  of  the  different  ele- 
ments and  their  oxides.  It  is  desirable  for  every  student  to  be  familiar 
with  them.  Many  of  them  have  already  been  briefly  mentioned  in  the 
preceding  pages.  It  is  to  be  remembered  that  while  the  reaction  of  a 
single  substance  may  be  perfectly  distinct  if  alone,  the  presence  of  other 
substances  may  more  or  less  entirely  obscure  these  reactions  ;  it  is  conse- 
quently obvious  that  in  the  actual  examination  of  minerals  precautions  have 
to  be  taken,  and  special  methods  have  to  be  devised,  to  overcome  the  diffi- 
culty arising  from  this  cause.  These  will  be  gathered  from  the  pyrognostic 
characters  given  (by  Prof.  Brush)  in  connection  with  the  description  of 
each  species  in  the  Third  Part  of  this  work. 

For  many  substances  the  most  satisfactory  and  delicate  tests  are  those 
which  have  been  given  by  Bunsen  in  his  important  paper  on  Flame-reac- 
tions (Flainmenreaetionen,  Ann.  Ch.  Pharm.,  cxxxviii.,  257,  or  Phil.  Mag., 
IY.,  xxxii.,  81).  The  methods,  however,  require  for  the  most  part  much 
detailed  explanation,  and  in  this  place  it  is  only  possible  to  make  this  gen- 
eral reference  to  the  subject. 

Alumina.  B.B. ;  the  presence  of  alumina  in  most  infusible  minerals, 
containing  a  considerable  amount,  may  be  detected  by  the  blue  color  which 
they  assume  when,  after  being  heated,  they  are  moistened  with  cobalt  solu- 
tion and  again  ignited.  Yery  hard  minerals  (e.g.,  corundum)  must  be  first 
finely  pulverized. 

Antimony.  B.B. ;  antirnonial  minerals  on  charcoal  give  dense  white 
inodorous  fumes.  Antimony  sulphide  gives  in  a  strong  heat  in  the  closed 
tube  a  sublimate,  black  when  hot,  brown-red  when  cold.  See  aleo  p.  185. 

In  nitric  acid  compounds  containing  antimony  deposit  white  antimonic 
oxide  (Sb2O5). 

Arsenic.  B.B.  ;  arsenical  minerals  give  off  fumes,  usually  easily  recog- 
nized by  their  peculiar  garlic  odor.  In  the  open  tube  they  give  a  white, 
volatile,  crystalline  sublimate  of  arsenious  oxide.  In  the  closed  tube  arsenic 
sulphide  gives  a  sublimate  dark  brown-red  when  hot,  and  red  or  reddish- 
yellow  when  cold.  The  presence  of  arsenic  in  minerals  is  often  proved  by 
testing  them  in  the  closed  tube  with  sodium  carbonate  and  potassium  cyan- 
ide. Strong  heating  produces  a  sublimate  of  metallic  arsenic,  proper  pre- 
cautions being  observed. 

Baryta.  B.B. ;  a  yellowish-green  coloration  of  the  flame  is  given  by  all 
baryta  salts,  except  the  silicates. 

In  solution  the  presence  of  barium  is  proved  by  the  heavy  white  precipi  - 
tate  formed  upon  the  addition  of  dilute  sulphuric  acid. 

Bismuth.  B.B.  ;  on  charcoal  alone,  or  with  soda,  bismuth  gives  a  very 
characteristic  orange-yellow  sublimate  (p.  185).  Also  when  treated  with 
equal  parts  of  potassium  iodide  and  sulphur,  and  fused  on  charcoal,  a  beauti- 
ful red  sublimate  of  bismuth  iodide  is  obtained. 

Boraoic  acid.  Borates.  B.B. ;  many  compounds  tinge  the  flame  intense 
yellowish-green,  especially  if  moistened  with  sulphuric  acid.  For  silicates 


CHARACTERISTIC    REACTIONS    OF   THE    DIFFERENT    ELEMENTS.  189 

the  best  method  is  to  mix  the  powdered  mineral  with  one  part  powdered 
fluorite  and  two  parts  potassium  bisulphate.  The  mixture  is  moistened 
and  placed  on  platinum  wire.  At  the  moment  of  fusion  the  green  color 
appears,  b'ut  lasts  but  a  moment  (ex.  tourmaline). 

lleated  in  a  dish  witli  sulphuric  acid,  and  alcohol  being  added  and 
ignited,  the  flames  of  the  latter  will  be  distinctly  tinged  green. 

Cadmium.  J3.B.  ;  on  charcoal  cadmium  gives  a  characteristic  sublimate 
of  the  reddish-brown  oxide  (p.  185). 

Carbonates.  Effervesce  with  dilute  hydrochloric  acid ;  many  require  to 
be  pulverized,  and  some  need  the  addition  of  heat. 

Chlorides.  B.B.  ;  if  a  small  portion  of  a  chloride  is  added  to  the  bead  of 
salt  of  phosphorus,  saturated  with  copper  oxide,  the  bead  is  instantly  sur- 
rounded with  an  intense  purplish  flame. 

In  solution  they  give  with  silver  nitrate  a  white  curdy  precipitate,  which 
darkens  in  color  on  exposure  to  the  light ;  it  is  insoluble  in  nitric  acid,  but 
entirely  so  in  ammonia. 

Chromium.  B.B.  ;  chromium  gives  with  borax  and  salt  of  phosphorus  an 
emerald-green  bead  (p.  186). 

Cobalt.  B.B. ;  a  beautiful  blue  bead  is  obtained  with  borax  in  both 
flames  from  minerals  containing  cobalt.  Where  sulphur  or  arsenic  is  present 
it  should  first  be  roasted  off  on  charcoal. 

Copper.  B.B.  ;  on  charcoal  the  metallic  copper  can  be  reduced  from 
most  of  its  compounds.  With  borax  it  gives  a  green  bead  in  the  oxidizing 
flame,  and  in  the  reducing  an  opaque  red  bead  (p.  186). 

Most  metallic  compounds  are  soluble  in  nitric  acid.  Ammonia  produces 
a  green  precipitate  in  the  solution,  which  is  dissolved  when  an  excess  is 
added,  the  solution  taking  an  intense  blue  color. 

Fluorine.  B.B. ;  heated  in  the  closed  tube  fluorides  give  off  fumes  of 
hydrofluoric  acid,  which  react  acid  with  test-paper  and  etch  the  glass. 
Sometimes  potassium  bisulphate  must  be  added  (see  also  p.  185). 

Heated  gently  in  a  platinum  crucible  with  sulphuric  acid,  most  com- 
pounds give  off  hydrofluoric  acid,  which  corrodes  a  glass  plate  placed 
over  it. 

Iron.  B.B. ;  with  borax  iron  gives  a  bead  (O.F.)  which  is  yellow  while 
hot,  but  is  colorless  on  cooling;  R.F.,  becomes  bottle-green  (see  p.  186). 
On  charcoal  with  soda  gives  a  magnetic  powder.  Minerals  which  contain 
even  a  small  amount  of  iron,  yield  a  magnetic  mass  when  heated  in  the 
reducing  flame. 

L<ad.  B.B. ;  with  soda  on  charcoal  a  malleable  globule  of  metallic  lead 
is  obtained  from  lead  compounds  ;  the  coating  has  a  yellow  color  near  the 
assay  and  farther  off  a  white  color  (carbonate) ;  on  being  touched  with  the 
reducing  flame  both  of  these  disappear,  tinging  the  flame  azure  blue. 

In  solutions  dilute  sulphuric  acid  gives  a  white  precipitate  of  lead  sul- 
phate ;  when  delicacy  is  required  an  excess  of  the  acid  is  added,  the  solution 
evaporated  to  dryness,  and  water  added,  the  lead  sulphate,  if  present,  will 
then  be  left  as  a  residue. 

Lime.  B.B. ;  it  imparts  a  yellowish-red  color  to  the  flame.  In  the  pres- 
ence of  other  alkaline  earths  the  spectroscope  gi  ves  a  sure  means  of  detecting 
even  when  in  small  quantities.  Many  lime  salts  give  an  alkaline  reaction 
with  test-paper  after  ignition. 


190  CHEMICAL   MINERALOGY. 

In  solutions  containing  lime  salts,  even  when  dilute,  ammonium  oxalate 
throws  down  a  white  precipitate  of  calcium  oxalate. 

Lithia.  B.B.  ;  lithia  gives  an  intense  red  to  the  outer  flame;  in  very  small 
quantities  it  is  evident  in  the  spectroscope. 

Magnesia.  B  B.  ;  moistened,  after  heating,  with  cobalt  nitrate  and  again 
ignited,  a  pink  color  is  obtained  from  infusible  minerals. 

Manganese.  B.B. ;  with  borax  manganese  gives  a  bead  violet-red  (O.F.), 
and  colorless  (R.F.).  With  soda  (O.F.)  it  gives  a  bluish-green  bead  ;  this 
reaction  is  very  delicate  and  may  be  relied  upon,  even  in  presence  of  almost 
any  other  metal. 

Mercury.  B.B. ;  in  the  closed  tube  a  sublimate  of  metallic  mercury  is 
yielded  when  the  mineral  is  heated  with  soda.  Mercuric  sulphide  gives  a 
black  lustreless  sublimate  in  the  tube,  red  when  rubbed  (p.  185). 

Molybdenum.  B.B.  ;  on  charcoal  molybdenum  gives  a  copper-red  stain 
(O.F.)  which  becomes  azure-blue  when  for  a  moment  touched  with  the  R.F. 
(p.  186). 

Nickel.  B.B. ;  with  borax  nickel  oxide  gives  a  bead  which  (O.F.)  is  violet 
when  hot  and  red-brown  on  cooling ;  (R.F.)  the  glass  becomes  gray  and 
turbid  from  the  separation  of  metallic  nickel,  and  on  long  blowing  colorless. 

Nitrates.  Detonate  when  heated  on  charcoal.  Heated  in  a  tube  with 
sulphuric  acid  give  off  red  fumes  of  nitric  peroxide. 

Phosphates.  B.B. ;  most  phosphates  impart  a  green  color  to  the  flame, 
especially  after  having  been  moistened  with  sulphuric  acid,  though  this  test 
may  be  rendered  unsatisfactory  by  the  presence  of  other  coloring  agents. 
If  they  are  used  in  the  closed  tube  with  a  fragment  of  metallic  magnesium  or 
sodium,  and  afterward  moistened  with  water,  phosphuretted  hydrogen  is 
given  off,  recognizable  by  its  disagreeable  odor. 

A  few  drops  of  a  neutral  or  acid  solution,  containing  phosphoric  acid, 

Eroduces  in  a  solution  of  ammonium  molybdate  with  nitric  acid  a  pulveru- 
mt  yellow  precipitate. 

Potash.  B.B. ;  potash  imparts  a  violet  color  to  the  flame  when  alone. 
It  is  best  detected  in  small  quantities,  or  when  soda  or  lithia  is  present,  by 
the  aid  of  the  spectroscope. 

Selenium.  B.B.  ;  on  charcoal  selenium  fuses  easily,  giving  off  brown 
fumes  with  a  peculiar  disagreeable  organic  odor  (see  also  p.  185). 

Silica.  B.B. ;  a  small  fragment  of  a  silicate  in  the  salt  of  phosphorus 
bead  leaves  a  skeleton  of  silica,  the  bases  being  dissolved. 

If  a  silicate  in  a  fine  powder  is  fused  with  sodium  carbonate  and  the  mass 
then  dissolved  in  hydrochloric  acid  and  evaporated  to  dryness,  the  silica  is 
made  insoluble,  and  when,  strong  hydrochloric  acid  is  added  and  then  water, 
the  bases  are  dissolved  and  the  silica  left  behind. 

Many  silicates,  especially  those  which  are  hydrous,  are  decomposed  by 
strong  hydrochloric,  acid,  tha  silica  separating  as  a  powder  or  as  a  jelly 
(see  p.  181). 

/Silver.  B.B. ;  on  charcoal  in  O.F.  silver  gives  a  brown  coating  (p.  185). 
A  globule  of  metallic  silver  may  generally  be  obtained  by  heating  on  char- 
coal in  O.F.,  especially  if  soda  is  added.  Under  some  circumstances  it  is 
desirable  to  have  recourse  to  cupel lation. 

From  a  solution  containing  any  salt  of  silver,  the  insoluble  chloride  is 
thrown  down  when  hydrochloric  acid  is  added.  This  precipitate  is  insoluble 


DETERMINATIVE  MINERALOGY.  191 

in  acid  or  water,  but  entirely  so  in  ammonia.  It  changes  color  on  exposure 
to  the  light. 

Soda.  B.B. ;  gives  a  strong  yellow  flame. 

Sulphur,  sulphides,  sulphates.  B.B. ;  in  the  closed  tube  some  sulphides 
give  off  sulphur,  others  sulphurous  oxide  which  reddens  a  strip  of  moistened 
litmus  paper.  In  small  quantities,  or  in  sulphates,  it  is  best  detected  by 
fusion  on  charcoal  with  soda.  The  fused  mass,  when  sodium  sulphide  has 
thus  been  formed,  is  placed  on  a  clean  silver  coin  and  moistened  ;  a  distinct 
black  stain  on  the  silver  is  thus  obtained  (the  precaution  mentioned  on 
p.  187  must  be  exercised). 

A  solution  in  hydrochloric  acid  gives  with-  barium  chloride  a  white  in- 
soluble precipitate  of  barium  sulphate. 

Tellurium.  B.B.  ;  tellurides  heated  in  the  open  tube  give  a  white  or 
grayish  sublimate,  fusible  to  colorless  drops  (p.  185).  On  charcoal  they 
give  a  white  coating  and  color  the  R.F.  green. 

Tin.  B.B ;  minerals  containing  tin,  when  heated  on  charcoal  with  soda 
or  potassium  cyanide,  yield  metallic  tin  in  minute  globules  (see  also  p.  187). 

Titanium.  B.B.  ;  titanium  gives  a  violet  color  to  the  salt  of  phosphorus 
bead.  Fused  with  sodium  carbonate  and  dissolved  with  hydrochloric  acid, 
and  heated  with  a  piece  of  metallic  tin  or  zinc,  the  liquid  takes  a  violet 
color,  especially  after  partial  evaporation. 

Tungsten.  B.B. ;  tungsten  oxide  gives  a  blue  color  to  the  salt  of  phos- 
phorus bead  (R.F.).  Fused  and  treated  as  titanic  acid  (see  above)  with  the 
addition  of  zinc  instead  of  tin,  gives  a  fine  blue  color. 

Uranium.  B.B. ;  salt  of  phosphorus  bead,  in  O.F.,  a  greenish-yellow 
bead  when  cool.  In  R.F.  a  fine  green  on  cooling  (p.  187). 

Vanadium.  B.B. ;  the  characteristic  reactions  of  vanadium  with  the 
fluxes  are  given  on  p.  186. 

Zinc.  B.B. ;  on  charcoal  compounds  of  zinc  give  a  coating  which  is  yel- 
low-white hot  and  white  on  cooling,  and  moistened  by  the  cobalt  solution 
and  again  heated  becomes  a  fine  green  (p.  185). 

Zirconia.  A  dilute  hydrochloric  acid  solution,  containing  zirconia,  im- 
parts an  orange-yellow  color  to  turmeric  paper,  moistened  by  the  solution. 

Students  who  desire  to  become  thoroughly  acquainted  with  the  use  of  the 
blowpipe  should  provide  themselves  with  a  thorough  and  systematic  book 
devoted  to  the  subject.  The  most  complete  American  book  is  that  by  Prof. 
Brush  (Manual  of  Determinative  Mineralogy,  with  an  introduction  on  blow- 
pipe analysis,  New  York,  1875).  Other  standard  works  are  those  of  Ber- 
zelius  (The  use  of  the  Blowpipe  in  Chemistry  and  Mineralogy,  translated  into 
English  by  Prof.  J.  D.  Whitney,  1845),  and  Plattner  (Manual  of  Qualita- 
tive and  Quantitative  Analysis  with  the  Blowpipe,  translated  by  Prof.  H. 
B.  Cornwall,  1872).  The  work  of  Prof.  Brush  has  been  freely  used  in  the 
preparation  of  the  preceding  notes  upon  blowpipe  methods  and  reactions. 


DETERMINATIVE  MINERALOGY. 

Determinative  Mineralogy  may  be  properly  considered  under  the  general 
head  of  Chemical  Mineralogy,  since  the  determination  of  minerals  depends 


192  CHEMICAL   MINERALOGY. 

mostly  upon  chemical  tests.  But  crystallographic  and  all  physical  characters 
have  also  to  be  used. 

There  is  but  one  satisfactory  way  in  which  the  identity  of  an  unknown 
mineral  may  in  all  cases  be  fixed  beyond  question,  and  that  is  by  the  use  of 
a  complete  set  of  determinative  tables.  By  means  of  such  tables  the  mineral 
in  hand  is  referred  successively  from  a  general  group  into  a  more  special 
one,  until  at  last  all  other  species  have  been  eliminated,  and  the  identity 
of  the  one  given  is  beyond  doubt. 

A  careful  preliminary  examination  of  the  unknown  mineral  should,  how- 
ever, always  be  made  before  final  recourse  is  had  to  the  tables.  This 
examination  will  often  suffice  to  show  what  the  mineral  in  hand  is,  and  in 
any  case  it  should  not  be  omitted,  since  it  is  only  in  this  way  that  a  practi- 
cal familiarity  with  the  appearance  and  characters  of  minerals  can  be  gained. 

The  student  will  naturally  take  note  first  of  those  characters  which  are 
at  once  obvious  to  the  senses,  that  is  :  the  color ,  lustre,  feel,  general  struc- 
ture, fracture,  cleavage,  and  also  crystalline  form,  if  distinct ;  also,  if  the 
specimen  is  not  too  small,  the  apparent  weight  will  suggest  something  as  to 
the  .specific  gravity.  The  above  characters  are  of  very  unequal  importance. 
Structure,  if  crystals  are  not  present,  and  fracture  are  generally  unessential 
except  in  distinguishing  varieties ;  color  and  lustre  are  essential  with 
metallic,  but  generally  very  unimportant  with  unrnetallic  minerals.  /Streak 
is  of  importance  only  with  colored  minerals  and  those  of  metallic  lustre 
(p.  158).  Crystalline  form  and  cleavage  are  of  the  highest  importance,  but 
usually  require  careful  study. 

The  first  trial  should  be  the  determination  of  the  hardness  (for  which  end 
the  pocket-knife  is  often  sufficient  in  experienced  hands).  The  second  trial 
should  be  the  determination  of  the  specific  gravity.  Treatment  of  the 
powdered  mineral  with  acids  may  come  next ;  by  this  means  (see  p.  180) 
the  presence  of  carbonic  acid  is  detected,  and  also  other  results  obtained 
(p.  181).  Then  should  follow  blowpipe  trials,  to  ascertain  the  fusibility, 
the  color  given  to  the  flame,  if  any,  the  character  of  the  sublimate  given  off, 
and  the  reactions  with  \\\Q  fluxes  and  other  points  as  explained  in  the  pre- 
ceding pages. 

How  much  the  observer  learns  in  the  above  way,  in  regard  to  the  nature 
of  his  mineral,  depends  upon  his  knowledge  of  the  characters  of  minerals  in 
general,  and  upon  his  familiarity  with  the  chemical  behavior  of  the  vari- 
ous elementary  substances  (pp.  188  to  191)  with  reagents,  and  before  the 
blowpipe.  If  the  results  of  such  a  preliminary  examination  are  sufficiently 
definite  to  suggest  that  the  mineral  in  hand  is  one  of  a  small  number  of 
species,  reference  may  be  made  to  their  full  description  in  Part  111.  of  this 
work  for  the  final  decision. 

A  number  of  minor  tables,  embracing  under  appropriate  heads  minerals 
which  have  some  striking  physical  characters,  are  added  in  the  Appendix. 
They  will  in  many  cases  aid  the  observer  in  reaching  a  conclusion.  In 
addition  to  these  tables,  an  extended  table  is  also  given  for  the  systematic 
determination  of  the  more  important  minerals,  those  described  in  full  in 
the  following  pages.  The  admirable  tables  of  von  Kobell,  as  extended  and 
remodeled  by  Prof.  Brush  (Manual  of  Determinative  Mineralogy,  see  p. 
19J),  embracing,  as  they  do,  all  mineral  species,  will  be  found  of  the  greatest 
value,  and  should  be  in  the  hands  of  every  student. 


3PA.RT    III. 

DESCRIPTIVE  MINERALOGY. 


THE  following  is  the  system  of  classification  employed  in  the  arrangement 
of  the  species  in  this  work.     It  is  identical  with  that  adopted  in  Dana's 
System  of  Mineralogy,  1868,  to  which  treatise  reference  may  be  made  for 
the  discussion  of  the  principles  upon  which  it  is  based.     In  general  only 
the  more  prominent  species  are  enumerated  under  the  successive  heads. 
The  native  elements  are  grouped  as  follows : 
SERIES  I. — The  more  basic,  or  electro-positive  elements. 

1.  GOLD   GROUP. — Gold,   silver   (also    hydrogen,    potassium, 

sodium,  etc.). 

2.  IRON  GROUP. — Platinum,  palladium,  mercury,  copper,  iron, 

zinc,  lead  (also  cobalt,  nickel,  chromium,  manganese, 
calcium,  magnesium,  etc.). 

3.  TIN  GROUP. — Tin  (also  titanium,  zirconium,  etc.). 
SERIES  II. — Elements  generally  electro-negative. 

1.  ARSENIC  GROUP. — Arsenic,  antimony,  bismuth,  phosphorus, 

vanadium,  etc. 

2.  SULPHUR  GROUP. — Sulphur,  tellurium,  selenium. 

3.  CARBON-SILICON  GROUP. — Carbon,  silicon. 
SERIES  III. — Elements  always  negative. 

1.  Chlorine,  bromine,  iodine. 

2.  Fluorine. 

3.  Oxygen. 


CLASSIFICATION  OF  MINERAL  SPECIES. 


I.  NATIVE    ELEMENTS. 

Gold  ;  silver. — Platinum  ;  palladium  ;  iridosmine,  IrOs,  etc. ;  mercury ; 
amalgam,  AgHg,  etc. ;    copper  ;    iron. — Arsenic  ;  antimony  ;  bismuth. — 
Tellurium ;  sulphur. — Diamond  ;  graphite. 
13 


194  DESCRIPTIVE   MINERALOGY. 


II.  SULPHIDES,    TELLURIDES,    SELENIDES,    ARSEN- 
IDES, ANTIMONIDES,  BISMUTHIDES. 

1.  BINARY  COMPOUNDS.— SULPHIDES  AND  TELLURIDES  OF  METALS 
OF  THE  SULPHUR  AND  ARSENIC  GROUPS. 

(a)  Realgar  group.  Composition  RS.     Monoclinic.     Realgar. 
(fr)   Orpiment  group.   Composition  RA.    Orthorhombic.  Orpiment; 
stibnite  ;  bismuthinite. 

(c)  Tetradymite  group.  Tetradjmite  Bi2(Te,S)3. 

(d)  Molybdenite  group.  Composition  RS2.     Molybdenite, 

2.  BINARY  COMPOUNDS.— SULPHIDES,  TELLURIDES,  ETC.,  OF  METALS 
OF  THE  GOLD,  IRON,  AND  TIN  GROUPS. 

A.  BASIC  DIVISION.— Dyscrasite;  domeykite. 

B.  PHOTO  DIVISION.— Composition  RS  (or  R2S),  RSe,  RTe. 

(a)   Galenite  group.  Isometric ;    holohedral. — Argentite  ;  galenite  ; 

clausthalite  ;  bornite  ;  alabandite. 
Blende  group.  Isometric  ;  tetrahedral. — Sphalerite. 
c)   Chaleocite  group.  Orthorhombic. — Chalcocite ;    acanthite  ;    hes- 

site ;  stromeyerite. 
(d)  Pyrrhotite  group.  Hexagonal. — Cinnabar  ;    millerite  ;    pyrrho- 

tite  (Fe7S8) ;  greenockite  ;  niccolite. 

C.  DEUTO  on  PYBITE  DIVISION.— Composition  RS2,  etc. 

(a)  Pyrite  group.  Isometric. — Pyrite  ;    linnseite  ;    smaltite  ;  cobal- 

tite ;  gersdorffite. — Chalcopyrite. 

(b)  Marcasite  group.    Orthorhombic.  —  Marcasite  ;     arsenopyrite  ; 

sylvanite. 
(G)  Nagyagite.     (d)  Covellite. 

3.  TERNARY    COMPOUNDS.— SULPHARSENITES,    SULPHANTIMONITES, 

SULPHOBISMUTHITES. 

(a)  GROUP   I.    Atomic   ratio,    R  f  As(Sb)  :  S ..=  1  n  2  :  4.     Formula 

R(As,Sb)2S4  =  RS  ^(ASjSb)^,    Miargyrite  ;  sartorite  ;  zink- 

enite. 
(t>)  SUB    GROUP.    At.   Ratio,   R  :  As(Sb)  :  S  =  3  :  4  :  9.      Formula 

Rj(4s,Sb,Bi)4S9  =  3RS  +  2(As,Sb,Bi)2S3.     Jordanite  ;   scliir- 

merite,  etc. 

(c)  GROUP   II.    At.   Ratio,   R  :  (As,  Sb)  :  S  =  2  :  2  :  5.      Formula 

R/Sb, As)2S5  =  2RS  -f  (Sb,As)2S3.      Jamesonite  ;  4uf renoysite. 

(d)  GROUP   III.  At,  Ratio,   R  :  (As,Sb)  :  S  =(3  :  2:6.)     Formula 

Rs(As,Sb)2S6  =  3RS  -f  (AsjSb)^.       Pyrargynte,     proustite  ; 
bournonite ; 


CLASSIFICATION   OF    SPECIES.  195 

(e)  GROUP  IY.  At.  Katio,  R  :  (As,Sb,Bi)  :  S  =  4  :  2  :  7.  Formula 
R4(As,Sb,Bi)2S7  =  4rRS  +  (As,Sb,Bi)2S3.  Tetrahedrite ;  ten- 
nantite. 

(/)  GROUP   Y.    At.   Katio,    R  :  (As,Sb)  :  S  =  5  :  2  :  8.      Formula 

R5(As,Sb)2S8  =  5RS-h(As,Sb)2S3.     Stephanite  ;    geocronite. 
Polybasite. — Enargite. 


III.  CHLORIDES,  BROMIDES,  IODIDES. 

1.  ANHYDROUS    CHLORIDES.— Composition  mostly  E(C1,  Br,  I)  ; 
also  R^ClBr,!)  (calomel),  and  RC16  (molysite). 

Halite  ;  svlvite  ;  cerargyrite  ;  embolite  ;  bromyrite. 

2.  HYDROUS  CHLORIDES.— Carnallite.     Tachhydrite. 

3.  OXYCHLORIDES,— Atacamite  ;  matlockite. 


IV.  FLUORIDES. 

1.  ANHYDROUS  FLUORIDES.     Fluorite ;  sellaite.— Cryolite. 

2.  HYDROUS  FLUORIDES.— Pachnolite ;  ralstonite. 


V.  OXYGEN  COMPOUNDS. 

I.  OXIDES. 

1.  OXIDES  OF  METALS  OF  THE  GOLD,  IRON,  AND  TIN  GROUPS. 

A.  ANHYDROUS  OXIDES.—  (a)   PROTOXIDES.—  Binary   compounds   of 

oxygen  with   a  univalent  or  bivalent  element.     Formula   RO  or  (R^O). 
Cuprite  ;  zincite  ;  tenorite. 

(b)  SESQUIOXIDES.  —  Binary  compounds  of  oxygen  with  a  sexivalent  ele- 
ment.    Formula  RO3.     Corundum;  hematite.     This  group  also  includes 
menaccanite  and  perofskite. 

(c)  COMPOUNDS  OF  PROTOXIDES  AND  SESQUIOXIDES.  —  Ternary  compounds 
of  oxygen  with  a  bivalent  and  a  sexivalent  element.     Formula  RRO4  =  RO 


Spinel  Group.  Isometric.  —  Spinel  ;  gahnite  ;  magnetite  ;  franklinite  ; 
chromite.  Hexagonal.  —  Chrysoberyl. 

(d)  DEUTOXIDES.  —  Binary  compounds  of  oxygen  with  a  quadrivalent  ele- 
metit.  Formula  RO2. 

TETRAGONAL.  —  Rutile  Group.  —  Cassiterite  ;  rutile  ;  octahedrite  ;  haus- 
mannite  ;  braunnite.  Orthorhombic.  —  Brookite  ;  pyrolusite. 

B.  HYDROUS  OXIDES.—  Turgite.—  Diaspore  ;  gothite  ;  manganite.— 
Limonite.—  Brucite  ;  gibbsite.  —  Psilomelane. 


196  DESCRIPTIVE   MINERALOGY. 

2.  OXIDES  OF  METALS  OF  THE  ARSENIC  AND  SULPHUR  GROUPS. 
Isometric. — Arsenolite ;     senarmontite.       Orthorhombic.  —  Claudetite  ; 

valentinite ;  bismite,  etc. 

3.  OXIDES  OF  THE   CARBON-SILICON   GROUP. — Quartz ;    tridymite  ;    as- 
manite ;  opal. 

II.  TERNARY  OXYGEN  COMPOUNDS. 
1.  SILICATES. — A.  ANHYDROUS  SILICATES. 

(a)  BISILICATES. — Salts  of  meta-silicic  acid,  H2SiO3.  Quantivalent  ratio 
for  basic  elements  and  silicon,  1  :  2.  General  formula  RSiO3.  This  may 
be  written  :  R  \\  O2  |  SiO,  to  indicate  that  part  only  of  the  oxygen  is  regarded 
as  linking  oxygen,  or,  taking  into  account  the  quantivalence  of  the  various 
basic  elements  that  may  be  present,  R^  aR,  /3R  ||  O2  ||  SiO. 

(a)  Amphibole  group.   Pyroxene  section  (f/\  1=  86°-88°).    Orthorhom- 
bic. —  Eristatite  ;    hypersthene.      Monoclinic.  —  Wollastonite  ;    pyroxene  ; 
acmite  ;     segirite.      Triclinic. — Rhodonite  ;    babingtonite.  —  Spodumene  ; 
petalite. 

(b)  Amphibole  section  (I A  I—  123°-125°).    Orthorhombic.— Anthophyl- 
lite,  kupft'erite.     Monoclinic,  amphibole  ;  arf  vedsonite. 

Beryl.     Eudialjte.     Pollucite. 

(/3)  UNISILICATES. — Salts  of  the  normal  silicic  acid,  H4SiO4.  Quantivalent 
ratio  for  basic  elements  and  silicon,  1  :  1.  General  formula  R2SiO4.  This 
may  be  written  :  R2  J  O4  j  Si,  to  show  that  all  the  oxygen  is  regarded  as 
linking  oxygen,  or,  R^aR,  /SR  ||  O4  [  Si.  The  latter  formula  shows  that, 
though  elements  of  different  quanti valence  ^inay  be  present,  the  same  uni- 
silicate  type  still  exists.  The  excess  of  silica  sometimes  present  in  both 
bisilicates  and  unisilicates,  as  well  as  other  deviations  from  the  ordinary 
types,  are  remarked  upon  in  the  pages  which  follow. 

(a)  Chrysolite  group.  Orthorhombic,  /A  7=  91°-95°  ;  0  A 14  =  124°- 
129°. — Chrysolite,  forsterite,  tephroite,  monticellite,  etc. 

'  (b)    Willemite  group.  Hexagonal,  RAR  =  116°-117°.— Willemite,  diop- 
tase,  phenacite. 

(c)  Isometric.     Helvite.     Danalite,  R?SiO4  +  RS. 

(d)  Garnet  group.  Isometric. — Q.  ratio  for  R  :  IB  :  Si  =  1  :  1  :  2.     Gen- 
eral formula  R3RSi3O12. 

(e)  Vesuvianite  group.  Tetragonal. — Zircon,  vesuvianite. 

(/)  Epidote  group.  Anisometric. — Epidote  ;  allanite  ;  zoisite  ;  gadoli- 
nite  ;  ilvaite. 

(g)  Triclinic.     Axinite.     Danburite. — (A)  lolite. 

(k)  Mica  group.  /A  1  =120°.  Cleavage  basal  perfect;  optic  axis  or 
acute  bisectrix  normal  to  the  cleavage-plane. — Phlogopite  ;  biotite ;  lepido- 
melane  ;  mnscovite  ;  lepidolite. 

(1)  Scapolite  group.  Tetragonal. — Sarcolite  ;  meionite  ;  wernerite  ; 
ekebergite. 

(m)  Hexagonal.  Nephelite.  Isometric. — Sodalite  ;  hailynite  ;  nosite ; 
leucite. 


CLASSIFICATION   OF    SPECIES.  197 

Feldspar  group.  Monoclinic  or  triclinic.  /A  ./"near  120°  ;  Q.  ratio  for 
B  :  ft  =  1  :  3.  Anorthite  ;  labradorite  ;  andesite  ;  hyalophane  ;  oligo- 
clase  ;  albite  ;  orthoclase  (microcline). 

(7)  SUBSILICATES. — (a)  Q.  ratio  for  bases  to  silicon,  4  :  3.  Chondrodite. 
Tourmaline. 

(b)  Q.  ratio  for  bases  to  silicon,  3  :  2.  Genlenite. — Andalusite ;  fibrolite  ; 
cyanite  (AlSiO6). — Topaz  ;  euclase  ;  datolite. — Guarinite  ;  titanite  ;  keil- 
hauite ;  tscheffkinite. 

(o)  Q.  ratio  for  bases  to  silicon,  2:1.     Staurolite. 

B.  HYDROUS  SILICATES — GENERAL  SECTION. 

BISILICATES. — Pectolite  ;  laumontite  ;  okenite. — Chrysocolla  ;  alipite,  etc. 
UNISILICATES. — Calauiine ;  prehnite. — Thorite.     Pyroemalite.— Apophyl- 
lite. 

SUBSILICATES. — Allopliane. 

ZEOLITE  SECTION. 

Thorasonite  ;  natrolite  ;  scolecite  ;  mesolite. — Levynite. — Analcite. — 
Chabazite  ;  gmeliiiite  ;  herschelite. — Phillipsite. — Harmotome. — Stilbite  ; 
heulandite. 

MARGAROPHYLLITE  SECTION. 

BISILICATES. — Talc.     Pyrophyllite. — Sepiolite  ;  glauconite. 

UNISILICATES. — Serpentine  group.  Serpentine  ;  deweylite  ;  genthite. 

Kaolinite  group.  .Kaolinite  ;  pholerite  ;  halloysite. 

Pinite  group.  Finite,  etc. ;  palagonite. 

Hydro-mica  group.  Fahlunite  ;  margarodite  ;  damourite  ;  paragonite  ; 
cookeite. — Hisingerite. 

Chlorite  group.  Yermiculites,  Q.  ratio  of  bases  to  silicon,  1:1.  Pyro- 
sclerite ;  jefferisite,  etc. — Penninite. — Kipidolite  ;  prochlorite. — Chloritoid ; 
margarite.  Seybertite. 


2.  TANTALATES,  COLUMBATES. 

Pyrochlore. — Tantalite  ;    columbite  ;   yttrotantalite  ;    samarskite ;  enxe- 
nite ;  seschynite,  etc. 


3.  PHOSPHATES,  ARSENATES,  VANADATES. 

ANHYDEOUS. — Xenotime  YSP2O8 ;  pucherite. — Descloizite. 
Hexagonal. — Formula  S^P, As, V)2O8+R(C1,F)2.      Apatite;    pyromor- 
phite  ;    mimetite ;  vanadinite. 

Wagnerite  ;  monazite. — Triphylite  ;  triplite. — Amblygonite  (hebronite). 


198  DESCRIPTIVE   MINERALOGY. 

HYDROUS. — Pharmacolite ;  brushite. — Yivianite  ;  erythrite. — Libethinite; 
olivenite. — Liroconite  ;  pseudomalachite. — Clinoclasite. — Lazulite  ;  scoro- 
dite  ;  wavellite  ;  pharmacosiderite. — Childrenite. — Turquois  ;  cacoxenite. 
— Torbernite ;  autunite. 

Hydrous  antimonate. — Bindheiinite. 


4.  BORATES. 

Sassolite  ;    sussexite  ;    ludwigite. — Boracite  ;    ulexite  ;    price! te. — War- 
wickite. 


5.   TUNGSTATES,    general    formula    RWO4 ;    MOLYBDATES,   EMoO4; 

CHROMATES,  KCrO4. 

Wolframite ;  scheelite ;  stolzite. — Wulfenite. — Crocoite ;  phoenicochroite. 


6.    SULPHATES. 

ANHYDROUS.  —  General  formula  RSO4.    Orthorhombic  7"  A  /  =  100°—  105°. 
Barite  ;  celestite  ;  anhydrite  ;  anglesite  ;  zinkosite  ;  leadliillite. 
Caledonite.  —  Dreelite  ;  susannite  ;  connellite.  —  Glauberite  ;  lanarkite. 
HYDROUS  SULPHATES.  —  Mirabilite.  —  Gypsum.  —  Polyhalite.  —  Epsomite. 
Copperas   group.    Chalcanthite,   CuSO4  +  5aq,   also  the   other   vitriols, 


Copiapite.-  —  Aluminite.  —  Linarite  ;  brochantite,  etc. 
TELLURATES.  —  Montanite,  Bi2TeO6  -f  2aq. 


7.  CARBONATES. 

ANHYDROUS. —  Calcite  group.  Rhombohedral.  General  formula,  KCO3. 
— Calcite  ;  dolomite  ;  magnesite  ;  siderite  ;  rhodochrosite  ;  smithsonite. 

Aragonite  group.  Orthorhombic. — Aragonite  ;  witherite  ;  strontianite  ; 
cerussite  ;  baryto-calcite. — Phosgenite. 

HYDROUS  CARBONATES. — Gaylussite, — Hydromagnesite.  —  Hydrozincite  ; 
malachite  ;  azurite. — Bismutite,  etc. 


VI.  HYDROCARBON  COMPOUNDS. 


I.  NATIVE  ELEMENTS. 

GOLD. 

Isometric.  The  octahedron  and  dodecahedron  the  most  common  forms. 
Crystals  sometimes  acicular  through  elongation  of  octa-  415 

hedral  or  other  forms  ;  also  passing  into  filiform,  reti- 
culated, and  arborescent  shapes  ;  and  occasionally 
spongiform  from  an  aggregation  of  filaments  ;  edges  of 
crystals  often  salient  (f.  415).  Cleavage  none.  Twins :  ' 
twinning-plane  octahedral.  Also  massive  and  in  thin 
laminae.  Often  in  flattened  grains  or  scales,  and  rolled 
masses  in  sand  or  gravel. 

H.=:2-5-3.     G.=15-6-19-5;  19-30-19-34,  when  quite 
pure,  G.    Rose.      Lustre    metallic.      Color    and  streak 
various  shades  of  gold-yellow,  sometimes  inclining  to  silver-white.     Very 
ductile  and  malleable. 

Composition,  Varieties. — Gold,  but  containing  silver  in  different  proportions,  and  some- 
times also  traces  of  copper,  iron,  bismu-th  (maldonite),  palladium,  rhodium.  Var.  1.  Ordinary. 
Containing  0'1(>  to  16  p.  c.  of  silver.  Color  varying,  accordingly,  from  deep  gold -yellow  to 
pale  yellow;  Q-.  =10-15*5.  2.  Argentiferous;  Electrum.  Color  pale  yellow  to  yellowish- 
white  ;  G.  =  15  '5-12  '5.  Ratio  for  the  gold  and  silver  of  1  :  1  corresponds  to  35  '5  p.  c.  of  silver, 
2  :  1,  to  21 -6  p.  c. 

The  average  proportion  of  gold  in  the  native  gold  of  California,  as  derived  from  assays  of 
several  hundred  millions  of  dollars'  worth,  is  880  thousandths  ;  while  the  range  is  mostly 
between  870  and  890  (Prof.  J.  C.  Booth,  of  U.  S.  Mint).  The  range  in  the  metal  of  Australia 
is  mostly  between  900  and  960,  with  an  average  of  925.  The  gold  of  the  Chaudiere,  Canada, 
contains  usually  10  to  15  p  c.  of  silver  ;  while  that  of  Nova  Scotia  is  very  nearly  pure.  The 
Chilian  gold  afforded  Domeyko  84  to  96  per  cent,  of  gold  and  15  to  3  per  cent,  of  silver. 
(Ann.  d.  Mines,  IV.  vi. ) 

Pyrogiiostic  and  other  Chemical  Characters. — B.B.  fuses  easily.  Not  acted  on  by  fluxes. 
Insoluble  in  any  single  acid ;  soluble  in  nitro-hydrochloric  acid  (aqua-regia). 

D  ff. — Readily  recognized  by  its  malleability  and  specific  gravity.  Distinguished  by  its 
insolubility  in  nitric  acid  from  pyrite  and  chalcopyrite. 

Observations.— Native  gold  is  found,  when  in  situ,  with  comparatively  small  exceptions, 
in  the  quartz  veins  that  intersect  metamorphic  rocks,  and  to  some  extent  in  the  wall  rock  of 
these  veins.  The  metamorphic  rocks  thus  intersected  are  mostly  chloritic,  talcose,  and 
argillaceous  schisb  of  dull  green,  dark  gray,  and  other  colors  ;  also,  much  less  commonly, 
mica  and  hornblendic  schist,  gneiss,  dioryte,  porphyry ;  and  still  more  rarely,  granite.  A 
laminated  quartzyte,  called  itacolumyte,  is  common  in  many  gold  regions,  as  those  of  Brazil 
and  North  Carolina,  and  sometimes  specular  schists,  or  slaty  rocks  containing  much  foliated 
specular  iron  (hematite),  or  magnetite  in  grains. 

The  gold  occurs  in  the  quartz  in  strings,  scales,  plates,  and  in  masses  which  are  sometimes 
an  agglomeration  of  crystals  ;  and  the  scales  are  often  invisible  to  the  naked  eye,  massive 
quartz  that  apparently  contains  no  gold  frequently  yielding  a  considerable  percentage  to  the 
assay er.  It  is  always  very  irregularly  distributed,  and  never  in  continuous  pure  bands  of 
metal,  like  many  metallic  ores.  It  occurs  both  disseminated  through  the  mass  of  the  quartz, 
and  in  its  cavities.  The  associated  minerals  are  :  pyrite,  which  far  exceeds  in  quantity  all 
others,  and  is  generally  auriferous ;  next,  chalcopyrite,  galenite,  sphalerite,  arsenopyrite, 
each  frequently  auriferous  ;  often  tetradymite  and  other  tellurium  ores,  native  bismuth,  stib- 
nite,  magnetite,  hematite ;  sometimes  barite,  apatite,  fluorite,  siderite,  chrysocolla. 

The  gold  of  the  world  has  been  mostly  gathered,  not  directly  from  the  quartz  veins,  but 


200  DESCRIPTIVE   MINERALOGY. 

from  the  gravel  or  sands  of  rivers  or  valleys  in  auriferous  regions,  or  the  slopes  of  mountains 
or  hills,  whose  rocks  contain  in  some  part,  and  generally  not  far  distant,  auriferous  veins ; 
such  mines  are  often  called  alluvial  washings  ;  in  California  placer-diggings.  Most  of  the  gold 
of  the  Urals,  Brazil,  Australia,  and  all  other  gold  regions,  has  come  from  such  alluvial  wash- 
ings. The  alluvial  gold  is  usually  in  flattened  scales  of  different  degrees  of  fineness,  the  size 
depending  partly  on  the  original  condition  in  the  quartz  veins,  and  partly  on  the  distance  to 
which  it  has  been  transported.  Transportation  by  running  water  is  an  assorting  process  ;  the 
coarser  particles  or  largest  pieces  requiring  rapid  currents  to  transport  them,  and  dropping 
first,  and  the  finer  being  carried  far  away — sometimes  scores  of  miles.  A  cavity  in  the  rocky 
slopes  or  bottom  of  a  valley,  or  a  place  where  the  waters  may  have  eddied,  generally  proves 
in  such  a  region  to  be  a  pocket  full  of  gold. 

In  the  auriferous  sands,  crystals  of  zircon  are  very  common  ;  also  garnet  and  cyanite  in 
grains;  often  also  monazite,  diamonds,  topaz,  magnetite,  corundum,  iridosmine,  platinum. 
The  zircons  are  sometimes  mistaken  for  diamonds. 

Gold  exists  more  or  less  abundantly  over  all  the  continents  in  most  of  the  regions  of  crystal- 
line rocks,  especially  those  of  the  semi- crystalline  schists ;  and  also  in  some  of  the  large 
islands  of  the  world  where  such  rocks  exist.  In  Europe,  it  is  most  abundant  in  Hungary  and 
•  in  Transylvania  ;  it  occurs  also  in  the  sands  of  the  Rhine,  the  Reuss,  the  Aar,  the  Rhone,  and 
the  Danube  ;  on  the  southern  slope  of  the  Pennine  Alps,  from  the  Sim.plon  and  Monte  Rosa 
to  the  valley  of  Aosta ;  in  Piedmont ;  in  Spain,  formerly  worked  in  Asturias  ;  in  many  of  the 
streams  of  Cornwall ;  near  Dolgelly  and  other  parts  of  North  Wales  ;  in  Scotland  ;  in  the 
county  of  Wicklow,  Ireland  ;  in  Sweden,  at  Edelfors. 

In  Asia,  gold  occurs  along  the  eastern  flanks  of  the  Urals  for  500  miles,  and  is  especially 
abundant  at  the  Beresov  mines  near  Katharinenburg  (lat.  56°  40'  1ST.) ;  also  obtained  at  Petro- 
pavlovski  (60°  N.) ;  Nischne  Tagilsk  (59°  N.)  ;  Miask,  near  Slatoust  and  Mt.  Ilmen  (55°  N., 
where  the  largest  Russian  nugget  was  found),  etc.  Asiatic  mines  occur  also  in  the  Cailas 
Mountains,  in  Little  Thibet,  Ceylon,  and  Malacca,  China,  Corea,  Japan,  Formosa,  Sumatra, 
Java,  Borneo,  the  Philippines,  and  other  East  India  Islands. 

In  Africa,  gold  occurs  at  Kordofan,  between  Darfour  and  Abyssinia  ;  also,  south  of  the 
Sahara  in  Western  Africa,  from  the  Senegal  to  Cape  Palmas  ;  in  the  interior,  on  the  Somat, 
a  day's  journey  from  Cassen  ;  along  the  coast  opposite  Madagascar,  between  22°  and  35°  S., 
supposed  by  some  to  have  been  the  Ophir  of  the  time  of  Solomon. 

In  South  America,  gold  is  found  in  Brazil ;  in  New  Granada  ;  Chili ;  in  Bolivia  ;  sparingly 
in  Peru.  Also  in  Central  America,  in  Honduras,  San  Salvador,  Guatemala,  Costa  Rica,  and 
near  Panama  ;  most  abundant  in  Honduras. 

In  North  America,  there  are  numberless  mines  along  the  mountains  of  Western  America, 
and  others  along  the  eastern  range  of  the  Appalachians  from  Alabama  and  Georgia  to  Labra- 
dor, besides  some  indications  of  gold  in  portions  of  the  intermediate  Archean  region  about 
Lake  Superior.  They  occur  at  many  points  along  the  higher  regions  of  the  Rocky  Mountains, 
in  Mexico,  and  in  New  Mexico,  in  Arizona,  in  the  San  Francisco,  Wauba,  Yuma,  and  other 
districts  ;  in  Colorado,  abundant,  but  the  gold  largely  in  auriferous  pyrite  ;  in  Utah,  and 
Idaho,  and  Montana.  Also  along  ranges  between  the  summit  and  the  Sierra  Nevada,  in  the 
Humboldt  region  and  elsewhere.  Also  in  the  Sierra  Nevada,  mostly  on  its  western  slope 
(the  mines  of  the  eastern  being  principally  silver  mines).  The  auriferous  belt  may  be  said  to 
begin  in  the  Calif ornian  peninsula.  Near  the  Tejon  pass  it  enters  California,  and  beyond  for 
180  miles  it  is  sparingly  auriferous,  the  slate  rocks  being  of  small  breadth ;  but  beyond  this, 
northward,  the  slates  increase  in  extent,  and  the  mines  in  number  and  productiveness,  and 
they  continue  thus  for  200  miteiS  or  more.  Gold  occurs  also  in  the  Coast  ranges  in  many 
localities,  but  mostly  in  too  small  quantities  to  be  profitably  worked.  The  regions  to  the 
north  in  Oregon  and  Washington  Territory,  and  the  British  Possessions  farther  north,  as  also 
our  possessions  in  Alaska,  are  at  many  points  auriferous,  and  productively  so,  though  to  a 
less  extent  than  California. 

In  eastern  North  America,  the  mines  of  the  Southern  United  States  produced  before  the 
California  discoveries,  in  1849,  about  a.  million  of  dollars  a  year.  They  are  mostly  confined 
to  the  States  of  Virginia,  North  and  South  Carolina,  and  Georgia,  or  along  a  line  from  the 
Rappahannock  to  the  Coosa  in  Alabama.  But  the  region  may  be  said  to  extend  north  to 
Canada ;  for  gold  has  been  found  at  Albion  and  Madrid  in  Maine  ;  Canaan  and  Lisbon,  N.  H.  ; 
Bridgewater,  Vermont ;  Dedham,  Mass.  Traces  occur  also  in  Franconia  township,  Mont- 
gomery Co. ,  Pennsylvania.  In  Canada,  gold  occurs  to  the  south  of  the  St.  Lawrence,  in  the 
soil  on  the  Chaudiere,  and  over  a  considerable  region  beyond.  In  Nova  Scotia,  mines  are 
worked  near  Halifax  and  elsewhere. 

In  Australia,  which  is  fully  equal  to  California  in  productiveness,  and  much  superior  in  the 
purity  of  the  metal,  the  principal  gold  mines  occur  along  the  streams  in  the  mountains  of 
N.  S.  Wales  (S.  E.  Australia),  and  along  the  continuation  of  the  same  range  in  Victoria 
(S.  Australia). 


NATIVE   ELEMENTS.  201 


SILVER. 

Isometric.  Cleavage  none.  Twins :  twinning-plane  octahedral.  Com- 
monly coarse  or  fine  filiform,  reticulated,  arborescent ;  in  the  latter,  the 
branches  pass  off  either  (1)  at  right  angles,  and  are  crystals  (usually  octa- 
hedrons) elongated  in  the  direction  of  a  cubic  axis,  or  else  a  succession  of 
partly  overlapping  crystals ;  or  (2)  at  angles  of  60°,  they  being  elongated  in 
the  direction  of  a  dodecahedral  axis.  Crystals  generally  obliquely  pro- 
longed or  shortened,  and  thus  greatly  distorted.  Also  massive,  and  in 
plates  or  superficial  coatings. 

H.=2-5-3.  G.—  lO-1-ll-l,  when  pure  1O5.  Lustre  metallic.  Color 
and  streak  silver- white ;  subject  to  tarnish,  by  which  the  color  becomes 
grayish-black.  Ductile. 

Comp.,  Var. — Silver,  with  some  copper,  gold,  and  sometimes  platinum,  antimony,  bismuth, 
mercury. 

Ordinary,  (a)  crystallized;  (b)  filiform,  arborescent;  (c)  massive.  Auriferous.  Contains 
10  to  30  p.  c.  of  gold  ;  color  white  to  pale  brass-yellow.  There  is  a  gradual  passage  to  argen- 
tiferous gold.  Cupriferous.  Contains  sometimes  10  p.  c.  of  copper. 

Pyr.,  etc. — B.B.  on  charcoal  fuses  easily  to  a  silver- white  globule,  which  in  O.F.  gives  a 
faint  dark-red  coating  of  the  oxide  ;  crystallizes  on  cooling.  Soluble  in  nitric  acid,  and 
deposited  again  by  a  plate  of  copper. 

Obs. — Native  silver  occurs  in  masses,  or  in  arborescent  and  filiform  shapes,  in  veins  travers- 
ing gneiss,  schist,  porphyry,  and  other  rocks.  Also  occurs  disseminated,  but  usually  invisibly, 
in  native  copper,  galenite,  chalcocite,  etc. 

The  mines  of  Kongsberg,  in  Norway,  have  afforded  magnificent  specimens  of  native  silver. 
The  principal  Saxon  localities  are  at  Freiberg,  Schneeberg,  and  Johanugeorgenstadt ;  the 
Bohemian,  at  Przibram,  and  Joachimsthal.  It  also  occurs  in  small  quantities  with  other  ores, 
at  Andreasberg,  in  the  Harz  ;  in  Suabia ;  Hungary ;  at  Allemont  in  Dauphiny  ;  in  the 
Ural  near  Beresof  ;  in  the  Altai,  at  Zmeoff  ;  and  in  some  of  the  Cornish  mines. 

Mexico  and  Peru  have  been  the  most  productive  countries  in  silver.  In  Mexico  it  has 
been  obtained  mostly  from  its  ores,  while  in  Peru  it  occurs  principally  native.  In  Durango, 
Sinaloa,  and  Sonora,  in  Northern  Mexico,  are  noted  mines  affording  native  silver. 

In  the  United  States  it  is  disseminated  through  much  of  the  copper  of  Michigan,  occasion- 
ally in  spots  of  some  size,  and  sometimes  in  cubes,  skeleton  octahedrons,  etc. ,  at  various 
mines.  In  Idaho,  at  the  "'Poor  Man's  lode,"  large  masses  of  native  silver  have  been  ob- 
tained. In  Nevada,  in  the  Comstock  lode,  it  is  rare,  and  mostly  in  filaments  ;  at  the  Ophir 
mine  rare,  and  disseminated  or  filamentous  ;  in  California,  sparingly,  in  Silver  Mountain  dis- 
trict, Alpine  Co. ;  in  the  Maris  vein,  in  Los  Angeles  Co.  ;  in  the  township  of  Ascot,  Canada. 


PLATINUM. 

Isometric.  Karely  in  cubes  or  octahedrons.  Usually  in  grains ;  occa- 
sionally in  irregular  lumps,  rarely  of  large  size.  Cleavage  none. 

H.=4:-4-5.  G.=16-19;  17'108,  small  grains,  17-608,  a  mass,  Breith. 
Lustre  metallic.  Color  and  streak  whitish  steel-gray  ;  shining.  Opaque. 
Ductile.  Fracture  hackly.  Occasionally  magneti-polar. 

Comp.— Platinum  combined  with  iron,  iridium,  osmium,  and  other  metals.  The  amount 
of  iron  varies  from  4-20  p.  c. 

Pyr.,  etc. — Infusible.  Not  affected  by  borax  or  salt  of  phosphorus,  except  in  the  state  of 
fine  dust,  when  reactions  for  iron  and  copper  may  be  obtained.  Soluble  only  in  heated  nitro- 
hydrochloric  acid. 


202  DESCRIPTIVE   MINERALOGY. 

Diff. — Distinguished  by  its  malleability,  high  specific  gravity,  infusibility,  and  entire  insol- 
ubility in  the  ordinary  acids. 

Obs, — Platinum  was  first  found  in  pebbles  and  small  grains  in  the  alluvial  deposits  of  the 
river  Pinto,  in  the  district  of  Choco,  near  Popayan,  in  South  America,  where  it  received  its 
name  platina,,  from  plata,  silver.  In  the  province  of  Antioquia,  in  Brazil,  it  has  been  found 
in  auriferous  regions  in  syenite  (Boussingault). 

In  Russia,  it  occurs  at  Nischne  Tagilsk,  and  Goroblagodat,  in  the  Ural,  in  alluvial  material. 
Formerly  used  as  coins  by  the  Russians.  Russia  affords  annually  about  800  cwt.  of  platinum, 
which  is  nearly  ten  times  the  amount  from  Brazil,  Columbia,  St.  Domingo,  and  Borneo. 
Platinum  is  also  found  on  Borneo  ;  in  the  sands  of  the  Rhine ;  at  St.  Aray,  val  du  Drac ; 
county  of  Wicklow,  Ireland ;  on  the  river  Jocky,  St.  Domingo  ;  in  California,  but  not  abun- 
dant :  in  traces  with  gold  in  Rutherford  Co. ,  North  Carolina  ;  at  St.  Francois  Beauce,  etc. , 
Canada  East. 

PLATINIRIDIUM.  — Platinum  and  iridium  in  different  proportions.     Urals  ;  Brazil. 

PALLADIUM. 

Isometric.  In  minute  octahedrons,  Haid.  Mostly  in  grains,  sometimes 
composed  of  diverging  fibres. 

H.  =  4-5-5.  G.=ll-3-ll-8,  Wollaston.  Lustre  metallic.  Color  whitish 
steel-gray.  Opaque.  Ductile  and  malleable. 

Comp. — Palladium,  alloyed  with  a  little  platinum  and  iridium,  but  not  yet  analyzed. 

Obs. — Palladium  occurs  with  platinum,  in  Brazil,  where  quite  large  masses  of  the  metal 
are  sometimes  met  with  ;  also  reported  from  St.  Domingo,  and  the  Ural. 

Palladium  has  been  employed  for  balances  ;  also  for  the  divided  scales  of  delicate  apparatus, 
for  which  it  is  adapted,  because  of  its  not  blackening  from  sulphur  gases,  while  at  the  same 
time  it  is  nearly  as  white  as  silver. 

IRIDOSMINE.     Osmiridium. 

Hexagonal.  Rarely  in  hexagonal  prisms  with  replaced  basal  edges. 
Commonly  in  irregular  flattened  grains. 

H.=6-7.  G.  =  19-3-21-r2.  Lustre  metallic.  Color  tin-white,  and  light 
steel  gray.  Opaque.  Malleable  with  difficulty. 

Comp.,  Var  — Iridium  and  osmium  in  different  proportions.  Two  varieties  depending  on 
these  proportions  have  been  named  as  species,  but  they  are  isomorphous,  as  are  the  metals 
(G.  Rose).  Some  rhodium,  platinum,  ruthenium,  and  other  metals  are  usually  present. 

Var.  1.  Newjanskite,  Haid. ;  H.=7;  G.  =18 '8-19 '5.  In  flat  scales  ;  color  tin-white.  Over 
40  p.  c.  of  Iridium.  Probably  IrOs. 

2.  Sisserskite,  Haid.  In  flat  scales,  often  six-sided,  color  grayish -white,  steel-gray.  G.  — 
20-21  '2.  Not  over  30  p.  c  of  iridium.  One  kind  from  Nischne  Tagilsk  afforded  Berzelius 
IrOs4=Iridium  19'9.  osmium  801  =  100  ;  G.  =21118.  Another  corresponded  to  the  formula 
IrOs3. 

Pyr.,  etc.— At  a  high  temperature  the  sisserskite  gives  out  osmium,  but  undergoes  no 
further  change.  The  newjanskite  is  not  decomposed  and  does  not  give  an  osmium  odor  until 
fused  with  nitre. 

Diff. — Distinguished  from  platinum  by  its  superior  hardness. 

Obs. — Occurs  with  platinum  in  the  province  of  Choco  in  South  America  ;  in  the  Ural  moun- 
tains ;  in  Australia.  It  is  rather  abundant  in'  the  auriferous  beach -sands  of  northern  Cali- 
fornia, occurring  in  small  bright  lead-colored  scales,  sometimes  six-sided.  Also  traces  in  the 
gold-washings  on  the  rivers  du  Loup  and  des  Plantes,  Canada. 

MERCURY.    Quicksilver.     Gediegen  Quecksilber,  Germ. 

Isometric.     Occurs  in  small  fluid  globules  scattered  through  its  gangue. 
G, =13.568.     Lustre  metallic.     Color  tin- white.     Opaque. 


NATIVE    ELEMENTS.  203 

Comp. — Pure  mercury  (Hg) ;  with  sometimes  a  little  silver. 

Pyr.,  etc.— B.B.,  entirely  volatile.     Dissolves  readily  in  nitric  acid. 

Obs. — Mercury  in  the  metallic  state  is  a  rare  mineral ;  the  quicksilver  of  commerce  is  ob- 
tained mostly  from  cinnabar,  one  of  its  ores.  The  rocks  affording  the  metal  and  its  ores  are 
mostly  clay  shales  or  schists  of  different  geological  ages. 

Its  most  important  mines  are  those  of  Idria  in  Carniola,  and  Almaden  in  Spain.  It  is 
found  in  small  quantities  in  Carinthia,  Hungary,  Peru,  and  other  countries ;  in  California, 
especially  in  the  Pioneer  mine,  in  the  Napa  Valley. 


,;.  AMALGAM, 

Isometric.  The  dodecahedron  a  common  form,  also  the  cube  and  octa- 
hedron in  combination  (see  f.  40,  41,  etc.,  p.  15).  Cleavage  :  dodecahedral 
in  traces.  Also  massive. 

H.=3-3'5.  G.=13.75-14.  Color  and  streak  silver-white.  Opaque. 
Fracture  conchoidal,  uneven.  Brittle,  and  giving  a  grating  noise  when 
cut  with  a  knife. 

Comp. — Both  Ag  Hg  (  —  Silver  35*1,  mercury,  64*9),  and  Ag2Hg3  (= Silver  26 '5,  and  mer- 
cury, 73  '5),  are  here  included. 

Pyr.,  etc, — B.B.,  on  charcoal  the  mercury  volatilizes  and  a  globule  of  silver  is  left.  In  the 
closed  tube  the  mercury  sublimes  and  condenses  on  the  cold  part  of  the  tube  in  minute  glo- 
bules. Dissolves  in  nitric  acid. 

Obs. — From  the  Palatinate  at  Moschellandsberg.  Also  reported  from  Rosenau  in  Hungary, 
Sala  in  Sweden,  Allemont  in  Dauphine,  Almaden  in  Spain. 

ARQUERITE. — Composition  Ag,2Hg=silver  86 '6,  mercury,  13'4=100.  Chili.  KONGS- 
BERGITE,  Ag18Hg  (?)  Kongsberg,  Norway. 


COPPER. 

Isometric.  Cleavage  none.  Twins :  twinning-plane  octahedral,  very 
common.  Often  filiform  and  arborescent ;  the  latter  with  the  branches 
passing  off  usually  at  60°,  the  supplement  of  the  dodecahedral  angle.  Also 
massive. 

II. =2-5-3.  Gr.=8'83S,  Whitney.  Lustre  metallic.  Color  copper-red. 
Streak  metallic  shining.  Ductile  and  malleable.  Fracture  hackly. 

Comp — Pure  copper,  but  often  containing  some  silver,  bismuth,  etc. 

Pyr,,  etc. — B.B.,  fuses  readily  ;  on  cooling,  becomes  covered  with  a  coating  of  black  oxide. 
Dissolves  readily  in  nitric  acid,  giving  off  red  nitrous  fumes,  and  producing  a  deep  azure-blue 
solution  upon  the  addition  of  ammonia. 

Obs.— Copper  occurs  hi  beds  and  veins  accompanying  its  various  ores,  and  is  most  abundant 
in  the  vicinity  of  dikes  of  igneous  rocks.  It  is  sometimes  found  in  loose  masses  imbedded  in 
the  soil. 

Found  at  Turinsk,  in  the  Urals,  in  fine  crystals.  Common  in  Cornwall.  In  Brazil,  Chili, 
Bolivia,  and  Peru.  At  Walleroo,  Australia. 

This  metal  has  been  found  native  throughout  the  red  sandstone  (Triassico- Jurassic)  region 
of  the  eastern  United  States,  in  Massachusetts,  Connecticut,  and  more  abundantly  in  New- 
Jersey,  where  it  has  been  met  with  sometimes  in  fine  crystalline  masses.  No  known  locality 
exceeds  in  the  abundance  of  native  copper  the  Lake  Superior  copper  region,  near  Keweenaw 
Point,  where  it  exists  in  veins  that  intersect  the  trap  and  sandstone,  m  d  where  masses  of 
immense  size  have  been  obtained.  It  is  associated  with  prehnite,  d  itolite,  analcite,  laumon- 
tite,  pectolite,  epidote,  chlorite,  wollastonite,  and  sometimes  coats  amygdules  of  calcite, 
etc.,  in  amygdaloid.  Native  copper  occurs  sparingly  in  California.  Also  on  the  G-ila  river 
in  Arizona ;  in  large  drift  masses  in  Alaska. 


204:  DESCRIPTIVE   MINERALOGY. 


IRON. 

Isometric.     Cleavage  octahedral. 

H.=4-5.  G.=7'3-7'8.  Lustre  metallic.  Color  iron-gray.  Streak  shin- 
ing. Fracture  hackly.  Malleable.  Acts  strongly  on  the  magnet. 

Obs, — The  occurrence  of  masses  of  native  iron  of  terrestrial  origin  has  been  several  times 
reported,  but  it  is  not  yet  placed  beyond  doubt.  The  presence  of  metallic  iron  in  grains  in 
basaltic  rocks  has  been  proved  by  several  observers.  It  has  also  been  noticed  in  other  related 
rocks.  The  so-called  meteoric  iron  of  Ovifak,  Greenland,  found  imbedded  in  basalt,  is  con- 
sidered by  some  authors  to  be  terrestrial. 

Meteoric  iron  usually  contains  1  to  20  per  cent,  of  nickel,  besides  a  small  percentage  of 
other  metals,  as  cobalt,  manganese,  tin,  copper,  chromium  ;  also  phosphorus  common  as  a 
phosphuret  (schreibersite),  sulphur  in  sulphurets,  carbon  in  some  instances,  chlorine.  Among 
large  iron  meteorites,  the  G-ibbs  meteorite,  in  the  Yale  College  cabinet,  weighs  1,635  Ibs.  ;  it 
was  brought  from  Red  River.  The  Tucson  meteorite,  now  in  the  Smithsonian  Institution, 
weighs  1,400  Ibs.  ;  it  was  originally  from  Sonora.  It  is  ring-shaped,  and  is  49  inches  in  its 
greatest  diameter.  Still  more  remarkable  masses  exist  in  northern  Mexico  ;  also  in  South 
America ;  one  was  discovered  by  Don  Rubin  de  Celis  in  the  district  of  Chaco-G-ualamba, 
whose  weight  was  estimated  at  32,000  Ibs.  The  Siberian  meteorite,  discovered  by  Pallas, 
weighed  originally  1,600  Ibs.  and  contained  imbedded  crystals  of  chrysolite.  Smaller  masses 
are  quite  common. 

ZINC. — Native  zinc  has  been  reported  to  occur  in  Australia;  and  more  recently  Mr.  W. 
D.  Marks  reports  its  discovery  in  Tennessee,  under  circumstances  not  altogether  free  from 
doubt. 

LEAD. — Native  lead  occurs  very  sparingly.  It  has  been  found  in  the  Urals,  in  Spain, 
Ireland,  etc.  Dr.  Genth  speaks  of  its  discovery  in  the  bed  rock  of  the  gold  placers  at  Camp 
Creek,  Montana. 

TIN  is  probably  only  an  artificial  product. 


ARSENIC. 

Ehombohedral.  BMt  =  85°  41',  O  A  R  =  122°  9',  c  =  1-3779,  Miller. 
Cleavage  :  basal,  imperfect.  Often  granular  massive  ;  sometimes  reticu- 
lated, reniform,  and  stalactitic.  Structure  rarely  columnar. 

H.=3'5.  G.=5'93.  Lustre  nearly  metallic.  Color  and  streak  tin-white, 
tarnishing  soon  to  dark-gray.  Fracture  uneven  and  line  granular. 

Comp. — Arsenic,  often  with  some  antimony,  and  traces  of  iron,  silver,  gold,  or  bismuth. 

Pyr. — B.B.,  on  charcoal  volatilizes  without  fusing,  coats  the  coal  with  white  arsenous  oxide, 
and  affords  the  odor  of  garlic  ;  the  coating  treated  in  R.F.  volatilizes,  tinging  the  flame  blue. 

Obs. — Native  arsenic  commonly  occurs  in  veins  in  crystalline  rocks  and  the  older  schists, 
and  is  often  acLompanied  by  ores  of  antimony,  red  silver  ore,  realgar,  sphalerite,  and  other 
metallic  minerals. 

The  silver  mines  of  Saxony  afford  this  metal  in  considerable  quantities  ;  also  Bohemia,  the 
Harz.  Transylvania,  Hungary,  Norway,  -  Siberia  ;  occurs  at  Chanarcillo,  and  elsewhere  in 
Chili;  and  at  the  mines  of  San  Augustin,  Mexico.  In  the  United  States  it  has  been 
observed  at  Haverhill  and  Jackson,  N.  H.,  at  Greenwood,  Me. 


ANTIMONY. 

Ehombohedral.  72  A  .#  =  87°  35 ',  Eose  ;  O  A  R  =  123°  32' ;  I  =  1-3068. 
2  A  2  =  89°  25'.  Cleavage  :  basal,  highly  perfect ;— \  distinct.  Generally 
massive,  lamellar ;  sometimes  botryoidal  or  reniform  with  a  granular  texture. 


NATIVE   ELEMENTS.  205 

H.=3-3-5.  G-.=6-64:6-6-72.  Lustre  metallic.  Color  and  streak  tin- 
white.  Very  brittle. 

Comp, — Antimony,  containing  sometimes  silver,  iron,  or  arsenic. 

Pyr,— B.B.,  on  charcoal  fuses,  gives  a  white  coating  in  both  O.  and  R.F.  ;  if  the  blowing 
be  intermitted,  the  globule  continues  to  glow,  giving  off  white  fumes,  until  it  is  finally  crusted 
over  with  prismatic  crystals  of  antimonous  oxide.  The  white  coating  tinges  the  R.F.  bluish- 
green.  Crystallizes  readily  from  fusion. 

Occurs  near  Sahl  in  Sweden ;  at  Andreasberg  in  the  Harz ;  at  Przibram ;  at  Allemont  in 
Dauphiny  ;  in  Mexico  ;  Chili ;  Borneo ;  at  South  Ham,  Canada  ;  at  Warren,  N.  J. ,  rare  ;  at 
Prince  William  antimony  mine,  N,  Brunswick,  rare.  i 

ALLEMONTITE. — Arsenical  antimony,  SbAs3.  Color  tin- white  or  reddish-gray.  Occurs  at 
Allemont ;  in  Bohemia  ;  the  Harz. 


BISMUTH.    Gediegen  Wismuth,  Germ. 

Hexagonal.  Rl\R  =  %T  40',  GK  Kose  ;  O  A  E  =  123°  36' ;  c  -  1-3035. 
Cleavage  :  basal,  perfect ;  2,  —2,  less  so.  Also  in  reticulated  and  arbores- 
cent shapes  ;  foliated  and  granular. 

H.=2-2-5.  G-. =9'727.  Lustre  metallic.  Streak  and  color  silver-white, 
with  a  reddish  hue  ;  subject  to  tarnish.  Opaque.  Fracture  not  observable. 
Sectile.  Brittle  when  cold,  but  when  heated  somewhat  malleable. 

Comp.,  Var. — Pure  bismuth,  with  occasional  traces  of  arsenic,  sulphur,  tellurium. 

Pyr.,  etc. — B.B.,  on  charcoal  fuses  and  entirely  volatilizes,  giving  a  coating  orange-yellow 
while  hot,  and  lemon-yellow  on  cooling.  Dissolves  in  nitric  acid  ;  subsequent  dilution  causes 
a  white  precipitate.  Crystallizes  readily  from  fusion. 

Diff  — Distinguished  by  its  reddish  color,  and  high  specific  gravity,  from  the  other  brittle 
metals. 

Obs  — Bismuth  occurs  in  veins  in  gneiss  and  other  crystalline  rocks  and  clay  slate,  accom- 
panying various  ores  of  silver,  cobalt,  lead,  and  zinc.  Abundant  at  the  silver  and  cobalt 
mines  of  Saxony  and  Bohemia  ;  also  found  in  Norway,  and  at  Fahlun  in  Sweden.  At  Wheal 
Sparnon,  and  elsewhere  in  Cornwall,  and  at  Carrack  Fell  in  Cumberland  ;  at  the  Atlas  mine, 
Devonshire ;  at  Meymac,  Correze  ;  at  San  Antonio,  Chili  ;  Mt.  Illampa  (Sorata),  in  Bolivia ; 
in  Victoria. 

At  Lane's  mine  in  Monroe,  and  near  Seymour,  Conn.,  in  quartz  ;  occurs  also  at  Brewer's 
mine,  Chesterfield  district,  South  Carolina  ;  in  Colorado. 


TELLURIUM. 

Hexagonal,  R  A  R  =  86°  57',  G.  Eose  ;  0  A  R  =  123°  4',  c  =  1-3302. 
In  six-sided  prisms,  with  basal  edges  replaced.  Cleavage  :  lateral  perfect, 
basal  imperfect.  Commonly  massive  and  granular. 

II. =2-2 -5.  G.^6-1-6'3."  Lustre  metallic.  Color  and  streak  tin- white. 
Brittle. 

Comp. — According  to  Klaproth,  Tellurium  92 '55,  iron  7-20.  and  gold  0'25. 

Pyr — In  the  open  tube  fuses,  giving  a  white  sublimate  of  tellurous  oxide,  which  B.B, 
fuses  to  colorless  transparent  drops.  On  charcoal  fuses,  volatilizes  almost  entirely,  tinges  the 
flame  green,  and  gives  a  white  coating  of  tellurous  oxide. 

Obs. — Native  tellurium  occurs  in  Transylvania  (whence  the  name  Sylvanite),  gold ;  also  at 
the  Red  Cloud  mine,  near  Gold  Hill,  Boulder  Co.,  Colorado. 


206 


DESCRIPTIVE   MINERALOGY. 


NATIVE  SULPHUR. 


Orthorhombic.     /A  7  =  101°  46',  0A14  = 


c  :  5  :  &  =  2-344  : 


,1-23  :  1.     O  A  l-£  =  117°  41' ;   O  A 1  =  108°  19'. 

Cleavage :  /,  and  1,  imperfect.  Twins, 
composition -face,  /,  sometimes  producing  cruci- 
form crystals.  Also  massive,  sometimes  con- 
sisting of  concentric  coats. 

H.=l-5-2-5.  G. =2-072,  of  crystals  from 
Spain.  Lustre  resinous.  Streak  sulphur-yel- 
low, sometimes  reddish  or  greenish.  Trans- 
parent— subtranslucent.  Fracture  conchoidal, 
more  or  less  perfect.  Sectile. 

Comp. — Pure  sulphur ;  but  often  contaminated  with  clay  or  bitumen. 

Pyr.,  etc. — Burns  at  a  low  temperature  with  a  bluish  tiame,  with  the  strong  odor  of  sul- 
phurous oxide.  Becomes  resinously  electrified  by  friction.  Insoluble  in  water,  and  not 
acted  on  by  the  acids. 

Obs, — Sulphur  is  dimorphous,  the  crystals  being  monoclinic  when  formed  at  a  moderately 
high  temperature  (125°  C.,  according  to  Frankenheim). 

The  great  repositories  of  sulphur  are  either  beds  of  gypsum  and  the  associate  rocks,  or  the 
regions  of  active  and  extinct  volcanoes.  In  the  valley  of  Noto  and  Mazarro,  in  Sicily ;  at 
Conil,  near  Cadiz,  in  Spain  ;  Bex,  in  Switzerland  ;  Cracow,  in. Poland,  it  occurs  in  the  former 
situation;  also  Bologna,  Italy.  Sicily  and  the  neighboring  volcanic  isles;  the  Solfatara,  near 
Naples  ;  the  volcanoes  of  the  Pacific  ocean,  etc.,  are  localities  of  the  latter  kind.  Abundant 
in  the  Chilian  Andes. 

Sulphur  is  found  near  the  sulphur  springs  of  New  York,  Virginia,  etc. ,  sparingly  ;  in  many 
coal  deposits  and  elsewhere,  where  pyrite  is  undergoing  decomposition  ;  at  the  hot  springs 
and  geysers  of  the  Yellowstone  park  ;  in  California,  at  the  geysers  of  Napa  valley,  Sonoma 
Co.  ;  in  Santa  Barbara  in  good  crystals  ;  near  Clear  lake,  Lake  Co.  ;  in  Nevada,  in  Humboldt 
Co.,  in  large  beds  ;  Nye  and  Esmeralda  Cos.,  etc. 

The  sulphur  mines  of  Sicily,  the  crater  of  Vulcano,  the  Solfatara  near  Naples,  and  the  beds 
of  California,  afford  large  quantities  of  sulphur  for  commerce. 


DIAMOND. 

Isometric.     Often  tetrahedral  in  planes,  1,  2,  and 
418  419 


Usually  with 
420 


curved  faces,  as  in  f.  419  (3-f ) ;  f .  420  is  a  distorted  form.     Cleavage  : 
octahedral,  highly  perfect.     Twins:  twinning-plane,  octahedral;  f.  418,  is 


NATIVE   ELEMENTS.  207 

an  elliptic  twin  of  f.  419,  the  middle  portion  between  two  opposite  sets  of 
six  planes  being  wanting.     Rarely  massive. 

H.=10.  G.= 3.5295,  Thompson.  Lustre  brilliant  adamantine.  Color 
white  or  colorless  :  occasionally  tinged  yellow,  red,  orange,  green,  blue, 
brown,  sometimes  black.  Transparent ;  translucent  when  dark  colored. 
Fracture  conchoid al.  Index  of  refraction  2-4.  Exhibits  vitreous  electricity 
when  rubbed. 

Comp. — Pure  carbon,  isometric  in  crystallization. 

Var. — ] .  Ordinary,  or  crystallized.  The  crystals  often  contain  numerous  microscopic  cavi- 
ties, as  detected  by  Brewster ;  and  around  these  cavities  the  diamond  shows  evidence,  by 
polarized  light,  of'  compression,  as  if  from  pressure  in  the  included  gas  when  the  diamond 
was  crystallized.  The  coarse  varieties,  which  are  unfit,  in  consequence  of  imperfections,  for 
use  in  jeweJry,  are  called  bortj  they  are  sold  to  the  trade  for  cutting  purposes. 

2.  Massive.    In  black  pebbles  or  masses,  called  carbonado,  occasionally  1,000  carats  in  weight. 
H  =10  ;  G.  =3 -012-3 -410.     Consists  of  pure  carbon,  excepting  0'27  to  2*07  p.  c.  (Brazil). 

3.  Anthracitic.     Like  anthracite,  but  hard  enough  to  scratch  even  the  diamond.     In  glo- 
bules or  mammillary  masses,  consisting  partly  of  concentric  layers  ;  fragile  ;  G.=1'66;  com- 
position, Carbon  97,  hydrogen  0'5,  oxygen  1/5.     Cut  in  facets  and  polished,  it  refracts  and 
disperses  light,  with  the  white  lustre  peculiar  to  the  diamond.     Locality  unknown,  but  sup- 
posed to  come  from  Brazil. 

Pyr.,  etc.— Burns,  and  is  wholly  consumed  at  a  high  temperature,  producing  carbonic 
dioxide.  It  is  not  acted  on  by  acids  or  alkalies. 

Diff. — Distinguished  by  its  extreme  hardness,  brilliancy  of  reflection,  and  adamantine  lustre. 

Obs. — The  diamond  often  occurs  in  regions  that  afford  a  laminated  granular  quartz  rock, 
called  itacolumyte,  which  pertains  to  the  talcose  series,  and  which  in  thin  slabs  is  more  or 
less  flexible.  This  rock  is  found  at  the  mines  of  Brazil  and  the  Urals ;  and  also  in  Georgia 
and  North  Carolina,  where  a  few  diamonds  have  been  found.  It  has  also  been  detected  in  a 
species  of  conglomerate,  composed  of  rounded  siliceous  pebbles,  quartz,  chalcedony,  etc., 
cemented  by  a  kind  of  ferruginous  clay.  Diamonds  are  usually,  however,  washed  out  from 
the  soil.  The  Ural  diamonds  occur  in  the  detritus  along  the  Adolfskoi  rivulet,  where  worked 
for  gold,  and  also  at  other  places.  In  India  the  diamond  is  met  with  at  Purteal,  between 
Hyderabad  and  Masulipatam,  where  the  famous  Kohinoor  was  found.  The  locality  on  Borneo 
is  at  Pontiana,  on  the  west  side  of  the  Ratoos  mountain.  Also  found  in  Australia. 

The  diamond  region  of  South  Africa,  discovered  in  1807,  is  the  most  productive  at  the 
present  time.  The  diamonds  occur  in  the  gravel  of  the  Vaal  river,  from  Potchefstrom,  cap- 
ital of  the  Transvaal  Republic,  down  its  whole  course  to  its  junction  with  the  Orange  river, 
and  thence  along  ths  latter  stream  for  a  distance  of  60  miles.  In  addition  to  this  the  dia- 
monds are  found  also  in  the  Orange  River  Republic,  in  isolated  fields  or  Pans,  of  which  Du 
Toit's  Pan  is  the  most  famous.  The  number  of  diamonds  which  have  been  found  at  the  Cape 
is  very  large,  and  some  of  them  are  of  considerable  size.  It  has  been  estimated  that  the  value 
of  those  obtained  from  March,  1867,  to  November,  1875,  exceeded  sixty  millions  of  dollars. 
As  a  consequence  of  this  production  the  market  value  of  the  stones  has  been  much  dimin- 
ished. 

In  the  United  States  a  few  crystals  have  been  met  with  in  Rutherford  Co.,  N.  C. ,  and  Hall 
Co.,  Ga. ;  they  occur  also  at  Portis  mine,  Franklin  Co.,  N.  C.  (Genth) ;  one  handsome  one, 
over  £  in.  in  diameter,  in  the  village  of  Manchester,  opposite  Richmond,  Va.  In  California, 
at  Cherokee  ravine,  in  Butte  Co.  ;  also  in  N.  San  Juan,  Nevada  Co.,  and  elsewhere  in  the 
gold  washings.  Reported  from  Idaho,  and  with  platinum  of  Oregon. 

The  largest  diamond  of  which  we  have  any  knowledge  is  mentioned  by  Tavernier  as  in 
possession  of  the  Great  Mogul.  It  weighed  originally  900  carats,  or  2769  3  grains,  but  was 
reduced  by  cutting  to  861  grains.  It  has  the  form  and  size  of  half  a  hen's  egg.  It  was  found 
in  1550,  in  the  mine  of  Colone.  The  Pitt  or  Regent  diamond  weighs  but  136 -25  carats,  or 
419£  grains  ;  but  is  of  unblemished  transparency  and  color.  It  is  cut  in  the  form  of  a  bril- 
liant, and  its  value  is  estimated  at  £125,000.  The  Kohinoor  measured,  on  its  arrival  in  Eng- 
land, about  If  inches  in  its  greatest  diameter,  over  £  of  an  inch  in  thickness,  and  weighed 
186-t/r  carats,  and  was  cut  with  many  facets.  It  has  since  been  recut,  and  reduced  to  a  dia- 
meter of  l-|7:g  by  If  nearly,  and  thus  diminished  over  one-third  in  weight.  It  is  supposed  by 
Mr.  Tennant  to  have  been  originally  a  dodecahedron,  and  he  suggests  that  the  great  Russian 
diamond  and  another  large  slab  weighing  130  carats  were  actu-illy  cut  from  the  original  dode- 
cahedron. Tavernier  gives  the  original  weight  at  787£  carats.  The  Rajah  of  Mattan  has  in 
his  possession  a  diamond  from  Borneo,  weighing  367  carats.  The  mines  of  Brazil  were  not 
known  to  afford  diamonds  till  the  commencement  of  the  eighteenth  century. 


208  DESCEIPTIVE   MINERALOGY. 


GRAPHITE.    Plumbago. 

Hexagonal.  In  flat  six-sided  tables.  The  basal  planes  (0)  are  often 
striated  parallel  to  the  alternate  edges.  Cleavage  :  basal,  perfect.  Com- 
monly in  imbedded,  foliated,  or  granular  masses.  Rarely  in  globular  con- 
cretions, radiated  in  structure. 

H.— 1-2.  G.=2-09-2-229.  Lustre  metallic.  Streak  black  and  shining. 
Color  iron-black — dark  steel-gray.  Opaque.  Sectile  ;  soils  paper.  Thin 
laminee  flexible.  Feel  greasy. 

Var. — (a}  Foliated ;  (5)  columnar,  and  sometimes  radiated  ;  (c)  scaly,  massive,  and  slaty  ; 
(d)  granular  massive ;  (e)  earthy,  amorphous,  without  metallic  lustre  except  in  the  streak  ; 
(/)  in  radiated  concretions. 

Comp. — Pure  carbon,  with  often  a  little  iron  sesquioxide  mechanically  mixed. 

Pyr.,  etc. — At  a  high  temperature  it  burns  without  flame  or  smoke,  leaving  usually  some 
red  oxide  of  iron.  B.B.  infusible ;  fused  with  nitre  in  a  platinum  spoon,  deflagrates,  con- 
verting the  reagent  into  potassium  carbonate,  which  effervesces  with  acids.  Unaltered  by 
acids. 

Diff. — See  molybdenite,  p.  211. 

Obs, — Graphite  occurs  in  beds  and  imbedded  masses,  laminae,  or  scales,  in  granite,  gneiss, 
mica  schists,  crystalline  limestone.  It  is  in  some  places  a  result  of  the  alteration  by  heat  of 
the  coal  of  the  coal  formation.  Sometimes  met  with  in  greenstone.  It  is  a  common  furnace 
product. 

Occurs  at  Borrowdale  in  Cumberland  ;  in  Glenstrathfarrar  in  Invernesshire  ;  at  Arendal  in 
Norway;  in  the  Urals,  Siberia,  Finland;  in  various  parts  of  Austria;  Prussia;  France. 
Large  quantities  are  brought  from  the  East  Indies. 

In  the  United  States,  the  mines  of  Sturbridge,  Mass.,  of  Ticonderoga  and  Fishkill,  N.  Y,, 
of  Brandon,  Vt.,  and  of  Wake,  N.  C.,  are  worked;  and  that  of  Ashford,  Conn.,  formerly 
afforded  a  large  amount  of  graphite.  It  occurs  sparingly  at  many  other  localities. 

The  name  black  lead,  applied  to  this  species,  is  inappropriate,  as  it  contains  no  lead.  The 
name  graphite,  of  Werner,  is  derived  from  ypdtjxa,  to  write. 

Nordenskiold  makes  the  graphite  of  Ersby  and  Storgard  monoclinic. 


II.  SULPHIDES,  TELLURIDES,  SELENIDES,  ARSEN- 
IDES, BISMUTHIDES. 


1.  BINARY  COMPOUNDS.— SULPHIDES  AND  TELLUKIDES  OF  THE  METALS 
OF  THE  SULPHUR  AND  AKSENIC  GROUPS. 


REALGAR, 

Monoclinic.     C  =  66°  5',  /  A I  =  74°  26',  Marignac,  Scacchi,  0  A 14  = 
138°  21' ;  c:b:d  =  0-6755  :  0-6943  : 1.    Habit  pris- 
matic.    Cleavage  :  i-l,   0  rather  perfect ;  I,  i-i  in 
traces.     Also  granular,  coarse  or  fine  ;  compact. 

H.= 1-5-2.  G.  =  3'4-3-6.  Lustre  resinous.  Color 
aurora-red  or  orange-yellow.  Streak  varying  from 
orange-red  to  aurora-red.  Transparent — translu- 
cent. Fracture  conchoidal,  uneven. 

Comp,— AsS  —  Sulphur  29.9,  arsenic  70-1=100. 

Pyr,,  etc, — In  the  closed  tube  melts,  volatilizes,  and  gives  a 
transparent  red  sublimate  ;  in  the  open  tube,  sulphurous  fumes, 
and  a  white  crystalline  sublimate  of  arsenous  oxide.  B.B.  on 

charcoal  burns  with  a  blue  flame,  emitting  arsenical  and  sulphurous  odors.     Soluble  in  caustic 
alkalies. 

Obs. — Occurs  with  ores  of  silver  and  lead,  in  Upper  Hungary  ;  in  Transylvania  ;  at  Joachims- 
thai  ;  Schneeberg ;  Andreasberg ;  in  the  Binnenthal,  Switzerland,  in  dolomite  ;  at  Wiesloch 
in  Baden  ;  near  Julamerk  in  Koordistan  ;  in  Vesuvian  lavas,  in  minute  crystals. 


ORPIMENT. 

Orthorhombic.  7  A  7  =  100°  40',  O  A  I-i  =  126°  30',  Mohs.  c:t>:d  = 
1*3511  :  1-2059  :  1.  Cleavage  :  i-i  highly  perfect,  i-l  in  traces,  i-%  longi- 
tudinally striated.  Also,  massive,  foliated,  or  columnar ;  sometimes  reni- 
form. 

II.  =  1-5-2.  GL i=3-48,  Haidinger.  Lustre  pearly  upon  the  faces  of  per- 
fect cleavage  ;  elsewhere  resinous.  Color  several  shades  of  lemon-yellow. 
Streak  yellow,  commonly  a  little  paler  than  the  color.  Subtransparent — 
subtranslucent.  Sub-sectile.  Thin  laminae  obtained  by  cleavage  flexible 
but  not  elastic. 


Comp,— As2S3  =  Sulphur  39,  arsenic  61—100. 

Pyr.,  etc. — In  the  closed  tube,  fuses,  volatilizes,  and  gives  a  dark  yellow  sublimate ;  other 
reactions  the  same  as  under  realgar.  Dissolves  in  nitro-hydrochloric  acid  and  caustic  alkalies. 

Obs  — Orpiment  in  small  crystals  is  imbedded  in  clay  at  Tajowa,  in  Upper  Hungary.  It  is 
usually  in  foliated  and  fibrous  masses,  and  in  this  form  is  found  at  Kapnik,  at  Moldawa,  and 
at  Felsobanya  ;  at  Hall  in  the  Tyrol  it  is  found  in  gypsum  ;  at  St.  Gothard  in  dolomite  ;  at 

14 


210 


DESCRIPTIVE   MINERALOGY. 


the  Solfatara  near  Naples.  Near  Julamerk  in  Koordistan.  Occurs  also  at  Acobambillo,  Peru. 
Small  traces  are  met  with  in  Edenville,  Orange  Co. ,  N.  Y. 

The  name  orpiment  is  a  corruption  of  its  Latin  name  auripigmentum,  ' '  golden  paint" 
which  was  given  in  allusion  to  the  color,  and  also  because  the  substance  was  supposed  to  con- 
tain gold. 

DIMORPHITE  of  Scacchi  may  be,  according  to  Kenngott,  a  variety  of  orpiment. 


STIBNITE,    Antimonite.  Gray  Antimony.  Antimony  Glance.  Antimonglanz,  Germ, 

Orthorhorabic.  /A  7  =  90°  54',  O  A  14  =  134°  16',  Krenner ;  c  :  I  :  &  = 

1-0259  :  1-0158  :  1.  O  A  1  =  124° 
422  423  45' ;  O  A  \-l  =  134°  42J'. 

Lateral  planes  deeply  striated 
longitudinally.  Cleavage  :  i-i  highly 
perfect.  Often  columnar,  coarse  or 
fine  ;  also  granular  to  impalpable. 

H.=2.  *~G.= 4-516,  Haiiy.  Lustre 
metallic.  Color  and  streak  lead- 
gray,  inclining  to  steel-gray :  sub- 
ject to  blackish  tarnish,  sometimes 
iridescent.  Fracture  small  sub-con- 
choidal.  Sectile.  Thin  laminae  a 
little  flexible. 


Comp. — Sb2S  3  =  Sulphur  28 '2,  antimony  71  '8=100. 

Pyr.,  etc, — In  the  open  tube  sulphurous  and  antimonous  fumes,  the  latter  condensing  as  a 
white  sublimate  which  B.B.  is  non-volatile.  On  charcoal  fuses,  spreads  out,  gives  sulphurous 
and  antimonous  fumes,  coats  the  coal  white;  this  coating  treated  in  R.F.  tinges  the  flame 
greenish-blue.  Fus.  —  1.  When  pure  perfectly  soluble  in  hydrochloric  acid. 

Diff — Distinguished  by  its  perfect  cleavage  ;  also  by  its  extreme  fusibility  and  other  blow- 
pipe characters. 

Obs. — Occurs  with  spathic  iron  in  beds,  but  generally  in  veins.  Often  associated  with 
blende,  barite,  and  quartz. 

Met  with  in  veins  at  Wolfsberg,  in  the  Harz  ;  at  Briiunsdorf,  near  Freiberg ;  at  Przibram  ; 
in  Hungary;  at  Pereta,  in  Tuscany;  in  the  Urals;  in  Dumfriesshire;  in  Cornwall.  Also 
found  in  different  Mexican  mines.  Also  abundant  in  Borneo. 

In  the  United  States,  it  occurs  sparingly  at  Carmel,  Me.  ;  at  Cornish  and  Lyme,  N.  H.  ; 
at  u  Soldier's  Delight,"  Md.  ;  in  the  Humboldt  mining  region  in  Nevada ;  also  in  the  mines 
of  Aurora,  Esmeralda  Co.,  Nevada.  Also  found  in  New  Brunswick,  20  m.  from  Fredericton, 
S.  W.  side  of  St.  John  R. 

This  ore  affords  much  of  the  antimony  of  commerce.  The  crude  antimony  of  the  shops  is 
obtained  by  simple  fusion,  which  separates  the  accompanying  rock.  From  this  product  most 
of  the  pharmaceutical  preparations  of  antimony  are  made,  and  the  pure  metal  extracted. 

LIVINGSTONITE  (Barcena). — Resembles  stibnite  in  physical  characters,  but  has  a  red 
streak,  and  contains,  besides  sulphur  and  antimony,  14  p.  c.  mercury.  Huitzuco,  State  of 
Guerrero,  Mexico. 


BISMUTHINITE.     Bismuth  Glance.     Wismuthglanz,  Germ. 


Orthorhombic.     If\I  =  91°  30',  Haidinger. 
perfect ;  macrodiagonal  less  so  ;  basal  perfect. 


Cleavage :  brachydiagonal 
In  acicnlar  crystals.     Also 
massive,  with  a  foliated  or  fibrous  structure. 

EL  =  2.  G.  =  6-4-6-459  ;  7'2;  7'1 6,  Bolivia,  Forbes.  Lustre  metallic. 
Streak  and  color  lead-gray,  inclining  to  tin-white,  with  a  yellowish  or  irides- 
cent tarnish.  Opaque. 


SULPHIDES,    TELLHRIDES,    SELENIDES,   ETC.  211 

Comp. — Bi2S  3  =  Sulphur  18*75,  bismuth  81 '25=100  ;  isomorphous  with  stibnite. 

Pyr.,  etc. — In  the  open  tube  sulphurous  fumes,  and  a  white  sublimate  which  B.B.  fuses 
into  drops,  brown  while  hot  and  opaque  yellow  on  cooling1.  On  charcoal  at  first  gives  sul- 
phurous fumes,  then  fuses  with  spirting,  and  coats  the  coal  with  yellow  bismuth  oxide. 
Fus.  =1.  Dissolves  readily  in  hot  nitric  acid,  and  a  white  precipitate  falls  on  diluting  with 
water. 

Obs. — Found  at  Brandy  Gill,  Carrook  Fells,  in  Cumberland  ;  near  Redruth ;  at  Botallack 
near  Land's  End ;  at  Herland  Mine,  G-wennap  ;  with  childrenite,  near  Callington  ;  in  Saxony  ; 
at  Riddarhyttan,  Sweden  ;  near  Sorata,  Bolivia.  Occurs  in  Rowan  Co.,  N.  C. ,  at  the  Barn- 
hardt  vein  ;  at  Haddam,  Ct.  ;  Beaver  Co.,  Utah. 

GUANA JUATITE  ;  Frenzelite.  Fernandez,  1873  ;  Castillo,  1873  ;  Frenzel,  1874. — A  bismuth 
selenide,  Bi2Se3  ;  sometimes  with  part  of  the  selenium  replaced  by  sulphur,  that  is,  Bi2(Se,S)3, 
with  Se  :  S=3  :  2,  which  requires  Selenium  23*8,  sulphur  0'5,  bismuth  69 '7 =100.  Isomor- 
phous with  stibnite  and  bismuthinite  (Schrauf).  Guanajuato,  Mexico.  SILAONITE  from 
Guanajuato  is  Bi3Se  (Fernandez). 


TETRADYMITE,     Tellurwismuth,  Germ. 

Hexagonal.  O  A  R  =  118°  38',  R  A  R  =  81°  2' ;  c=  1-5865.  Crystals 
often  tabular.  Cleavage  :  basal,  very  perfect.  Also  massive,  foliated,  or 
granular. 

II.  =  1-5- 2.  G.=7-2-7'9.  Lustre  metallic,  splendent.  Color  pale  steel- 
gray.  Not  very  sectile.  Laminae  flexible.  Soils  paper. 

Comp.,  Var. — Consists  of  bismuth  and  tellurium,  with  sometimes  sulphur  and  selenium. 
If  sulphur,  when  present,  replaces  part  of  the  tellurium,  the  analyses  for  the  most  part  afford 
the  general  formula  Bi2(Te,  S)3.  Var.  1. — Free  from  sulphur.  Bi2Te3  =  Tellurium  48-1, 
bismuth  51 '9;  G.  =7*868,  from  Dahlonega,  Jackson;  7 -642,  id.,  Balch.  2.  Sulphurous. 
Containing  4  or  5  p.  c.  sulphur.  S.  — 7'500,  crystals  from  Schubkau,  Wehrle. 

Pyr. — In  the  open  tube  a  white  sublimate  of  tellurous  oxide,  which  B.B.  fuses  to  colorless 
drops.  On  charcoal  fuses,  gives  white  fumes,  and  entirely  volatilizes  ;  tinges  the  R.F.  bluish- 
green  ;  coats  the  coal  at  first  white  (tellurous  oxide),  and  finally  orange-yellow  (bismuth 
oxide) ;  some  varieties  give  sulphurous  and  selenous  odors. 

Diff. — Distinguished  by  its  easy  fusibility  ;  tendency  to  foliation,  and  high  specific  gravity. 

Obs. — Occurs  at  Schubkau,  near  Schemnitz ;  at  Retzbanya  ;  Orawitza ;  at  Tellemark  in 
Norway ;  at  Bastnaes  mine,  near  Riddarhyttan,  Sweden. 

In  the  United  States,  associated  with  gold  ores,  in  Virginia  ;  in  North  Carolina,  Davidson 
Co. ,  etc.  Also  occurs  in  Georgia,  4  m.  E.  of  Dahlonega,  and  elsewhere  ;  Highland,  Montana 
T.  ;  Red  Cloud  mine,  Colorado,  rare ;  Montgomery  mine,  Arizona. 

JOSEITE. — A  bismuth  telluride,  in  which  half  the  tellurium  is  replaced  by  sulphur  and 
selenium  ;  Brazil. 

WEHRLITE.— Composition  probably  Bi(Te,  S).     G.=8'44.     Deutsch  Pilsen,  Hungary. 


MOLYBDENITE.    Molybdanglanz,  Germ. 

In  short  or  tabular  hexagonal  prisms.     Cleavage :  eminent,  parallel  to 
base  of  hexagonal  prisms.     Commonly  foliated,  massive,  or  in  scales:  also 


fine  granular. 


II.  =  1-1-5,  being  easily  impressed  by  the  nail.  G.=4-44r-4'8.  Lustre 
metallic.  Color  pure  lead-gray.  Streak  similar  to  color,  slightly  inclined 
to  green.  Opaque.  Laminae  very  flexible,  not  elastic.  Sectile,  and  almost 
malleable.  Bluish-gray  trace  on  paper. 


212  DESCRIPTIVE   MINERALOGY. 

Comp MoS2  =  Sulphur  41'0,  molybdenum  59-0=100. 

Pyr.,  etc. — In  the  open  tube  sulphurous  fumes.  B.B.  in  the  forceps  infusible,  imparts  a 
yellowish-green  color  to  the  flame  ;  on  charcoal  the  pulverized  mineral  gives  in  O.  F.  a  strong 
odor  of  sulphur,  and  coats  the  coal  with  crystals  of  molybdic  oxide,  which  appear  yellow 
while  hot,  and  white  on  cooling ;  near  the  assay  the  coating  is  copper-red,  and  if  the  white 
coating  be  touched  with  an  intermittent  R.F.,  it  assumes  a  beautiful  azure-blue  color. 
Decomposed  by  nitric  acid,  leaving  a  white  or  grayish  residue  (molybdic  oxide). 

Diff. — Distinguished  from  graphite  by  its  color  and  streak,  and  also  by  its  behavior  (yield- 
ing sulphur,  etc.)  before  the  blowpipe. 

Obs — Molybdenite  generally  occurs  imbedded  in,  or  disseminated  through,  granite,  gneiss, 
zircon-syenite,  granular  limestone,  and  other  crystalline  rocks.  Found  in  Sweden  •,  Norway ; 
Russia.  Also  in  Saxony  ;  in  Bohemia  ;  Rathausberg  in  Austria  ;  near  Miask,  Urals  ;  Chessy 
in  France  ;  Peru  ;  Brazil ;  Calbeck  Fells,  and  elsewhere  in  Cumberland  ;  several  of  the  Cornish 
mines;  in  Scotland  at  East  Tulloch,  etc. 

In  Maine,  at  Blue  Hill  Bay  and  Camdage  farm.  In  Conn.,  at  Haddam.  In  Vermont,  at 
Newport.  In  N.  Hampshire,  at  Westmoreland ;  at  Llandaff  ;  at  Franconia.  In  Mass.,  at 
Shutesbury  ;  at  Brimfield.  In  N.  York,  near  Warwick.  In  Penn.,  in  Chester,  on  Chester 
Creek  ;  near  Concord,  Cabarrus  Co.,  N.  C.  In  California,  at  Excelsior  gold  mine,  in  Excel- 
sior district.  In  Canada,  at  several  places. 


2.  BINAEY   COMPOUNDS.— SULPHIDES,  TELLURIDES,  ETC.,  OF  METALS 
OF  THE  GOLD,  IRON,  AND  TIN  GROUPS. 

A.  "BASIC  DIVISION. 

DYSCRASITE.     Antimonial  Silver.     Antimon-Silber,  Germ. 

Orthorhornbic,  /A  7  =  119°  59'  ;  O  A  14  130°  41' ;  c  :  I  :  a  =  1-1633: 
1-73 15  :  1 ;  O  A  1  —  126°  40' ;  0  A  14  =  146°  6'.  Cleavage  :  basal  distinct : 
14  also  distinct ;  /  imperfect.  Twins :  stellate  forms  and  hexagonal 
prisms.  Prismatic  planes  striated  vertically.  Also  massive,  granular ;  par- 
ticles of  various  sizes,  weakly  coherent. 

H. =3-5-4.  G.=9-44-9-82.  Lustre  metallic.  Color  and  streak  silver- 
white,  inclining  to  tin-white ;  sometimes  tarnished  yellow  or  blackish. 
Opaque.  Fracture  uneven. 

Comp.—Ag4Sb= Antimony  22,  silver  78=100.  Also  Ag6Sb= Antimony  15  '66,  silver  84'34, 
and  other  proportions. 

Pyr.,  etc. — B.  B.  on  charcoal  fuses  to  a  globule,  -coating  the  coal  with  white  antimonous 
oxide,  and  finally  giving  a  globule  of  almost  pure  silver.  Soluble  in  nitric  acid,  leaving  anti- 
monous oxide. 

Obs.— Occurs  near  Wolfach  in  Baden,  Wittichen  in  Suabia,  and  at  Andreasberg  ;  also  at 
Allemont  in  Daupbine,  Casalla  in  Spain,  and  in  Bolivia,  S.  A. 


DOMEYKITE.    Arsenikkupfer,  Germ. 

Heniform  and  botryoidal ;  also  massive  and  disseminated. 

H.= 3-3-5.  G.= 7-7*50,  Portage  Lake,  Genth.  Lustre  metallic  but  dull 
on  exposure.  Color  tin-white  to  steel-gray,  with  a  yellowish  to  pinchbeck- 
brown,  and,  afterward,  an  iridescent  tarnish.  Fracture  uneven. 


SULPHIDES,    TELLURIDES,    SELENIDES,    ETC.  213 

Comp. — Cu3 As = Arsenic  2S'3,  copper  71 '7=100. 

Pyr.,  etc. — In  the  open  tube  fuses  and  gives  a  white  crystalline  sublimate  of  arsenous 
oxide.  B.B.  on  charcoal  arsenical  fumes  and  a  malleable  metallic  globule,  which,  on  treat- 
ment with  soda,  gives  a  globule  of  pure  copper.  Not  dissolved  in  hydrochloric  acid,  but 
soluble  in  nitric  acid. 

Obs. — From  the  mines  of  Chili.  In  N.  America,  found  on  the  Sheldon  location,  Portage 
Lake ;  and  at  Michipicoten  Island,  in  L.  Superior. 

ALGODONITE. — Composition,  Cu6  As = Arsenic  16  "5,  copper  83'5.    Chili ;  also  Lake  Superior. 

WHITNEYITE.— Cu9As=: Arsenic  11*0,  copper  88 '4 =100.  Houghton,  Mich.,  also  Calif ornia, 
Arizona. 


B.  PHOTO  DIVISION. 

(a)  Galenite  Group.     Isometric ;    holohedral. 

ARG-ENTITE.     Silver  Glance.    Vitreous  Silver.     Silberglanz,  Germ. 

Isometric.  Cleavage  :  dodecahedral  in  traces.  Also  reticulated,  arbores- 
cent, and  filiform  ;  also  amorphous. 

H.=:  2-2-5.  G.= 7-196-7-365.  Lustre  metallic.  Streak  and  color  black- 
ish lead-gray  ;  streak  shining.  Opaque.  Fracture  small  sub-conchoidal, 
uneven.  Malleable. 

Comp.— Ag2S=: Sulphur  12'9,  silver  871=100. 

Pyr.,  etc. — In  the  open  tube  gives  off  sulphurous  oxide.  B.B.  on  charcoal  fuses  with  intu- 
mescence in  O.F.,  emitting  sulphurous  fumes,  and  yielding  a  globule  of  silver. 

Diff. — Distinguished  from  other  silver  ores  by  its  malleability. 

Obs — Found  in  the  Erzgebirge  ;  in  Hungary  ;  in  Norway,  near  Kongsberg  ;  in  the  Altai ; 
in  the  Urals  at  the  Blagodat  mine ;  in  Cornwall ;  in  Bolivia ;  Peru  ;  Chili ;  Mexico,  etc. 
Occurs  in  Nevada,  at  the  Comstock  lode,  and  elsewhere. 

OLDIIAMTTE  from  the  Busti  meteorite  is  essentially  CaS. 

NAUMANNITE. — A  silver  selenide,  containing  also  some  lead.  Color  iron-black.  From 
the  Harz. 

EUCAIRITE. — A  silver-copper  selenide,  (Cu,  Ag)2Se.  Color  silver- white  to  gray.  Sweden ; 
Chili. 

CROOKESITE. 

Massive,  compact ;  no  trace  of  crystallization. 

H.— 2-5-3.     G.=6-90.     Lustre  metallic.     Color  lead-gray.     Brittle. 

Comp.— (Cu.2,Tl,Ag)  Se= Selenium  33 '28,  copper  45-76.  thallium  17-25,  silver  3'71»100. 

Pyr.,  etc. — B.B.  fuses  very  easily  to  a  greenish-black  shining  enamel,  coloring  the  flame 
strongly  green.  Insoluble  in  hydrochloric  acid  ;  completely  soluble  in  nitric  acid. 

Obs — From  the  mine  of  Skrikerum  in  Norway.  Formerly  regarded  as  selenide  of  copper 
or  berzelianite. 

GALENITE.    Galena.     Bleiglanz,  Germ. 

Isometric  ;  habit  cubic  (see  f.  38,  39,  etc.,  p.  15).  Cleavage,  cubic,  per- 
fect;  octahedral  in  traces.  Twins:  twinning-plane,  the  octahedral  plane, 
f .  425  (f .  263,  p.  88) ;  the  same  kind  of  composition  repeated,  f .  426,  and 


214:  DESCRIPTIVE   MINERALOGY. 

flattened  parallel  to  1.     Also  reticulated,  tabular  ;  coarse  or  fine  granular  ; 
sometimes  impalpable  ;  occasionally  fibrous. 


434 


H.=2-5-2-75.  G. =7-25-7-7.  Lustre  metallic.  Color  and  streak  pure 
lead-gray.  Surface  of  crystals  occasionally  tarnished.  Fracture  flat  sub- 
chonclioidal,  or  even.  Frangible. 

'  CD 

Comp.,  Var — PbS= Sulphur  13 '4,  lead  86-6=100.  Contains  silver,  and  occasionally  selen- 
ium, zinc,  cadmium,  antimony,  copper,  as  sulphides  ;  besides,  also,  sometimes  native  silver 
and  gold  ;  all  galenite  is  more  or  less  argentiferous,  and  no  external  characters  serve  to  dis- 
tinguish the  relative  amount  of  silver  present. 

Fyr. — In  the  open  tube  gives  sulphurous  fumes.  B.B.  on  charcoal  fuses,  emits  sulphurous 
fumes,  coats  the  coal  yellow,  and  yields  a  globule  of  metallic  lead.  Soluble  in  nitric  acid. 

Diff. — Distinguished  in  all  but  the  finely  granular  varieties  by  its  perfect  cubic  cleavage. 

Obs. — Occurs  in  beds  and  veins,  both  in  crystalline  and  uncrystalline  rocks.  It  is  often 
associated  with  pyrite,  marcasite,  blende,  chalcopyrite,  arsenopyrite,  etc.,  in  a  gaugue  of 
quartz,  calcite,  barite,  or  fluorite,  etc.  ;  also  with  cerussite,  anglesite,  and  other  salts  of  lead, 
which  are  frequent  results  of  its  alteration.  It  is  also  common  with  gold,  and  in  veins  of 
silver  ores.  Some  prominent  localities  are : — Freiberg  in  Saxony,  the  Harz,  Przibram  and 
Joachimsthal,  Styria  ;  and  also  Bleiberg,  and  the  neighboring  localities  of  Carinthia,  Sala  in 
Sweden,  Leadhills  and  the  killas  of  Cornwall,  in  veins ;  Derbyshire,  Cumberland,  and  the 
northern  districts  of  England  ;  in  Nertschinsk,  East  Siberia;  in  Algeria;  near  Cape  of  Good 
Hope  ;  in  Australia ;  Chili ;  Bolivia,  etc. 

Extensive  deposits  of  this  ore  in  the  United  States  exist  in  Missouri,  Illinois,  Iowa,  and 
Wisconsin.  Other  important  localities  are : — in  New  York,  Rossie,  St.  Lawrence  Co.  ; 
Wurtzboro,  Sullivan  Co. ;  at  Ancram,  Columbia  Co.  ;  in  Ulster  Co.  In  Maine,  at  Lubec.  In 
New  Hampshire,  at  Eaton  and  other  places.  In  Vermont,  at  Thetford.  In  Connecticut,  at 
Middletown.  In  'Massachusetts,  at  Newburyport,  at  Southampton,  etc.  In  Pennsylvania,  at 
Phenixville  and  elsewhere.  In  Virginia,  at  Austin's  mines  in  Wythe  Co.,  Walton's  gold  mine 
in  Louisa  Co.,  etc.  In  Tennessee,  at  Brown's  Creek,  and  at  Haysboro,  near  Nashville.  In 
Michigan,  in  the  region  of  Chocolate  river,  and  Lake  Superior  copper  districts,  on  the 
N.  shore  of  L.  Superior,  in  Neebing  on  Thunder  Bay,  and  around  Black  Bay.  In  Cali- 
fornia, at  many  of  the  gold  mines.  In  Nevada,  abundant  on  Walker's  river,  and  at  Steam- 
boat Springs,  Galena  district.  In  Arizona,  in  the  Castle  Dome,  Eureka,  and  other  districts. 
In  Colorado,  at  Pike's  Peak,  etc. 

CLAUSTHALITE.    Selenblei,  Germ. 

Isometric.  Occurs  commonly  in  fine  granular  masses  ;  some  specimens 
foliated.  Cleavage  cubic. 

H.= 2*5-3.  G.— 7:6-8*8.  Lustre  metallic.  Color  lead-gray,  somewhat 
bluish-.  Streak  darker.  Opaque.  Fracture  granular  and  shining. 

Comp.,  Var. — PbSe= Selenium  27 '6,  lead  72'4=100.  Besides  the  pure  selenide  of  lead, 
there  are  others,  often  arranged  as  distinct  species,  which  contain  cobalt,  copper,  or  mercury, 
in  place  of  part  of  the  lead,  and  sometimes  a  little  silver  or  iron. 


215 

Pyr. — Decrepitates  in  the  closed  tube.  In  the  open  tube  gives  selenous  fumes  and  a  red 
sublimate.  B.  B.  on  charcoal  a  strong  selenous  odor  ;  partially  fuses.  Coats  the  coal  hear 
the  assay  at  first  gray,  with  a  -reddish  border  (selenium),  and  later  yellow  (lead  oxide) ;  when 
pure  entirely  volatile  ;  with  soda  gives  a  globule  of  metallic  lead. 

Obs. — Much  resembles  a  granular  galenite;  but  the  faint  tinge  of  blue  and  the  B.B. 
selenium  fumes  serve  to  distinguish  it. 

Found  at  Clausthal,  Tilkerode,  Zorge,  Lehrbach,  etc. ,  in  the  Harz  ;  at*  Remsberg  in  Sax- 
ony ;  at  the  Rio  Tinto  mines,  Spain  ;  Cacheuta  mine,  Mendoza,  S.  A. 

ZOKGITE  and  LEHRBACHITE  occur  with  clausthalite  in  the  Harz.  Zorgite  is  a  lead-copper 
selenide.  Lehrbachite  is  a  lead-mercury  selenide. 

BEHZELIANITE.— Cu2Se= Selenium  38 '4,  copper  61 '6=100.  Color  silver -white.  From 
Sweden,  also  the  Harz. 

ALT  AIT  E.— Composition  PbTe= Tellurium  38 '3,  lead  61  "17.  Isometric.  Color  tin- white. 
From  Savodinski  in  the  Altai  ;  Stanislaus  mine,  Cal. ;  Red  Cloud  mine,  Colorado ;  Province 
of  Coquimbo,  Chili. 

TIEMANNITE  (Selenquecksilber,  Oerm.}.—K  mercury  selenide,  probably  HgSe.  Massive. 
Found  in  the  Harz  ;  also  California. 


BORNITE.    Erubescite.     Purple  Copper  Ore.     Buntkupfererz,  Germ. 

Isometric.  Cleavage  :  octahedral  in  traces.  Massive,  structure  granular 
or  compact. 

H.=3.  G.=4-4-5-5.  Lustre  metallic.  Color  between  copper-red  and 
pinchbeck-brown;  speedily  tarnishes.  Streak  pale  gray ish-b Jack,  slightly 
shining.  Fracture  small  conchoidal,  uneven.  Brittle. 

C5  f 

Comp.— For  crystallized  varieties  FeCu3S3,  or  sulphur  28 '06,  iron  16'36,  copper  55 '58=100. 
Other  varieties  are  :  Fe.2Cu3S4,  FeCu5S3,  and  so  on.  The  ratio  of  R  (Cu  or  Fe)  to  S  has  the 
values  5  :  4,  4  :  3,  3  :  2,  1  :  3  (Rammelsberg).  Analysis,  Collier,  from  Bristol,  Ct.  Sulphur 
25'83,  copper  6179,  iron  11'77,  silver  tr.  =99-39  (R  :  S=3  :  2). 

Pyr.,  etc. — In  the  closed  tube  gives  a  faint  sublimate  of  sulphur.  In  the  open  tube  yields 
sulphurous  oxide,  but  gives  no  sublimate.  B.B.  on  charcoal  fuses  in  R. F.  to  a  brittle  mag- 
netic globule.  The  roasted  mineral  gives  with  the  fluxes  the  reactions  of  iron  and  copper, 
and  with  soda  a  metallic  globule.  Soluble  in  nitric  acid  with  separation  of  sulphur. 

Diff. — Distinguished  by  its  copper-red  color  on  the  fresh  fracture. 

Obs. — Found  in  the  mines  of  Cornwall ;  at  Ross  Island  in  Killarney,  Ireland  ;  at  Mount 
Catini,  Tuscany  ;  in  the  Mansfeld  district.  Germany ;  and  in  Norway.  Siberia,  Silesia,  and 
Hungary.  It  is  the  principal  copper  ore  at  some  Chilian  mines ;  also  common  in  Peru,  Boli- 
via, and  Mexico.  At  Bristol,  Conn.,  it  has  been  found  abundantly  in  good  crystals.  Found 
massive  at  Mahoopeny,  Penn. ,  and  in  other  parts  of  the  same  State  ;  also  at  Chesterfield, 
Mass.  ;  also  in  New  Jersey.  A  common  ore  in  Canada,  at  the  Acton  and  other  mines. 

ALABANDITE  (Manganglanz,  Germ.). — MnS  =  Sulphur  36'7,  manganese  63.3  =  100.  Isomet- 
ric. Cleavage  cubic.  Color  black.  Streak  green.  From  Transylvania,  etc. 

GRUNAUITE. — A  sulphide  containing  nickel,  bismuth,  iron,  cobalt,  copper.  From 
Griinau. 


(5)    Blende  Group.     Isometric  ;  tetrahedral. 

SPHALERITE  or  ZINC  BLENDE.     Black-Jack,  Engl  Miners. 

Isometric:  tetrahedral.  Cleavage:  dodecahedral,  highly  perfect.  Twins: 
twiuning-plane  1,  as  in  f.  429.  Also  botryoidal,  and  other  imitative  shapes ; 
sometimes  fibrous  and  radiated  ;  also  massive,  compact. 

H. =3-5-4:.  G.— 3*9-4-2.  4-063,  white,  New  Jersey.  Lustre  resinous 
to  adamanite.  Color  brown,  yellow,  black,  red,  green  ;  white  or  yellow 


216 


DESCRIPTIVE   MINERALOGY. 


when   pure.      Streak   white — reddish-brown.      Transparent — translucent. 
Fracture  conchoidal.     Brittle. 


428 


429 


Comp.,  Var — ZnS-=  Sulphur  33,  zinc  67=100.  But  often  having  part  of  the  zinc  replaced 
by  iron,  and  sometimes  by  cadmium ;  also  containing  in  minute  quantities,  thallium,  indium, 
and  gallium.  Var.  1.  Ordinary.  Containing  little  or  no  iron  ;  colors  white  to  yellowish- 
brown,  sometimes  black ;  G.  =3  9-4'l.  2.  Ferriferous;  Marmatite.  Containing  10  p.  c.  or 
more  of  iron;  dark-brown  to  black  ;  G.=3*9-4'2.  The  proportion  of  iron  sulphide  to  zinc 
sulphide  varies  from  1  :  5  to  1  :  2.  3.  Gadmiferous  ;  Przibramite.  The  amount  of  cadmium 
present  in  any  blende  thus  far  analyzed  is  less  than  5  per  cent.  Each  of  the  above  varieties 
may  occur  (a)  in  crystals ;  (b)  firm,  fibrous,  or  columnar,  at  times  radiated  or  plumose  ;  (6) 
cleavable,  massive,  or  foliated  ;  (d)  granular,  or  compact  massive. 

Pyr.,  etc. — In  the  open  tube  sulphurous  fumes,  and  generally  changes  color.  B.B.  on 
charcoal,  in  R.  F. ,  some  varieties  give  at  first  a  reddish-brown  coating  of  cadmium  oxide,  and 
later  a  coating  of  zinc  oxide,  which  is  yellow  while  hot  and  white  after  cooling.  With  cobalt 
solution  the  zinc  coating  gives  a  green  color  when  heated  in  O.  F.  Most  varieties,  after 
roasting,  give  with  borax  a  reaction  for  iron.  With  soda  on  charcoal  in  R.F.  a  strong  green 
zinc  flame.  Difficultly  fusible. 

Dissolves  in  hydrochloric  acid,  during  which  sulphuretted  hydrogen  is  disengaged.  Some 
specimens  phosphoresce  when  struck  with  a  steel  or  by  friction. 

Diff. — Generally  to  be  distinguished  by  its  perfect  cleavage,  giving  angles  of  60°  and  120° ; 
by  its  resinous  lustre,  and  also  by  its  infusibility. 

Obs. — Occurs  in  both  crystalline  and  sedimentary  rocks,  and  is  usually  associated  with 
galenite  ;  also  with  barite,  chalcopyrite,  fluorite,  siderite,  and  frequently  in  silver  mines. 

Derbyshire,  Cumberland,  and  Cornwall,  afford  different  varieties ;  also  Transylvania;  Hun- 
gary ;  the  Harz;  Sahla  in  Sweden;  Ratieborzitz  in  Bohemia;  many  Saxon  localities. 
Splendid  crystals  in  dolomite  are  found  in  the  Binnenthal. 

Abounds  with  the  lead  ore  of  Missouri,  Wisconsin,  Iowa,  and  Illinois.  In  _ZV.  York,  Sulli- 
van Co.,  near  Wurtzboro' ;  in  St.  Lawrence  Co.,  at  Cooper's  falls,  at  Mineral  Point;  at  the 
Ancram  lead  mine  in  Columbia  Co.  ;  in  limestone  at  Lockport  and  other  places.  In  Mass., 
at  Sterling  ;  at  the  Southampton  lead  mines  ;  at  Hatfield.  In  N.  Hamp.,  at  the  Eaton  lead 
mine  ;  at  Warren,  a  large  vein  of  black  blende.  In  Maine,  at  the  Lubec  lead  mines,  etc. 
In  Conn.,  at  Roxbury,  and  at  Lane's  mine,  Monroe.  In  JW.  Jersey,  a  white  variety  at  Frank- 
lin. In  Penn.,  at  the  Wheatley  and  Perkiomen  lead  mines  ;  near  Friedensville,  Lehigh  Co. 
In.  Virginia,  at  Austin's  lead  mines,  Wythe  Co.  In  Michigan,  at  Prince  vein,  Lake  Superior. 
In  Illinois,  near  Rosiclare  ;  near  Galena,  in  stalactites,  covered  with  pyrite,  and  galenite. 
In  Wisconsin,  at  Mineral  Point.  In  Tennessee,  at  Haysboro',  near  Nashville. 

Named  blende  because,  while  often  resembling  galena,  it  yielded  no  lead,  the  word  in  Ger- 
man meaning  blind  or  deceiving.  Sphalerite  is  from  <r<j>a\fp6s,  treacherous. 


(c)  Chalcocite  Group.     Orthorhombic. 
HESSITB.     Tellursilber,  Germ. 

Orthorhombic,  and  resembling  chalcocite.     Cleavage  indistinct, 
fii ve  ;  compact  or  fine  grained  ;  rarely  coarse-granular. 


Mas- 


SULPHIDES,  TELLURIDES,  SELENIDES,  ETC. 


217 


H.=:2-3-5.  G.=8-3-8-6.  Lustre  metallic.  Color  between  lead-gray 
and  steel-gray.  Sectile.  Fracture  even. 

Comp. — Ag2Te= Tellurium  37 '2,  silver  62 '8=100.  Silver  sometimes  replaced  in  part  by 
gold. 

Pyr. — In  the  open  tube  a  faint  white  sublimate  of  tellurous  oxide,  which  B.B.  fuses  to 
colorless  globules.  On  charcoal  fuses  to  a  black  globule  ;  this  treated  in  R.F.  presents  on 
cooling  white  dendritic  points  of  silver  on  its  surface  ;  with  soda  gives  a  gl  >bule  of  silver. 

Obs. — Occurs  in  the  Altai,  in  Siberia,  in  a  talcose  rock  ;  at  Nagyag  in  Transylvania,  and  at 
Retzbanya  in  Hungary ;  Stanislaus  mine,  Calaveras  Co. ,  Cal. ;  Red  Cloud  mine,  Colorado ; 
Province  of  Coquirabo,  Chili. 

PETZITE. — Differs  from  hessite  in  that  gold  replaces  much  of  the  silver.  H.  ^2 '5.  G.= 
8  "72-8 '83,  Petz  ;  9-9 '4,  Kiistel.  Color  between  steel-gray  and  .iron-black,  sometimes  with 
pavonine  tarnish.  Streak  iron -black.  Brittle.  Analysis  by  G-enth,  from  G-oiden  Rule  mine, 
tellurium  32  "68,  silver  41 '86,  gold  25 '60= 100 14.  Occurs  at  the  localities  stated  above,  with 
other  ores  of  tellurium. 

TAPALPITB  (Tellurwismuthsilber). — Composition  (Ramm.),  Ag2Bi2Te2S(Ag2S-|-2BiTe). 
Granular.  Color  gray.  Sierra  de  Tapalpa,  Mexico. 

ACANTHITE. 

Orthorhombic.  7  A  1  =  110°  54-' ;  0  A  14  —  124°  42',  Dauber ;  c  :  I  :  d 
=  1-4442  :  1-4523  :  1.  O  A  1-2  =  135°  10' ;  O  A  1  =  119°  42'.  Twins  : 
parallel  to  14.  Crystals  usually  slender-pointed  prisms.  Cleavage  indis- 
tinct. 

H.=2-5  or  under.  G.= 7*16-7-33.  Lustre  metallic.  Color  iron-black 
or  like  argentite.  Fracture  uneven,  giving  a  shining  surface.  Sectile. 

Comp. — Ag2S,  or  like  argentite.     Sulphur  12 "9,  silver  87 '1=100. 

Pyr. — Same  as  for  argentite,  p.  213. 

Obs. —  Found  at  Joachimsthal ;  also  near  Freiberg  in  Saxony. 


CHALCOCITE.     Chalcosine.     Vitreous  Copper.     Copper  Glance.     Kupferglanz,  Germ* 

Orthorhombic.  /A  7=  119°  35',  0  A  14  =  120°  57';  c  :  l>  :  a  =  1-6676  : 
1-7176  :  1 ;  O  A 1  =  117°  24' ;  O  A  l-i  =  135°  52'.  Cleavage  :  7,  indistinct. 
Twins  :  t winning-plane,  7,  producing  hexagonal,  or  stellate  forms  (left  half 

430  431  432  433 


Bristol,  Ct.  Bristol,  Ct.  Bristol,  Ct. 

of  f.  432)  ;  also  f-£,  a  cruciform  twin  (f.  432),  crossing  at  angles  of  111° 
f.  433,  a  cruciform  twin,  having   O  and  7  of  one  crystal  parallel 


and  69C 

respectively  to  i4  and   O  of  the  other. 

or  compact  and  impalpable. 


Also  massive,  structure  granular, 


218  DESCBIPTTVE   MINERALOGY. 

H.  — 2-5-3.  G.=5-5-5-8.  Lustre  metallic.  Color  and  streak  blackish 
lead-gray  ;  often  tarnished  blue  or  green  ;  streak  sometimes  shining.  Frac- 
ture conchoidal. 

Comp. — Cu2S  =  Sulphur  20'2,  copper  79 -8 =100. 

Pyr,,  etc. — Yie'ds  nothing  volatile  in  the  closed  tube.  In  the  open  tube  gives  off  sulphur- 
ous fumes.  B.B.  on  charcoal  melts  to  a  globule,  which  boils  with  spirting;  with  soda  is 
reduced  to  metallic  copper.  Soluble  in  nitric  acid. 

Obs. — Cornwall  affords  splendid  crystals.  The  compact  and  massive  varieties  occur  in 
Siberia,  Hesse,  Saxony,  the  Bannat,  etc.  ;  Mt.  Catini  mines  in  Tuscany ;  Mexico,  Peru, 
Bolivia,  Chili. 

In  the  United  States,  it  has  been  found  at  Bristol,  Conn. ,  in  large  and  brilliant  crystals. 
In  Virginia,  in  the  United  States  copper  mine  district,  Orange  Co.  Between  Newmarket  and 
Taneytown,  Maryland.  In  Arizona,  near  La  Paz  ;  in  N.  W.  Sonora.  In  Nevada,  in  Washoe, 
Humboldt.  Churchill,  and  Nye  Cos. 

HARRISITE  of  Shepard,  from  Canton  mine,  Georgia,  is  chalcocite  with  the  cleavage  of 
galenite  (pseudomorphous,  Genth). 

STROMEYERITE,     Silberkupferglanz,  Germ. 

Orthorhombic :  isomorphous  with  chalcocite.  /A/=119°  35'.  Also 
massive,  compact. 

H.= 2-5-3.  G.= 6-2-6-3.  Lustre  metallic.  Color  dark  steel-gray. 
Streak  shining.  Fracture  subconchoidal. 

Comp, — AgCuS=Ag2S  +  Cu2S=Sulphur  15'7,  silver  53-1,  copper  31'2— 100. 

Pyr.,  etc. — Fuses,  but  gives  no  sublimate  in  the  closed  tube.  In  the  open  tube  sulphurous 
fumes.  B.B.  on  charcoal  in  O.F.  fuses  to  a  semi-malleable  globule,  which,  treated  with  the 
fluxes,  reacts  strongly  for  copper,  and  cupelled  with  lead  gives  a  silver  globule.  Soluble  in 
nitric  acid. 

Obs. — Found  at  Schlangenberg,  in  Siberia  ;  at  Rudelstadt,  Silesia  ;  also  in  Chili ;  at  Com- 
bavalla  in  Peru  ;  at  Heintzelman  mine  in  Arizona. 

STERNBERGITE.  — An  iron-silver  sulphide,  AgFe^S2.  Johanngeorgenstadt  and  JoachimsthaL 


.  (d)  Pyrrhotite  Group.     Hexagonal. 
CINNABAR.    Zinnober,  Germ. 

Khombohedral.  R  A  R  =  92°  36',  II A  O  =  127°  6' ;  c  =  1-1448.  Ac- 
cording to  DesCloizeaux,  tetartohedral,  like  quartz. 
434  Also  granular,  massive ;  sometimes  forming  super- 

ficial coatings. 

Cleavage :  /,  very  perfect.  Twins :  twinning- 
plane  O. 

H=2-2-5.  G=:8-998,  a  cleavable  variety  from 
Neumarktel.  Lustre  adamantine,  inclining  to  metal- 
lic when  dark-colored,  and  to  dull  in  friable 
varieties.  Color  cochineal-red,  often  inclining  to 
brownish-red  and  lead-gray.  Streak  scarlet,  sub- 
transparent,  opaque.  Fracture  subconchoidal,  un- 
even. Sectile.  Polarization  circular. 

Comp.— HgS  (or  Hg3S3)rrSulphur  13'8,  mercury  86 '2=100.  Sometimes  impure  from  clay, 
iron  sesquioxide,  bitumen. 


SULPHIDES,    TELLUKIDES,    SELENIDES,    ETC.  219 

Pyr. — In  the  closed  tube  a  black  sublimate.  Carefully  heated  in  the  open  tube  gives  aul- 
phurous  fumes  and  metallic  mercury,  condensing  in  minute  globules  on  the  cold  walls  of  the 
tube.  B.B.  on  charcoal  wholly  volatile  if  pure. 

Obs. — Cinnabar  occurs  in  beds  in  slate  rocks  and  shales,  and  rarely  in  granite  or  porphyry. 
It  has  been  observed  in  veins,  with  ores  of  iron.  The  most  important  European  beds  of  this 
ore  are  at  Almaden  in  Spain,  and  at  Idria  in  Carniola.  It  occurs  at  Reichenau  and  Windisch 
Kappel  iij  Caririthia ;  in  Transylvania ;  at  Ripa  in  Tuscany ;  at  Schemnitz  in  Hungary ;  in 
the  Urals  and  Altai ;  in  China  abundantly,  and  in  Japan  ;  San  Onofre  and  elsewhere  in  Mexico ; 
in  Southern  Peru ;  forming  extensive  mines  in  California,  in  the  coast  ranges  the  principal 
mines  are  at  New  Almaden  and  the  vicinity,  in  Santa  Clara  Co.  Also  in  Idaho,  in  limestone, 
abundant. 

This  ore  is  the  source  of  the  mercury  of  commerce,  from  which  it  is  obtained  by  sublima- 
tion. When  pure  it  is  identical  with  the  manufactured  vermilion  of  commerce. 

METACINNABARITE  (Moore). — A  black  mercury  sulphide  (HgS).  Barely  crystallized. 
H.  —  3.  Gr.  =7'75.  Lustre  metallic.  Redington  mine,  Lake  Co.,  Cal. 

(TAUDALCAZARITE. — Essentially  HgS,  with  part  (-,^)  of  the  sulphur  replaced  by  selenium, 
and  part  of  the  mercury  replaced  by  zinc  (Hg  :  Zn=6  : 1,  Petersen  ;  —13  : 1,  Ramm.).  Massive. 
Color  deep  black.  Guadalcazar,  Mexico.  LEVIGLIANITE  is  a  ferruginous  variety  from 
Levigliani,  Italy. 


MILLERITE.     Capillary  Pyrites.     Haarkies  ;  Nickelkies,  Germ. 

Ehombohedral.  R/\R  =  144°  8',  Miller,  c  =  0-32955.   O  A  R  =  159°  10'. 

Cleavage :  rhombohedral,  perfect.  Usual  in  capillary  crystals.  Also  in 
columnar  tufted  coatings,  partly  serai-globular  and  radiated. 

H.  — 3-3-5.  G.  =  4-6-5-65.  Lustre  metallic.  Color  brass-bellow,  inclin- 
ing to  bronze-yellow,  with  often  a  gray  iridescent  tarnish.  Streak  bright. 
Brittle. 

Comp.— MS = Sulphur  35  6,  nickel  64  A— 100. 

Pyr.,  etc. — In  the  open  tube  sulphurous  fumes.  B.  B.  on  charcoal  fuses  to  a  globule.  When 
roasted,  gives  with  borax  and  salt  of  phosphorus  a  violet  bead  in  O.F. ,  becoming  gray  in  R.F. 
from  reduced  metallic  nickel.  On  charcoal  in  R.F.  the  roasted  mineral  gives  a  coherent 
metallic  mass,  attractable  by  the  magnet.  Soluble  in  nitric  acid. 

Obs.— Found  at  Joachimst-hal ;  Przibram  ;  Riechelsdorf  ;  Andreasberg  ;  several  localities 
in  Saxony  ;  Cornwall. 

Occurs  at  the  Sterling  mine,  Antwerp,  'JM".  Y.  ;  in  Lancaster  Co.,  Pa.,  at  the  Gap  mine ; 
with  dolomite,  and  penetrating  calcite  crystals,  in  cavities  in  limestone,  at  St.  Louis,  Mo. 

BEYRICHITE  (Hebe).— Formula  Ni5S7  =  Sulphur  43-6,  nickel  56-4—100.  Color  lead-gray. 
Occurs  in  radiated  groups  with  millerite  in  the  Westerwald. 


PYRRHOTITE.     Magnetic  Pyrites.     Magnetkies,   Germ. 

Hexagonal.     O  A  1  —  135°    8' ;    c  —  0-862.      Twins :   twinning-plane    1 
(f.  435).  Cleavage :  O,  perfect ;  I,  less  so.  Commonly 
massive  and  amorphous;  structure  granular. 

H.= 3-5-4-5.  G.= 4-4-4-68.  Lustre  metallic. 
Color  between  bronze-yellow  and  copper-red,  and 
subject  to  speedy  tarnish.  Streak  dark  grayish- 
black.  Brittle.  Magnetic,  being  attractable  in 
fine  powder  by  a  magnet,  even  when  not  affecting 
an  ordinary  needle. 

Comp.— (1)  Mostly  Fe7S8:=  Sulphur  39-5,  iron  60'5=100  ;  but  varying  to  Fe8S9,Fe9S10  and 
Fe ,  0S , ! .     Some  varieties  contain  3-6  p.  c.  nickel.     Horbachite  contains  (Wagner)  1 2  p.  c.  Ni. 
Pyr.,  etc. — Unchanged  in  the  closed  tube.     In  the  open  tube  gives  sulphurous  oxide.     On 


220  DESCRIPTIVE   MINERALOGY. 

charcoal  in  R.  F.  fuses  to  a  black  magnetic  mass ;  in  O.  F.  is  converted  into  iron  sesquioxide, 
which  with  fluxes  gives  only  an  iron  reaction  when  pure,  but  many  varieties  yield  small 
amounts  of  nickel  and  cobalt.  Decomposed  by  muriatic  acid,  with  evolution  of  sulphuretted 
hydrogen. 

Diff. — Distinguished  by  its  magnetic  character,  and  by  its  bronze  color  on  the  fresh  fracture. 

Obs. — Occurs  in  Norway  ;  in  Sweden ;  at  Andreasberg;  Bodenmaisin  Bavaria  ;  N.  Tagilsk  ; 
in  Spain  ;  the  lavas  of  Vesuvius  ;  Cornwall. 

In  N.  America,  in  Vermont,  at  Stafford,  Corinth,  and  Shrewsbury  ;  in  many  parts  of 
Massachusetts ;  in  Connecticut,  in  Trumbull,  in  Monroe  ;  in  1ST.  York,  near  Natural  Bridge 
in  Diana,  Lewis  Co.  ;  at  O'Neil  mine  and  elsewhere  in  Orange  Co.  In  N.  Jersey,  Morris  Co., 
at  Hurdstown.  In  Pennsylvania,  at  the  Gap  mine,  Lancaster  Co. ,  niccoliferous.  In  Tennes- 
see, at  Ducktown  mines.  In  Canada,  at  St.  Jerome;  Elizabethtown,  Ontario  (f.  435),  etc. 

The  niccoliferous  pyrrhotite  is  the  ore  that  affords  the  most  of  the  nickel  of  commerce. 

TROILITE. — According  to  the  latest  investigations  of  J.  Lawrence  Smith,  composition 
FeS,  iron  proto-sulphide  ;  that  is,  iron  63 '6,  sulphur  36*4=100.  Occurs  only  in  iron  meteor- 
ites. DAUBRKELITB  (Smith). — Composition  CrS.  Observed  in  the  meteoric  iron  of  Northern 
Mexico  ;  occurring  on  the  borders  of  troilite  nodules.  Similar  to  shepardite,  Haidinger 
(=sckreibersite,  Shepard),  described  by  Shepard  (1846)  as  occurring  in  the  Bishopville,  S.  C., 
meteoric  iron. 

SCHREIBBRSITE  also  solely  a  meteoric  mineral.     Contains  iron,  nickel,  and  phosphorus. 

WURTZITE  (Spiauterite). — ZnS,  like  sphalerite,  but  hexagonal  in  crystallization.     Bolivia. 


GREENOCKITE. 


Hexagonal  ;  hemimorphic.  OM  =  136°  24'  ;  c  =  0-824:7.  Cleavage: 
J,  distinct  ;  (9,  imperfect. 

H.:=3-3-5.  G.  =  4-8-4-999.  Lustre  adamantine.  Color  honey-yellow; 
citron-yellow  ;  orange-yellow  —  veined  parallel  'with  the  axis  ;  bronze- 
yellow.  Streak-powder  between  orange-yellow  and  brick  red.  Nearly 
transparent.  Strong  double  refraction.  Not  thermoelectric,  Breithaupt. 

Comp.  —  CdS  (or  Cd3Ss)  =  Sulphur  22-2,  cadium  77  '8. 

Pyr.,  etc.—  In  the  closed  tube  assumes  a  carmine-red  color  while  hot,  fading  to  the  original 
yellow  on  cooling.  In  the  open  tube  gives  sulphurous  oxide.  B.B.  on  charcoal,  either  alone 
or  with  soda,  gives  in  R.F.  a  reddish-brown  coating.  Soluble  in  hydrochloric  acid,  evolving 
sulphuretted  hydrogen. 

Obs.  —  Occurs  at  Bishoptown,  in  Renfrewshire,  Scotland  ;  also  at  Przibram  in  Bohemia  ; 
on  sphalerite  at  the  Ueberoth  zinc  mine,  near  Friedensville.  Lehigb  Co.,  Pa.,  and  at  Granby, 
Mo. 


NICOOLITE.     Copper  Nickel.     Kupfernickel,  Rothnickelkies,  Germ. 

Hexagonal.  O  A  1  =  13°6  35' ;  c:  0-81944.  Usually  massive,  structure 
nearly  impalpable  ;  also  reniform  with  a  columnar  structure ;  also  reticu- 
lated and  arborescent. 

PL =5-5-5.  G.= 7-33-7-671.  Lustre  metallic.  Color  pale  copper-red, 
with  a  gray  to  blackish  tarnish:  Streak  pale  brownish-black.  Opaque, 
Fracture  uneven.  Brittle. 

Oomp — NiAs  (or  Ni8As8)= Arsenic  56  -4,  nickel  43-6=100;  sometimes  part  of  the  arsenic 
replaced  by  antimony. 

Pyr.,  etc.— In  the  closed  tube  a  faint  white  crystalline  sublimate  of  arsenous  oxide.  In  the 
open  tube  arsenous  oxide,  with  a  trace  of  sulphurous  oxide,  the  assay  becoming  yellowish- 
green.  On  charcoal  gives  arsenical  fumes  and  fuses  to  a  globule,  which,  treated  with  borax 
glass,  affords,  by  successive  oxidation,  reactions  for  iron,  cobalt,  and  nickel.  Soluble  in 
mtro-hydrochloric  acid. 

Diff. — Distinguished  by  its  color  from  other  similar  sulphides,  as  also  by  its  pyrognostics. 


221 

Obs. — Occurs  at  several  Saxon  mines,  also  in  Thuringia,  Hesse,  and  Styria,  and  at  Alle- 
mont  in  Dauphiny ;  occasionally  in  Cornwall ;  Chili ;  abundant  at  Mina  de  la  Rioja,  in  the 
Argentine  Provinces.  Found  at  Chatham,  Conn.,  in  gneiss,  associated  with  smaltite. 

BKEITHAUPTITE. — Composition  NiSb= Antimony  07 '8,  nickel  32  "2=100.  Color  light 
copper-red.  Andreasberg. 

AIUTE.— An  antimoniferous  niccolite,  containing  28  p.  c.  Sb.  Basses-Pyrenees  ;  Wolfach, 
Baden. 


C.    DEUTO    OR    PYBITE    DIVISION.4 

(a)  Pyrite  Group. 

PYRITB.    Iron  Pyrites.     Schwefelkies,  Eisenkies,  Germ. 

Isometric  ;  pyritohedral.  The  cube  the  most  common  form ;  the  pyrito- 
hedron,  f.  92,  p.  23.  and  related  forms,  f.  94,  95,  96,  also  very  common. 
See  also  f.  103,  104,  105,  p.  24.  Cubic  faces  often  striated,  with  striations 
of  adjoining  faces  at  right  angles,  and  due  to  oscillatory  combination  of  the 
cube  and  pyritohedron,  the  stride  having  the  direction  of  the  edges  between 
O  and  i-%.  Crystals  sometimes  acicular  through  elongation  of  cubic  and 
other  forms.  Cleavage  :  cubic  and  octahedral,  more  or  less  distinct.  Twins: 
twining-plane  /,  f.  276,  p.  93.  Also  reniform,  globular,  stalactitic,  with  a 
crystalline  surface;  sometimes  radiated  subfibrous.  Massive. 


436  437  438 


Rossie. 


IT.  =6-6-5.  G.  =4-83-5-2.  Lustre  metallic,  splendent  to  glistening. 
Color  a  pale  brass-yellow,  nearly  uniform.  Streak  greenish  or  brownish- 
black.  Opaque.  Fracture  conchoidal,  uneven.  Brittle.  Strikes  fire  with 

steel. 


ar.  —  FeS2  —  Sulphur  53'3,  iron  46-7=100.  Nickel,  cobalt,  and  thallium,  and  also 
copper,  sometimes  replace  a  little  of  the  iron,  or  else  occur  as  mixtures  ;  and  gold  is  some- 
times present,  distributed  invisibly  through  it. 

Pyr.,  etc.  —  In  the  closed  tube  a  sublimate  of  sulphur  and  a  magnetic  residue.  B.B.  on 
charcoal  gives  off  sulphur,  burning  with  a  blue  flame,  leaving  a  residue  which  reacts  like 
pyrrhotite.  Insoluble  in  hydrochloric  acid,  but  decomposed  by  nitric  acid. 

"DifiF.  —  Distinguished  from  chalcopyrite  by  its  greater  hardness,  since  it  cannot  be  cut  with 
a  knife  ;  as  also  by  its  pale  color  ;  from  marcasite  by  its  specific  gravity  and  color.  Not 
malleable  like  gold 

Obs.  —  Pyrite  occurs  abundantly  in  rocks  of  all  ages,  from  the  oldest  crystalline  rocks  to  the 


DESCRIPTIVE   MINEKALOGY. 


most  recent  alluvial  deposits.  It  usually  occurs  in  small  cubes,  also  in  irregular  spheroidal 
nodules  and  in  veins,  in  clay  slate,  argillaceous  sandstones,  the  coal  formation,  etc.  The 
Cornwall  mines,  Alston-Moor,  Derbyshire,  Fahlun  in  Sweden,  Kongsberg  in  Norway.  Elba, 
Traversella  in  Piedmont,  Peru,  are  well -known  localities. 

Occurs  in  New  England  at  many  places  :  as  the  Vernon slate  quarries  ;  Roxbury,  Conn.,  etc. 
In  JV.  York,  at  Rossie,  at  Schoharie;  in  Orange  Co.,  at  Warwick  and  Deerpark,  and  many 
other  places.  In  Pennsylvania,  at  Little  Britain,  Lancaster  Co.  ;  at  Chester,  Delaware  Co  ; 
in  Carbon,  York,  and  Chester  Cos. ;  at  'Cornwall,  Lebanon  Co.,  etc.  In  Wisconsin,  near 
Mineral  Point.  In  N.  Car.,  near  Greensboro',  G-uilford  Co.  Auriferous  pyrite  is  common  at 
the  mines  of  Colorado,  and  many  of  those  of  California,  as  well  as  in  Virginia  and  the  States 
south. 

This  species  affords  a  considerable  part  of  the  iron  sulphate  and  sulphuric  acid  of  commerce, 
and  also  much  of  the  sulphur  and  alum.  The  auriferous  variety  is  worked  for  gold  in  many 
gold  regions. 

The  namepyritt  is  derived  from  ?n>,  fire,  and  alludes  to  the  sparks  from  friction. 

HAUERITE. — Composition  MnS2  =  Sulphur  58*7,  manganese  46 '3 =100.  Isometric.  Color 
reddish-brown.  Kalinka,  Hungary. 


CHALCOPYRITE.     Copper  Pyrites.     Kupferkies,  Germ. 


Tetragonal ;  tetrabedral.  O  A  l-i  =  135°  25';  c  =  0-98556  ;  0  A  1  =  125° 
40' ;  1  A  1,  pyr.,  =  109°  53' ;  1  A  1  (f.  440)  =  71°  20'  and  70°  7'.  Cleav- 
age :  %-i  sometimes  distinct ;  O,  indistinct.  Twins  :  twinning-plane  1-i  ; 
the  plane  1  (see  p.  94).  Often  massive. 


440 


441 


H.=3'5-4r.  G.=4r'l-4*3.  Lustre  metallic.  Color  brass-yellow ;  subject 
to  tarnish,  and  often  iridescent.  Streak  greenish-black — a  little  shining. 
Opaque.  Fracture  conchoidal,  uneven. 

Comp, — CuFeS 2  =  Sulphur  34-9,  copper  34 '6,  iron  30*5=100.  Some  analyses  give  other 
proportions  ;  bub  probably  from  mixture  with  pyrite.  There  are  indefinite  mixtures  of  the 
two,  and  with  the  increase  of  the  latter  the  color  becomes  paler. 

This  species,  although  tetragonal,  is  -very  closely  isomorphous  with  pyrite,  the  variation 
from  the  cubic  form  being  slight,  the  vertical  axis  being  0*98556  instead  of  1. 

Traces  of  selenium  have  been  noticed  by  Kersten  in  an  ore  from  Reinsberg  near  Freiberg. 
Thallium  is  also  present  in  some  kinds,  and  more  frequently  in  this  ore  than  in  pyrite. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  and  gives  a  sulphur  sublimate  ;  in  the  open 
tube  sulphurous  oxide.  B.B.  on  charcoal  gives  sulphur  fumes  and  fuses  to  a  magnetic  glo 
bule.  The  .roasted  ore  reacts  for  copper  and  iron  with  the  fluxes ;  with  soda  on  charcoal 
gives  a  globule  of  metallic  iron  with  copper.  Dissolves  in  nitric  acid,  excepting  the  sulphur, 
and  forms  a  green  solution  ;  ammonia  in  excess  changes  the  green  color  to  a  deep  blue. 

Diff, — Distinguished  from  pyrite  by  its  inferior  hardness,  it  can  be  easily  scratched  with 
the  knife ;  and  by  its  deeper  color.  Not  malleable  like  gold,  from  which  it  differs  also  in 
being  decomposed  by  nitric  acid. 


SULPHIDES,    TELLURIDES,    SELENIDES,    ETC.  223 

Obs. — Chalcopyrite  is  the  principal  ore  of  copper  at  the  Cornwall  mines.  Occurs  at  Frei- 
berg- ;  in  the  Bannat ;  Hungary ;  and  Thuringia  ;  in  Scotland  ;  in  Tuscany  ;  in  South  Australia ; 
in  fine  crystals  at  Cerro  Blanco,  Chili. 

A  common  mineral  in  America,  some  localities  are  :  Stafford,  Yt.  ;  Rossie,  Ellenville,  N.  Y. ; 
Phenixville,  etc. ,  Perm.  The  mines  in  North  Carolina  and  eastern  Tennessee  afford  large 
quantities.  Occurs  in  Gal. ,  in  different  mines  along  a  belt  between  Mariposa  Co.  and  Del  Norte 
Co.,  on  west  side  of,  and  parallel  to,  the  chief  gold  belt ;  occurring  massive  in  Calaveras  Co.; 
in  Mariposa  Co.,  etc.  In  Canada,  in  Perth  and  near  Sherbrooke;  extensively  mined  at 
Bruce  mines,  on  Lake  Huron. 

Named  from  %aA./cos,  brass,  and  pyrites,  by  Henckel,  who  observes  in  his  Pyritology  (1725) 
that  chalcopyrite  is  a  good  distinctive  name  for  the  ore. 

CUBANITE  is  CuFe2S4,  or  CuFe2S3  (Scheidhauer). — Occurs  massive  at  Barracanao,  Cuba; 
Tunaberg,  Sweden. 

BAKNHARDTITE,  from  North  Carolina. — Composition  uncertain,  perhaps  Cu4Fe2S5.  It  may 
be  partly  altered  from  chalcopyrite. 

STANNITE  (Zinnkies,  Germ.}. — A  sulphide  containing  26  p.  c.  tin ;  also  copper,  iron,  and 
zinc.  Massive.  Color  steel-gray.  Chiefly  from  Cornwall,  also  Ziunwald. 


LINNJEITE.    Kobaltnickelkies,  Germ. 

Isometric.  Cleavage :  cubic,  imperfect.  Twins  :  t winning-plane  octa- 
hedral. Also  massive,  granular  to  compact. 

H.  =  5'5.  G.= 4-8-5."  Lustre  metallic.  Color  pale  steel-gray,  tarnishing 
copper-red.  Streak  blackish-gray.  Fracture  uneven  or  subconchoidal. 

Comp  —  CosS4  (or  2CoS+CoS2)= Sulphur  42*0,  cobalt  58-0=100  ;  but  having  the  cobalt 
replaced  partly  by  nickel  or  copper,  the  proportions  varying  very  much.  The  Miisen  ore 
(siegenite)  contains  30-40  p.  c.  of  nickel. 

Fyr.,  etc — The  variety  from  Miisen  gives,  in  the  closed  tube,  a  sulphur  sublimate  ;  in  the 
open  tube,  sulphurous  fumes,  with  a  faint  sublimate  of  arsenous  oxide.  B.B.  on  charcoal 
gives  arsenical  and  sulphurous  odors,  and  fuses  to  a  magnetic  globule.  The  roasted  mineral 
gives  with  the  fluxes  reactions  for  nickel,  cobalt,  and  iron.  Soluble  in  nitric  acid,  with  separa- 
tion  of  sulphur. 

Diff, — Distinguished  by  its  color,  and  isometric  crystallization. 

Obs, — In  gneiss,  at  Bastnaes,  Sweden;  at  Miisen,  near  Siegen,  in  Prussia;  at  Siegen 
(siegenite),  in  octahedrons;  at  Mine  la  Motte,  in  Missouri,  mostly  massive,  also  crystalline  • 
and  at  Mineral  Hill,  in  Maryland. 


SMALTITE.    Speiskobalt,  Germ. 

Isometric.  Cleavage  :  octahedral,  distinct ;  cubic,  in  traces.  Also  mas- 
sive and'in  reticulated  and  other  imitative  shapes. 

H.  =  5-5-6.  G.  =  6*4:to7'2.B'  Lustre  metallic.  Color  tin-white,  inclining, 
when  massive,  to  steel-gray,  sometimes  iridescent,  or  grayish  from  tarnish. 
Streak  grayish-black.  Fracture  granular  and  uneven.  Brittle. 

Comp.,  Var. — For  typical  kind  (Co,Fe,Ni)As2  =  (if  Co,  Fe,  and  Ni  be  present  in  equal 
parts)  Arsenic  72*1,  cobalt  9 '4,  nickel  9 '5,  iron  9-0=100.  It  is  probable  that  nickel  is  never 
wholly  absent,  although  not  detected  in  some  of  the  earlier  analyses  ;  and  in  some  kinds  it  is 
the  principal  metal.  The  proportions  of  cobalt,  nickel,  and  iron  vary  much. 

The  following  analyses  will  serve  as  examples  of  the  different  varieties  : 

As        Co  Ni         Fe         Cu 

1.  Schneeberg  70'37  13'95  1'79  11  "71  1*39  S  0'66,  BiO'01=99'88  Hofmann. 

2.  Allemont  (doanthite)    71 '11  1871       6-82  S  2'29=98'93  Rammelsberg. 

3.  Biechelsdorf  6042  10'80  25'87      0'80  8211  =  100. 

4.  Schneeberg  74'80      3'79  12-86      7'33  S  0-85=99-63  Karstedt 


224:  DESCRIPTIVE   MINERALOGY. 

Pyr.,  etc. — In  the  close  tube  gives  a  sublimate  of  metallic  arsenic ;  in  the  open  tube  a 
white  sublimate  of  arsenous  oxide,  and  sometimes  traces  of  sulphurous  oxide.  B.B.  on  char- 
coal gives  an  arsenical  odor,  and  fuses  to  a  globule,  which,  treated  with  successive  portions 
of  borax-glass,  affords  reactions  for  iron,  cobalt,  and  nickel. 

Obs. — Usually  occurs  in  veins,  accompanying  ores  of  cobalt  or  nickel,  and  ores  of  silver 
and.  copper  ;  also,  in  some  instances,  with  niccolite  and  arsenopyrite  ;  often  having  a  coating 
of  annabergite. 

Occurs  at  Schneeberg,  etc. ,  in  Saxony  ;  at  Joachimsthal ;  also  at  Wheal  Sparnon  hi  Corn- 
wall'; at  Riechelsdorf  in  Hesse;  at  Tunaberg  in  Sweden;  Allemont  in  Dauphine.  Also  in 
crystals  at  Mine  La  Motte,  Missouri.  At  Chatham,  Conn. ,  the  chloanthite  (chathamite)  occurs 
in  mica  slate,  associated  generally  with  arsenopyrite  and.  sometimes  with  niccolite. 

SPATHIOPYRITE  is  closely  allied  to  smaltite,  with  which  it  occurs  at  Bieber  in  Hessen. 

SKUTTEE.UDITE  (Tesseralkies,  Germ.}. — CoAs3=  Arsenic  79 '2,  cobalt  20 '8 =100.  Isometric. 
Skutterud,  Norway. 


COBALTITE.    Glance  Cobalt.     Kobaltglanz,  Germ. 

Isometric  ;  pyritohedral.  Commonly  in  pyritohedrons  (f.  92,  95,  etc., 
p.  23).  Cleavage :  cubic,  perfect.  Planes  O  striated.  Also  massive, 
granular  or  compact. 

H.  =  5'5.  G.  =  6-6'3.  Lustre  metallic.  Color  silver-white,  inclined  to 
red  ;  also  steel-gray,  with  a  violet  tinge,  or  grayish-black  when  containing 
much  iron.  Streak  grayish-black.  Fracture  uneven  and  lamellar.  Brittle. 

Comp.,  Var. — CoAsS  (or  CoSa  +  CoAs,)= Sulphur  19 '3,  arsenic  45 '2,  cobalt  35'5=100.  The 
cobalt  is  sometimes  largely  replaced  by  iron,  and  sparingly  by  copper. 

Pyr.,  etc. — Unaltered  in  the  closed  tube.  In  the  open  tube,  gives  sulphurous  fumes  and 
a  crystalline  sublimate  of  arsenous  oxide.  B.B.  on  charcoal  gives  off  sulphur  and  arsenic, 
and  fuses  to  a  magnetic  globule  ;  with  borax  a  cobalt-blue  color.  Soluble  in  warm  nitric  acid, 
separating  arsenous  oxide  and  sulphur. 

Diff.—  Distinguished  by  its  reddish-white  color ;   also  by  its  pyritohedral  form. 

Obs. — Occurs  at  Tunaberg,  Hokansbo,  in  Sweden  ;  also  at  Skutterud  in  Norway.  Other 
localities  are  at  Querbach  in  Silesia,  Siegen  in  Westphalia,  and  Botallack  mine,  in  Cornwall. 
The  most  productive  mines  are  those  of  Vena  in  Sweden. 

This  species  and  smaltite  afford  the  greater  part  of  the  smalt  of  commerce.  It  is  also 
employed  in  porcelain  painting. 


GERSDORFFITE.    Nickelarsenikkies,  Arseniknickelglanz,  Germ. 

Isometric  ;  pyritohedral.  Cleavage  :  cubic,  rather  perfect.  Also  lamel- 
lar and  granular  massive. 

H.  =  5-5.  G.  =  5-.6-6*9.  Lustre  metallic.  Color  silver- white — steel- 
gray,  often  tarnished  gray  or  grayish-black.  Streak  grayish-black.  Frac- 
ture uneven. 

Comp.,  Var.— Normal,  NiAsS  (or  NiS2+NiAs.2)~ Arsenic  45 '5,  sulphur  19'4,  nickel  35'1  = 
100.  The  composition  varies  in  atomic  proportions  rather  widely. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  and  gives  a  yellowish-brown  sublimate  of 
arsenic  sulphide.  In  the  open  tube  yields  sulphurous  fumes,  and  a  white  sublimate  of  arsen- 
ous oxide.  B.B.  on  charcoal  gives  sulphurous  and  garlic  odors  and  fuses  to  a  globule,  which, 
with  borax-glass,  gives  at  first  an  iron  reaction,  and,  by  treatment  with  fresh  portions  of  tho 
flux,  cobalt  and  nickel  are  successively  oxidized. 

Decomposed  by  nitric  acid,  forming  a  green  solution,  with  separation  of  sulphur  and  arsen- 
ous oxide. 

Obs.— Occurs  at  Loos  in  Sweden  ;  in  the  Harz  ;  at  Schladming  in  Styria  ;  Kamsdorf  iu 
Lower  Thuringia ;  Haueisen,  Voigbland  ;  near  Ems.  Also  found  as  an  incrustation  at 
Phenixville,  Pa. 


SULPHIDES,    TELLURIDES,    SELENIDES,    EtC.  225 

ULLMANNITE.— NiSbS  (NiS2+NiSb2)=  Antimony  57*2,  sulphur  15 -1,  nickel  27 '7=100. 
Generally  contains  also  some  arsenic.  Color  steel-gray.  Siegen,  Harzgerode,  etc. 

CORYNITE. — Ni(As,Sb)S,  but  the  arsenic  (38  p.  c.)  in  excess  of  the  antimony.  Olsa,  Corin- 
thia.  WOLFACHITE  (Petersen),  from  Wolfach,  Baden,  is  similar  in  composition,  but  is 
orthorhombic  in  form. 

LAURITE. — An  osmium-ruthenium  sulphide.  Analysis  (Wohler)  Sulphur  31 '79  [Osmium 
3 -03],  Ruthenium  05.18=100.  Occurs  in  minute  octahedrons  from  the  platinum- washings 
of  Borneo  ;  as  also  those  in  Oregon. 


(6)  Marcasite  Group.     Orthorhombic. 


MARCASITE.    White  Iron  Pyrites.     Strahlkies,  etc.,  Germ. 

Orthorhombic.  /A  1=  106°  5',  0  A  1-i  =  122°  26',  Miller ;  c  :  I :  &  = 
1-5737  :  1-3287  :  1.  0  A 1  =  116°  55' ;  0  A  \4 
=  130°  10'.  Cleavage:  /rather  perfect;  14 
in  traces.  Twins  :  twinning-plane  /,  sometimes 
consisting  of  five  individuals  (see  f.  308,  p.  98) ; 
also  1-i.  Also  globular,  reniform,  and  other 
imitative  shapes — structure  straight  columnar  ; 
often  massive,  columnar,  or  granular. 

H.=6-6'5.  G.= 4-678-4-84:7.  Lustre  metallic.  Color  pale  bronze-yel- 
low, sometimes  inclined  to  green  or  gray.  Streak  grayish-  or  brownish- 
black.  Fracture  uneven.  Brittle. 

Comp,,  Var.— FeS2,  like  pyrite = Sulphur  53  -3,  iron  46 '7=100. 

The  varieties  that  have  been  recognized  depend  mainly  on  state  of  crystallization ;  as  the 
Radiated  (Strahlkies) :  Radiated  ;  also  the  simple  crystals,  f'ockscomb  (Kammkieft)  :  Aggre- 
gations of  flattened  crystals  into  crest-like  forms.  Spear  (Speerkies) :  Twin  crystals,  with 
reentering  angles  a  little  like  the  head  of  a  spear  in  form.  Capillary  (Haarkies)  :  In  capil- 
lary crystallizations,  etc. 

Pyr. — Like  pyribe.     Very  liable  to  decomposition  ;  more  so  than  pyrite. 

Diff. — Distinguished  from  pyrite  by  its  paler  color,  especially  marked  on  a  fresh  surface  ; 
by  its  tendency  to  tarnish  ;  by  its  inferior  specific  gravity. 

Obs. — Occurs  near  Carlsbad  in  Bohemia  ;  at  Joachimsthal,  and  in  several  parts  of  Saxony  ; 
in  Derbyshire  ;  near  Alston  Moor  in  Cumberland  ;  near  Tavistock  in  Devonshire,  and  in 
Cornwall. 

At  Warwick,  N.  Y.  Massive  fibrous  varieties  abound  throughout  the  mica  slate  of  New 
England,  particularly  at  Cummington,  Mass.  Occurs  at  Lane's  mine,  in  Monroe,  Conn.  ;  in 
Trumbull ;  at  East  Haddam  ;  at  Haverhill,  N.  H.  ;  Galena,  111. ,  in  stalactites.  In  Canada  in 
Neebing. 

Marcasite  is  employed  in  the  manufacture  of  sulphur,  sulphuric  acid,  and  iron  sulphate, 
though  less  frequently  than  pyrite. 


ARSENOPYRITE,  or  MISPICKEL.    Arsenical  Pyrites.    Arsenikkies,  Germ. 

Orthorhombic.  7 A  1=  111°  53',  0  A 14  -  119°  37' ;  c  :  £':  d  =  1-7588  : 
1-4793:1.  6>Al  =  115°  12',  6>  A  l-£  =  130°  4'.  Cleavage:  /rather 
distinct  ;  0,  faint  traces.  Twins  :  twinning-plane  /,  and  14.  Also  colum- 
nar, straight  and  divergent ;  granular,  or  compact. 

H.=5-5-6.  G.=:6-0-6-4 ;  6-269,  Franconia,  Kenngott.  Lustre  metallic. 
15 


226 


DESCRIPTIVE  MINERALOGY. 


Color  silver- white,  inclining  to  steel-gray.    Streak  dark  gra}Tish-black.    Frac- 
ture uneven.     Brittle. 


443 


444 


445 


Franconia,  N.  H.  Franconia,  N.  H.,  and  Kent,  N.  Y. 


Danaite. 


Comp.,  Var.— FeAsS=FeS2  +  AsS2= Arsenic  46'0,  sulphur  19'6,  iron  34 '4=100.  Part  of 
the  iron  sometimes  replaced  by  cobalt ;  a  little  nickel,  bismuth,  or  silver  are  also  occasionally 
present.  The  cobaltic  variety,  called  danaite  (after  J.  Freeman  Dana),  contains  4-10  p.  c.  of 
cobalt. 

Pyr.,  etc. — In  the  closed  tube  at  first  gives  a  red  sublimate  of  arsenic  sulphide,  then  a 
black  lustrous  sublimate  of  metallic  arsenic.  In  the  open  tube  gives  sulphurous  fumes  and  a 
white  sublimate  of  arsenous  oxide.  B.B.  on  charcoal  gives  the  odor  of  arsenic.  The  varieties 
containing  cobalt  give  a  blue  color  with  borax-glass  when  fused  in  O.F.  with  successive  por- 
tions of  flux  until  all  the  iron  is  oxidized.  Gives  fire  with  steel,  emitting  an  alliaceous  odor. 
Decomposed  by  nitric  acid  with  separation  of  arsenous  oxide  and  sulphur. 

Diff. — Distinguished  by  its  form  from  smaltite.  Leucopyrite  (lollingite)  do  not  give 
decided  sulphur  reactions. 

Obs. — Found  principally  in  crystalline  rocks,  and  its  usual  mineral  associates  are  ores  of 
silver,  lead,  and  tin  ;  pyrite,  chalcopyrite,  and  spalerite.  Occurs  also  in  serpentine. 

Abundant  at  Freiberg ;  at  Reichenstein  in  Silesia ;  at  Schladming ;  Andreasberg ;  Joachims- 
thai  ;  at  Tunaberg  in  Sweden  ;  at  Skutterud  in  Norway  ;  in  Cornwall ;  in  Devonshire  at  the 
Tamar  mines. 

In  New  Hampshire,  in  gneiss,  at  Franconia  (danaite) ;  also  at  Jackson  and  at  Haverhill. 
In  Maine,  at  Blue  Hill,  Corinna,  etc.  In  Vermont,  at  Brookfield,  Waterbury,  and  Stockbridge. 
In  Mass. ,  at  Worcester  and  Sterling.  In  Conn. ,  at  Monroe,  at  Mine  Hill,  Roxbury.  In  New 
Jersey,  at  Franklin.  In  N.York,  massive,  in  Lewis,  Essex  Co.,  near  Edenville,  and  else- 
where in  Orange  Co.;  in  Carmel ;  in  Kent,  Putnam  Co.  In  California,  Nevada  Co.,  Grass 
valley.  In  S.  America,  in  Bolivia  ;  also,  niccoliferous  var.,  between  La  Pas  and  Yungas  in 
Bolivia  (anal,  by  Kroeber). 

LOLLINGITE  is  FeAs2  (= Arsenic  72 '8,  iron  27 -2),  and  LEUCOPYBITE  is  Fe2As3  (= Arsenic 
66 '8,  iron  33 -2).  They  are  both  like  arsenopyrite  in  form.  Found,  the  former  at  Lolling  ; 
Schladming ;  Satersberg.  near  Fossum,  Norway  ;  the  latter  at  Reichenstein  ;  Geyer  (geyerite) 
near  Hiittenberg,  Carinthia. 

GLAUCODOT  (Co,Fe)S2+(Co,Fe)As2,  with  Co  :  Fe=2  :  1  =  Sulphur  19*4,  arsenic  45 -5,  cobalt 
23 '8,  iron  11 '3 =100.  Form  like  arsenopyrite.  Huasco,  Chili;  Hakansbo,  Sweden. 

ALLOCLASITE  R4(As,Bi)7S6,  with  R=Bi,Co,Ni,Fe,Zn.     Orawitza,  Hungary. 


SYLVANITE.    Graphic  Tellurium.     Schrifterz,  Schrift-Tellur,  Germ. 

Moiioclinic.  C  =  55°  21  J',  /A  7=  94°  26',  O  A 14  =  121°  21' ;  c  :  I  : 
d  =  1-7732  :  0-889  :  1,  Kokscharof.  Cleavage :  i4  distinct.  Also  massive  ; 
imperfectly  columnar  to  granular. 

II. =1  5-2.  G.  =  7 '99-8 '33.  Lustre  metallic.  Streak  and  color  pure  steel- 
gray  to  silver-white,  and  sometimes  nearly  brass-yellow.  Fracture  uneven. 

Comp.,  Var.— (Ag,Au)Te3  =  (if  Ag  :  Au=l  :  1)  Tellurium  55 '8,  gold  28-5,  silver  15-7=100. 
Antimony  sometimes  replaces  part  of  the  tellurium,  and  lead  part  of  the  other  metals. 


STJLPHARSENITES,    SULPHANTIMONTTES,   ETC.  227 

Pyr.,  etc. — In  the  open  tube  gives  a  white  sublimate  which  near  the  assay  is  gray  ;  when 
treated  with  the  blowpipe  flame  the  sublimate  fuses  to  clear  transparent  drops.  *  B.B.  on 
charcoal  fuses  to  a  dark  gray  globule,  covering  the  coal  with  a  white  coating,  which  treated 
in  R.  F.  disappears,  giving  a  bluish-green  color  to  the  flame ;  after  long  blowing  a  yellow, 
malleable  metallic  globule  is  obtained.  Most  varieties  give  a  faint  coating  of  the  oxides  of 
lead  and  antimony  on  charcoal. 

Obs. —  Occurs  at  Offenbanya  and  Nagyag  in  Transylvania.  In  California,  Calaveras  Co.,  at 
the  Melones  and  Stanislaus  mines ;  Red  Cloud  mine,  Colorado. 

Nam«d  from  Transylvania,  the  country  in  which  it  occurs,  and  in  allusion  to  sylvanium,  one 
of  the  names  at  first  proposed  for  the  metal  tellurium.  Called  graphic  because  of  a  resem- 
blance in  the  arrangement  of  the  crystals  to  writing  characters. 

Schrauf  has  stated  that,  according  to  his  measurements,  sylvanite  is  orthorhombic. 

CALAVERITE  (Genth.}  has  the  composition  AuTe4= Tellurium  55 '5,  gold  44'5=100.  Mas- 
sive. Color  bronze-yellow.  Stanislaus  mine,  Cal.  ;  Red  Cloud  mine,  Colorado. 

NAGYAGITE.    Blattererz,  Blattertellur,  Germ. 

Tetragonal.     0  A  l-i  =  127°  37' ;  c  —  1-298.     O  A  1  =  118°  37'.     Cleav- 
age: basal.     Also  granularly  massive,  particles  of 
various  sizes ;  generally  foliated.  446 

H.=:l-l-5.  G.=6-S5-7'2.  Lustre  metallic,  splen- 
dent. Streak  and  color  blackish  lead-gray.  Opaque. 
Sectile.  Flexible  in  thin  laminae. 

Comp. — Uncertain,  perhaps  R(S,Te)2,  withR=Pb,Au  (Ramm.).  Analysis,  Schonlein,  Te 
30-52,  S  8-07,  Pb  50-78,  Au  9'11,  Ag  0'53,  Cu  0'99=100. 

Pyr.,  etc, — In  the  open  tube  gives,  near  the  assay,  a  grayish  sublimate  of  antimonate  and 
tellurate,  with  perhaps  some  sulphate  of  lead  ;  farther  up  the  tube  the  sublimate  consists  of 
antimonous  oxide,  which  volatilizes  when  treated  with  the  flame,  and  tellurous  oxide,  which 
at  a  high  temperature  fuses  into  colorless  drops.  B.B.  on  charcoal  forms  two  coatings  :  one 
white  and  volatile,  consisting  of  a  mixture  of  antimonite,  tellurite,  and  sulphate  of  lead ;  and 
the  other  yellow,  less  volatile,  of  oxide  of  lead  quite  near  the  assay.  If  the  mineral  is  treated 
for  some  time  in  O.  F.  a  malleable  globule  of  gold  remains  ;  this  cupelled  with  a  little  assay 
lead  assumes  a  pure  gold  color.  Decomposed  by  nitro-hydrochloric  acid. 

Obs. — At  Nagyag  and  Offenbanya  in  Transylvania,  in  foliated  masses  and  crystalline  plates. 

COVELLITB  (Kupferindig,  Germ.). — Composition  CuS= Sulphur  33 -5,  copper  66'5  =  100. 
Hexagonal.  Commonly  massive.  Color  indigo-blue.  Mansfeld,  etc.  ;  Vesuvius,  on  lava ; 
Chili. 

MELONITE  (Genth.).-A  nickel  telluride,  formula  probably  Ni2Te3=tellurium  76 '5,  nickel 
23-5=100.  Hexagonal.  Cleavage  basal  eminent.  Color  reddish- white.  Streak  dark-gray. 
Occurs  mixed  with  other  tellurium  minerals  at  the  Stanislaus  mine,  Cal. 


3.  TERNAEY    COMPOUNDS.     SEJLPHARSENITES,   SULPHANTIMONITES, 

S  ULPHOBISMUTHIT  ES.  * 

(a)  GROUP  I.     Formula  E(ASjSb)2S4=RS4-(As,Sb)2S3. 

MIARGYRITE. 

Monoclinic.  O=  48°  14';  /A  1=  106°  31',  O  A  14  =  136°  8' ;  c  :  I  :  d 
—  1-2883  :  0-9991  :  1,  JN"aumann.  Crystals  thick  tabular,  or  stout,  or  short 
prismatic,  pyramidal.  Lateral  planes  deeply  striated.  Cleavage  :  %-i,  \-i 
imperfect. 

*  The  species  of  this  group  contain  as  bases  chiefly  copper,  lead,  and  silver.  They  can  be 
most  readily  distinguished  by  their  behavior  before  the  blowpipe.  Attention  may  be  called 
to  the  group  of  lead  sulphantimonites,  zinken-tte,  plagio?iite,  (jamesonite)  b&ulangerite,  mene- 
yhinite,  geocronir,e,  for  which  the  pyrognostics  are  nearly  similar,  and  which  are  most  surely 
distinguished  by  their  specific  gravity. 


228  DESCRIPTIVE   MINERALOGY. 

H.=2— 2*5.  G.=5*2-5'4.  Lustre  submetallic-adamantine.  Color  iron- 
black.  Streak  dark  cherry-red.  Opaque,  except  in  thin  splinters,  which, 
by  transmitted  light,  are  deep  blood-red.  Fracture  subconchoidal. 

Comp AgSbS2  (or  Ag2S+Sb2S3)= Sulphur  21 '8,  antimony  41-5,  silver  36 '7=100. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  fuses  easily,  and  gives  a  sublimate  of  antimony 
sulphide ;  in  the  open  tube  sulphurous  and  antimonoue  fumes,  the  latter  as  a  white  sublimate. 
B.B.  on  charcoal  fuses  quietly,  with  emission  of  sulphur  and  antimony  fumes,  to  a  gray  bead, 
which  after  continued  treatment  in  O.F.  leaves  a  bright  globule  of  silver.  If  the  silver  globule 
be  treated  with  phosphorus  salt  in  O.  F. ,  the  green  glass  thus  obtained  shows  traces  of  copper 
when  fused  with  tin  in  R.  F. 

Decomposed  by  nitric  acid,  with  separation  of  sulphur  and  antimonous  oxide. 

Obs. — At  Braiinsdorf ,  near  Freiberg  in  Saxony ;  Felsobanya  (kenngottite) ;  Przibram  in 
Bohemia ;  Clausthal  (hy par gy rite)  ;  Guadalajara  in  Spain  ;  at  Parenos,  and  the  mine  Sta.  M. 
de  Catorce,  near  Potosi ;  also  at  Molinares,  Mexico. 

SARTORITE.    SCLBROCLASE. 

Orthorhombic.     7  A 1=  123°  21',  0  A  14  =  131°  3' ;  c  :  I :  a  =  1-1483  : 

1'8553  :  1.   Crystals  slender.    Cleavage : 
447  O  quite  distinct. 

H.=3.  G.  =  5-393.  Lustre  metallic. 
Color  dark  lead-gray.  Streak  reddish- 
brown.  Opaque.  Brittle. 

Comp.— PbAs2S4(PbS+As2S3)=Sulphur  26 '4, 
arsenic  30  "9,  lead  42-7=100. 

Pyr.,  etc. — Nearly  the  same  as  for  dufrenoy- 
site  (q.  v.),  but  differing  in  strong  decrepitation. 
Obs.— From  the  Binnen  valley  with  dufrenoy- 
site  and  binnite.      As  the  name   Scleroclase  is 
inapplicable,    and    the    mineral    was    first    an- 
nounced by  Sartorius  v.  Waltershausen,  the  species  may  be  appropriately  called  Sartorite. 
It  is  the  binnite  of  Heusser. 

ZINKENITE. 

Orthorhombic.  /A  1=  120°  39',  Rose.  Usual  in  twins,  as  hexagonal 
prisms,  with  a  low  hexagonal  pyramid  at  summit.  Lateral  faces  longitudi- 
nally striated.  Sometimes  columnar,  fibrous,  or  massive.  Cleavage  not 
distinct. 

H.  =  3-3-5.  G.=5'30-5'35.  Lustre  metallic.  Color  and  streak  steel- 
gray.  Opaque.  Fracture  slightly  uneven. 

Comp.— PbSb2S4  (or  PbS  +  Sb2S3)  = Sulphur  22'1,  antimony  42'2,  lead  35 -7=100. 

Pyr.,  etc. — Decrepitates  and  fuses  very  easily  ;  in  the  closed  tube  gives  a  faint  sublimate 
of  sulphur  and  antimonous  sulphide  ;  in  the  open  tube  sulphurous  fumes  and  a  white  subli- 
mate of  oxide  of  antimony.  B.  B.  on  charcoal  is  almost  entirely  volatilized,  giving  a  coating 
which  on  the  outer  edge  is  white,  and  near  the  assay  dark-yellow ;  with  soda  in  R.  F.  yields 
globules  of  lead. 

Soluble  in  hot  hydrochloric  acid  with  evolution  of  sulphuretted  hydrogen  and  separation  of 
lead  chloride  on  cooling. 

Resembles  stibnite  and  bournonite,  but  may  be  distinguished  by  its  superior  hardness  and 
specific  gravity. 

Obs. — Occurs  at  Wolfsberg  in  the  Harz. 

CHALCOSTIBITE  (Kupferantimonglanz,  Germ.). — Composition  CuSbS2  (or  Cu2S  f  Sb2S3)= 
Sulphur  25 '7,  antimony  48 '9,  copper  25-4.  Color  lead -gray  to  iron-gray.  Wolfsberg  in  the 
Harz. 

EMPLECTITE  (Kupferwismuthglanz,  Germ.). — Composition  CuBiS2  (or  CujS+BisSs^ Sul- 
phur 191,  bismuth  62'0,  copper  18'9=100.  Color  grayish  to  tin-white.  Schwarzenberg, 
Saxony;  Copiapo,  Chili. 


SULPHARSENITES,    SULPHANTIMONITES,    ETC. 


229 


BERTHIERITE. — Composition  approximately  FeSb2S4  (orFeS+Sb2S3)=Sulphur30-0,  anti- 
mony 57  '0,  iron  18 '0=100.  Color  dark  steel-gray.  Auvergne  ;  Braunsdorf,  Saxony;  Corn- 
wall, etc. ;  San  Antonio,  Cal. 

(b)  SUB-GROUP.     Formula  E3(Afl,Sb,Bi)4S9=3RS  -h 2(As,Sb,Bi)2S3. 

PLAGIONITE. — Composition  (Rose)  Pb4Sb6S13  (or  4PbS  +  3Sb2S3);=  Sulphur  21-1,  antimony 
37-0,  lead  41 -9.  Monoclinic.  G-.=5'4.  Found  at  Wolfsberg  in  the  Harz. 

JORDANITE  (v.  Rath). — Composition  Pb3As4S9  (or  3PbS+2As2S3)  =  Sulphur  23*8,  arsenic 
24'8,  lead  51*4.  Orthorhombic.  Resembles  sartorite,  but  distinguished  by  its  black  streak, 
its  six-sided  twins,  and  by  not  decrepitating  B.B.  Bihnenthal,  Switzerland. 

BINNITE. — Composition  probably  Cu6As4S9  (or  3Cu2S  +  2As2S3)=:  Sulphur  29'7,  arsenic  31*0, 
copper  39-3—100.  Isometric.  Streak  cherry-red.  Binnenthal  in  dolomite  (dufrenoysite  of 
v.  Walter shausen). 

KLAPROTHOLITE  (Peterseri).  —  Composition  Cu6Bi4Sb9  (or  3Cu2S-t-2Bi2S3).  Orthorhombic. 
Cleavage  i-l  distinct.  Color  steel-gray.  G.=4-6.  Wittichen,  Baden. 

SCHIRMERITE  ( Gentii) .—Composition  R3Bi4S9  (or  3RS  +  2Bi2S3),  with  R=Ag2  :  Pb— 2  :  1. 
This  requires  sulphur  16'4,  bismuth  47'3,  silver  24 '5,  lead  11  '8=100.  Massive,  disseminated 
in  quartz.  Color  lead-gray.  Red  Cloud  mine,  Colorado. 

(c)  GROUP  II.     Formula   E2(Sb,As)2S5=2KS-f  (Sb,As)2S3. 

JAMESONITE.    Federerz,  Germ. 

Orthorhombic.  7  A  7=  101°  20'  and  78°  40'.  Cleavage  basal,  highly 
perfect;  7 and  i-i  less  perfect.  Usually  in  acicular  crystals.  Also  fibrous 
massive,  parallel  or  divergent;  also  in  capillary  forms;  also  amorphous 
massive. 

H.=2-3.  G.=5-5-5-8.  Color  steel-gray  to  dark  lead-gray.  Streak 
gray. 

Comp.— Pb2Sb2S5  (or  2PbS  +  Sb2S3) ;  more  strictly  2PbS=2  (or  Pb,Fe)S.  If  Fe  :  Pb=l  : 
4,  Sulphur  21-1,  antimony  32 '2,  lead  43'7,  iron  3'0— 100.  Small  quantities  of  zinc,  bis- 
muth, silver,  and  copper  are  also  sometimes  present. 

Pyr. — Same  as  for  zinkenite. 

Diff. — Distinguished  from  other  related  species  by  its  perfect  basal  cleavage. 

Obs. — Jamesonite  occurs  principally  in  Cornwall,  in  Siberia,  Hungary,  at  Valentia,  d' Alcan- 
tara in  Spain,  and  Brazil. 

The  feather  ore  occurs  at  Wolfsberg  in  the  Eastern  Harz  ;  also  at  Andreasberg  and  Claus- 
thal ;  at  Freiberg  and  Schemnitz  ;  at  Pf affenberg  and  Meiseberg ;  in  Tuscany,  near  Bottino  ; 
at  Chonta  in  Peru. 


DUFRENOYSITE. 

Orthorhombic.     I /\  I—  93°  39',  O  A  14  =  121°  30',  c  :  b  :  a  =  1-6318  : 
1-0658  :  1.     Usual   in   thick   rectan- 
gular tables.     Cleavage:   O  perfect.  448 
Also  massive. 

H.^3.  G.=5-549-5;569.  Lustre 
metallic.  Color  blackish  lead-gray. 
Streak  reddish-brown.  Opaque.  Brit- 
tle. 

Comp.— Pb2As2S5  (or  2PbS+2As2Ss)=Sul- 
phur  22-10,  arsenic  20'72,  lead  57-18=100. 

Pyr.,  etc. — Easily  fuses  and  gives  a  subli- 
mate of  sulphur  and  arsenous  sulphide ;  in 
the  open  tube  a  smell  of  sulphur  only,  with  a  sublimate  of  sulphur  in  upper  part  of  tube,  and 


230 


DESCRIPTIVE   MINERALOGY. 


of  arsenous  oxide  below.  On  charcoal  decrepitates,  melts,  yields  fumes  of  arsenic  and  a 
globule  of  lead,  which  on  cupellation  yields  silver. 

Obs. — From  the  Binnenthal  in  the  Alps,  in  crystalline  dolomite,  along  with  sartorite,  Jordan  - 
ite,  binnite,  etc. 

Damour,  who  first  studied  the  arsenic-sulphides  of  the  Binnenthal,  analyzed  the  massive 
ore  and  named  it  dufrenoysite.  He  inferred  that  the  crystallization  was  isometric  from  some 
associated  crystals,  and  so  published  it.  This  led  von  Waltershausen  and  Heusser  to  call  the 
isometric  mineral  dufrenoysite,  and  the  latter  to  na-ne  the  orthorhombic  species  binnite.  Von 
Waltershausen,  after  studying  the  prismatic  mineral,  made  out  of  the  species  arsenomelan  and 
sderodase,  yet  partly  on  hypothetical  grounds.  Recently  it  has  been  found  that  three  ortho- 
rhombic  minerals  exist  at  the  locality,  as  announced  by  vom  Rath,  who  identifies  one,  by  speci- 
fic gravity  and  composition,  with  Damour's  dufrenoysite ;  another  he  makes  sderodase  of  von 
"Waltershausen  (sartorite,  p.  228)  ;  and  the  other  he  names  jordanite  (p.  229).  The  isometric 
mineral  was  called  binnite  by  DesCloizeaux. 


FREIESLEBENITE.     Schilfglaserz,  Germ. 

Monoclinic.  C  =  87°  46',  /A  7=  119°  12',  0  A  14  =  137°  10'  (B.  &  M.) ; 
c:t>:d  =  1-5802  :  1-7032  :  1.  O  A  1-4  =  123°  55'. 
Prisms  longitudinally  striated.  Cleavage  :  /  perfect. 
H.  =  2-2-5.  G.  =  6-6-4.  Lustre  metallic.  Color  and 
streak  light  steel-gray,  inclining  to  silver-white,  also 
blackish  lead-gray.  Yields  easily  to  the  knife,  and  is 
rather  brittle.  Fracture  subconchoidal — uneven. 


Comp.— PbaAgaSbsSe,  Ramm.  (or  7RS  +  3Sb2S3,  with7RS=4PbS 
+3 Ag2S)  =  Sulphur  18 "8,  antimony  26 '9,  Iead30'5,  silver  23-8=100. 
Pyr. — In  the  open  tube  gives  sulphurous  and  antimonial  fumes, 
the  latter  condensing  as  a  white  sublimate.  B.  B.  on  charcoal  fuses 
easily,  giving  a  coating  on  the  outer  edge  white,  from  antimonous 
oxide,  and  near  the  assay  yellow,  from  oxide  of  lead ;  continued 
blowing  leaves  a  globule  of  silver. 

Obs.— Occurs  at  Freiberg  in  Saxony  and  Kapnikin  Transylvania;  at 
Ratieborzitz ;  at  Przibram  ;  at  Pelsobanya;  at  Hieudelencina  in  Spain. 
According   to   v.   Zepharovich,  the  mineral  from   Przibram  and 

Braunsdorf,  and  part  of  that  from   Freiberg,  while  identical  in  composition  with  freies- 
lebenite,  has  an  orthorhombic  form.     It  is  called  by  him  DIAPIIORITE. 

BRONGNIARDITE. — Composition  Ag2PbSb2S5  (or  PbS+Ag2S  +  Sb2S3)  =  Sulphur  19'4,  anti- 
mony 29-5,  silver  2(5*1,  lead  25'0=100.  Isometric ;  in  octahedrons,  also  massive.  Color  gray- 
ish-black. Mexico. 

COSALITE  (Genth).—  Composition  Pb2Bi2S5  (or  2PbS+Bi2S3)= Sulphur  16'1,  bismuth  42'2, 
lead  41-7=100.  Color  lead-gray.  Soft  and  brittle.  Cosala,  Sinalva,  Mexico.  Identical 
(Frenzel)  with  Hermann's  retzbanyite. 

PYROSTILPNITE  (Feuerblende,  Germ.}. — In  delicate  crystals;  color  hyacinth-red.  Con- 
tains 62  3  p.  c.  silver,  also  sulphur  and  antimony.  Freiberg  ;  Andreasberg;  Przibram. 

RITTINGERITE. — In  minute  tabular  crystals.  Color  black.  Streak  orange-yellow.  Con- 
tains sulphur,  antimony,  and  silver.  Joachimsthal. 


(d)  GROUP  III.     Formula  E3(As,Sb)2S6=:3KS  +  (AsJ 


FYRARGYRITE.    Ruby  Silver.     Dark  Red  Silver  Ore.     Dunkles  Rothgiiltigerz,  Germ. 

Rhombohedral.  Opposite  extremities  of  crystals  often  unlike.  R  A  R 
=  108°  42'  (B.  &  M.) ;  O  f\  R  =  137°  42' ;  c  =  0'788.  O  A  I3  =  112°  33X, 
6>A1T  =  100°  14/,  ^A^=144:0  21/.  Cleavage:  R  rather  imperfect. 


SULPHAKSENITES,    SULPHANTIMONITES,    ETC. 


231 


450 


451 


Twins:  composition-face— -J-;  0  or  basal  plane,  as  in   f.  290,  p.  95;   also 
R    and    /.     Also  massive,    structure 
granular,  sometimes  impalpable. 

I-I. =2-2-5.  G.=5-7-5-9.  Lustre 
metallic-adamantine.  Color  black, 
sometimes  approaching  cochineal-red. 
Streak  cochineal-red.  Translucent—- 
opaque. Fracture  conchoidal. 

Comp.  —  AgsSbSj,  (or  3Ag2S+SbaS8)= Sul- 
phur 17-7,  antimony '22 -5,  silver  59-8  =  100. 

Pyr.,  etc. — In  the  closed  tube  fuses  and  gives 
a  reddish  sublimate  of  antimonous  sulphide  ; 
in  the  open  tube  sulphurous  fumes  and  a  white  sublimate  of  antimonous  oxide.  B.B.  on 
charcoal  fuses  with  spirting  to  a  globule,  gives  off  antimonous  sulphide,  coats  the  coal  white, 
and  the  assay  is  converted  into  silver  sulphide,  which,  treated  in  O.F.,  or  with  soda  in  R.F., 
gives  a  globule  of  fine  silver.  In  case  arsenic  is  present  it  may  be  detected  by  fusing  the 
pulverized  mineral  with  soda  on  charcoal  in  R.F. 

Decomposed  by  nitric  acid  with  separation  of  sulphur  and  antimonous  oxide. 

Obs. — Occurs  principally  with  calcite,  native  arsenic  and  galenite,  at  Andreasberg ;  also  in 
Saxony,  Hungary,  Norway,  at  Gaudalcanal  in  Spain,  and  in  Cornwall.  In  Mexico  abundant. 
In  Chili ;  in  Nevada,  at  Washoe  in  Daney  Mine ;  abundant  about  Austin,  Eeese  river ;  at 
Poor  Man  lode,  Idaho. 


PROUSTITE.    Light  Red  Silver  Ore.     Lichtes  Rothgiiltigerz,  Germ. 


Ehombohedral.  R  A  R  =  107°  48',  O  A  72  =  137°  9';  c  =  0-78506. 
Also  granular  massive. 

H.  =  2— 2*5.  G.  =  5'422-5'56.  Lustre  adamantine.  Color  cochineal-red. 
Streak  cochineal-red,  sometimes  inclined  to  aurora-red.  Subtransparent — 
subtranslucent.  Fracture  conchoidal — uneven. 


Comp.-Ag3AsS3  (or  3Ag2S+As2S3)  =  Sulphur  19-4,  arsenic  15'1,  silver  65-5=100. 

Pyr.,  etc. — In  the  closed  tube  fuses  easily,  and  gives  a  faint  sublimate  of  arseuous  sulphide ; 
in  the  open  tube  sulphurous  fumes  and  a  white  crystalline  sublimate  of  arsenous  oxide.  B.B. 
on  charcoal  fuses 'and  emits  odors  of  sulphur  and  arsenic  ;  by  prolonged  heating  in  O.F.,  or 
with  soda  in  R.  F. ,  gives  a  globule  of  pure  silver.  Some  varieties  contain  antimony. 

Decomposed  by  nitric  acid,  with  separation  of  sulphur  and  arsenous  oxide. 

Obs. — Occurs  at  Freiberg  and  elsewhere  in  Saxony  ;  at  Joachimsthal  ;  Wolfach  in  Baden ; 
Chalanches  in  Dauphine  ;  Guadalcanal  in  Spain  ;  in  Mexico :  Peru  ;  Chili,  at  Chanarcillo,  in 
magnificent  crystals.  In  Nevada,  in  the  Daney  mine,  and  in  Comstock  lode,  but  rare ;  in 
veins  about  Austin,  Lander  Co.  ;  in  mioroscopic  crystals  in  Cabarrus  Co.,  N.  C.,  at  the 
McMakin  mine  ;  in  Idaho,  at  the  Poor  Man  lode. 


BOURNONITE.    Radelerz,  Germ.  (= Wheel  Ore  . 


Orthorhombic.  7  A  7  =  93°  40',  O  A  l-l  =  136°  IT  (Miller/ ;  c  :  I  :  d  = 
0-95618  :  1-0662  :  1.  O  A  1-2  =  133°  26',  O  A  1  =  127°  20',  O  A  14  =  138° 
t>'.  Cleavage  :  i-l  imperfect  ;  i-l  and  0  less  distinct.  Twins :  twiiming- 
plaue  face  Ij  crystals  often  cruciform  (f.  453),  crossing  at  angles  of  9  ° 
40'  and  86°  20' ;  hence,  also,  cog-wheel  shaped.  Also  massive  ;  granular, 
compact. 


232 


DESCRIPTIVE   MINEKALOGY. 


H.— 2-5-3.  G.  — 5*7-5-9.  Lustre  metallic.  Color  and  streak  steel-gray, 
inclining  to  blackish  lead-gray  or  iron-black.  Opaque.  Fracture  con- 
choidal  or  uneven.  Brittle. 


452 


Oomp.,  Var.— CuPbSbS3  Ramm.  (or  3RS+Sb2S3,  with  3RS=2PbS+Cu2S)= Sulphur  19'6, 
antimony  25 '0,  lead  42-4,  copper  13-0=100. 

Pyr.,  etc — In  the  closed  tube  decrepitates,  and  gives  a  dark-red  sublimate.  In  the  open 
tube  gives  sulphurous  oxide,  and  a  white  sublimate  of  antimonous  oxide.  B.B.  on  charcoal 
fuses  easily,  and  at  first  coats  the  soal  white,  from  antimonous  oxide  ;  continued  blowing 
gives  a  yellow  coating  of  lead  oxide;  the  residue,  treated  with  soda  in  R.F.,  gives  a  globule 
of  copper. 

Decomposed  by  nitric  acid,  affording  a  blue  solution,  and  leaving  a  residue  of  sulphur,  and 
a  white  powder  containing  antim  my  and  lead. 

Obs. — Occurs  in  the  Harz  ;  at  Kapnik  in  Transylvania  ;  at  Servoz  in  Piedmont ;  Brauns- 
dorf  and  Gersdorf  in  Saxony,  Olsa  in  Corinthia,  etc. ;  in  Cornwall ;  in  Mexico ;  at  Huasco- 
Alto  in  Chili  ;  at  Machacamarca  in  Bolivia  ;  in  Peru. 

STYLOTYPITE. — An  iron-silver-copper  bournonite  ;  Copiapo,  Chili. 


BOULANGERITE. 

In  plumose  masses,  exhibiting  in  the  fracture  a  crystalline  structure ; 
also  granular  and  compact. 

H.=: 2-5-3.  G.= 5.75-6*0.  Lustre  metallic.  Color  bluish  lead-gray; 
often  covered  with  yellow  spots  from  oxidation. 


Comp.— Pb8Sb2S6  (or  3PbS4-Sb2S3)=Sulphur  18'2,  antimony  23'1,  lead  58 '7=100. 

Pyr. — Same  as  for  zinkenite. 

Obs.— Quite  abundant  at  Molieres,  department  of  Gard,  in  France  ;  also  found  at  Nasaf  jeld 
in  Lapland  ;  at  Nertschinsk :  Ober-Lahr  in  Sayn-Altenkirchen ;  Wolfsberg  in  the  Harz ;  near 
Bottino  in  Tuscany. 

EPIBOULANGERITE. — Probably  a  decomposition  product  of  boulangerite  (Websky) ;  it  con- 
tains more  sulphur  and  less  antimony.  Altenberg,  Silesia. 

WITTICHENITE. — Composition  Cu3BiS3  (or  3Cu2S+Bi2S3)  =  Sulphur  19'4,  bismuth  42.1, 
copper  38-5  =  100.  Color  steel-gray.  Wittichen,  Baden. 

KOBELLITE.— Pb3BiSbS6  (or  3PbS  +  (Bi.Sb)aS3)  Ramm.  =  Sulphur  16-8,  antimony  107,  bis- 
muth 18 '2,  lead  54-3  =  100.  Color  lead -gray  to  steel-gray.  Hvena,  Sweden. 

AIKINITE  (Nadelerz,  Germ.).—  CuPbBiS3  (or  Cu2S+2PbS+Bi2S3)  =  Sulphur  167,  bismuth 
36-2,  lead  36 '0,  copper  111  =  100.  In  acicular  crystals,  also  massive.  Color  blackish  lead- 
gray.  Beresof,  Urals  ;  Gold  Hill,  North  Carolina. 


SULPHAKSENITEB,   SULPHANTIMONITES,   ETC. 


233 


(e)  GROUP  IY.     Formula  K4(As,Sb,Bi)2S7=4RS  +  (As,Sb,Bi)2S3. 

TETRAHEDRITE.    Gray  Copper  Ore.     Fahlerz ;  Antimon-  and  Quecksilberfahlerz,  Germ, 

Isometric ;  tetrahedral.  Twins :  twinning-plane  octahedral,  producing, 
when  the  composition  is  repeated,  the  form  in  f.  456.  Also  massive ;  gran- 
ular, coarse,  or  fine ;  compact  or  crypto-crystalline 


454 


456 


H.=3-4-5.  G.=4-5-5-ll.  Lustre  metallic.  Color  between  light  flint- 
gray  and  iron-black.  Streak  generally  same  as  the  color;  sometimes 
inclined  to  brown  and  cherry-red.  Opaque ;  sometimes  subtranslticent  in 
very  thin  splinters,  transmitted  color  cherry-red.  Fracture  subconchoidal 
— uneven.  Rather  brittle. 

Oomp.,  Var.— Cu8Sb2S7  (or  4Cu2S  +  Sb2S3),  with,  part  of  the  copper  (Cu2)  often  replaced  by 
iron  (Fe),  zinc  (Zn),  silver  (Ag2),  or  quicksilver  (Hg),  and  rarely  cobalt  (Co),  and  part  of  the 
antimony  by  arsenic,  and  rarely  bismuth.  Ratio  Ag2+Cu2  :  Zn+Fe  generally  =2:1.  There 
are  thus : 

A.  An  antimonial  series;  B.  An  arsenio-antimonial  series;  C.  A  bismuthic  arsenio-anti- 
monial ;  besides  an  arsenical,  in  which  arsenic  replaces  all  the  antimony,  and  which  is  made 
into  a  distinct  species  named  tennantite. 

Var.  1.    Ordinary.  Containing  little  or  no  silver.  Color  steel-gray  to  dark-gray.  Gr.  =5-5'8. 

2.  Argentiferous;  Freibergite.    Light  steel-gray,  sometimes  iron-black.    G.  =4-8-5,  or  less. 

3.  Mei^curiferous  ;  Schwatzite.     Color  gray  to  iron-black.     G.=5-5'6. 
The  following  analyses  will  serve  as  examples  of  these  varieties  : 


S         Sb  As  Cu  Fe 

(1)  Miisen          25-46  1915  4 -93  39 '88  3 '43 

(2)  Meiseberg    24  "80  25 '56  30 '47  3 '52 

(3)  Kotterbach  22 '53  19  "34  2-94  35 '34  0'87 


Zn      Ag 

3  -50    0-60  Ni  Co  1  -64=98  "59  Rammelsberg. 
3-39  10.48  Pb  0-78 =100 -00  " 

0-69    Hg  17-27,  Pb  0'21  Bi  0'81=100 

v.  Rath. 


Pyr.,  etc. — Differ  in  the  different  varieties.  In  the  closed  tube  all  fuse  and  give  a  dark- 
red  sublimate  of  antimonous  sulphide  ;  when  containing  mercury,  a  faint  dark-gray  sublimate 
appears  at  a  low  red  heat ;  and  if  much  arsenic,  a  sublimate  of  arsenous  sulphide  first  forms. 
In  the  open  tube  fuses,  gives  sulphurous  fumes  and  a  white  sublimate  of  antimony  ;  if 
arsenic  is  present  a  crystalline  volatile  sublimate  condenses  with  the  antimony ;  if  the 
ore  contains  mercury  it  condenses  in  the  tube  in  minute  metallic  globules.  B.B.  on  charcoal 
fuses,  gives  a  coating  of  antimonous  oxide  and  sometimes  arsenous  acid,  zinc  oxide,  and  lead 
oxide  ;  the  arsenic  may  be  detected  by  the  odor  when  the  coating  is  treated  in  R.F.  ;  the 
zinc  oxide  assumes  a  green  color  when  heated  with  cobalt  solution.  The  roasted  mineral 
gives  with  the  fluxes  reactions  for  iron  and  copper ;  with  soda  yields  a  globule  of  metallic 
copper.  To  determine  the  presence  of  a  trace  of  arsenic  by  the  odor,  it  is  best  to  fuse  the 
mineral  on  charcoal  with  soda.  The  presence  of  mercury  is  best  ascertained  by  fusing  the 


234:  DESCRIPTIVE   MINERALOGY. 

pulverized  ore  in  a  closed  tube  with  about  three  times  its  weight  of  dry  soda,  the  metal 
subliming  and  condensing  in  minute  globules.  The  silver  is  determined  by  cupellation. 

Decomposed  by  nitric  acid,  with  separation  of  sulphur,  and  antimonous  and  arsenous  oxides. 

Obs. — The  Cornish  mines,  near  St.  Aust.  ;  at  Andreasberg  and  Clausthal  in  the  Harz  ; 
Kremnitz  in  Hungary ;  Freiberg  in  Saxony  ;  Przibram  in  Bohemia  ;  Kahl  in  Spessart ;  Kap- 
nik  in  Transylvania  ;  Dillenburg  in  Nassau  ;  and  other  localities.  The  ore  containing  mer- 
cury occurs  in  Schmolnitz,  Hungary  ;  at  Schwatz  in  the  Tyrol ;  and  in  the  valleys  of  Angina 
and  Costello  in  Tuscany. 

Found  in  Mexico,  at  Durango,  etc.  ;  at  various  mines  in  Chili ;  in  Bolivia ;  at  the  Kellogg 
mines,  Arkansas  ;  at  Newburyport,  Mass.  In  California  in  Mariposa  Co. ;  in  Shasta  Co.  In 
Nevada,  abundant  at  the  Sheba  and  De  Soto  mines,  Humboldt  Co.  ;  near  Austin  in  Lander 
Co.  ;  in  Arizona  at  the  Heintzelman  mine,  containing  1^  p.  c.  of  silver ;  at  the  Sana  Rita  mine. 

RICXNITE  (Brauns). — A  bismuth  tetrahedrite  from  Cremenz,  Einfischthal,  Switzerland. 

MALINOWSKITE. — A  tetrahedrite  containing  9-18  p.  c.  lead,  and  10-13  p.  c.  silver.  District 
of  Rocuay,  Peru.  (5th  Append.  Min.,  Chili.) 


TENNANTITE.    Graukupfererz,  Germ. 

Isometric ;  holohedral,  Phillips.  Cleavage :  dodecaliedral  imperfect. 
Twins  as  in  tetrahedrite.  Massive  forms  unknown. 

H.=3-5-4.  G.=4-37-4-53.  Lustre  metallic.  Color  blackish  lead-gray 
to  iron-black.  Streak  dark  reddish-gray.  Fracture  uneven. 

Comp. — Cu8As2S7  (or  4Cu2S+As2S3),  with  Cu2  replaced  in  part  by  Fe,  Ag2,  etc.,  as  in  tetra- 
hedrite, with  which  it  agrees  in  crystalline  form. 

Pyr. — In  the  closed  tube  gives  a  sublimate  of  arsenous  sulphide.  In  the  open  tube  gives 
sulphurous  fumes,  and  a  sublimate  of  arsenous  oxide.  B.B.  on  charcoal  fuses  with  intumes- 
cence and  emission  of  arsenic  and  sulphur  fumes  to  a  dark-gray  magnetic  globule.  The 
roasted  mineral  gives  reactions  for  copper  and  iron  with  the  fluxes;  with  soda  on  charcoal 
gives  metallic  copper  with  iron. 

Obs. — Found  in  the  Cornish  mines.     Also  at  Skutterud  in  Norway,  and  in  Algeria. 

JULIANITE  (Websky)  is  near  tennantite.     Gr.=5-12.     Rudelstadt,  Silesia. 

MENEGHINITE  has  the  composition  Pb4Sb2S7(4PbS.+  Sb2S3)=Sulphur  17'3,  antimony  16'8, 
lead  63'9=100.  Resembles  boulangerite.  Bottino,  Tuscany  ;  Schwarzenberg,  Saxony. 


(/)  GROUP  Y.     Formula  E5(As,Sb)2S8=5ES+(AsJSb)2S3. 

STEPHANITE.    Sprodglaserz,  Germ. 

Orthorhombic.     1 A  7  =  115°  39',  O  A 14  =  132°  32i' ;  c:l\d  =  1-0897 
:  1-5844:1.     O  Al  =  127°  51',  O  A 1-2  =  145°  34.    Cleav- 
457  age  :  2-#  and  i-l  imperfect.     Twins  :  twinning-plane  // 

XT — -7^  forms  like  those  of  aragonite  frequent.     Also  massive, 

//    I  /  \i\       compact,  and  disseminated. 

L — ,/V^          IL=2-2-5.      G.=6-269,   Przibram.      Lustre   metallic. 
Color  and  streak  iron-black.     Fracture  uneven. 

Comp.— Ag5SbS4  (or  5  Ag2S+Sb2S,)= Sulphur  16'2,  antimony  15'3, 
sUver  68-5=100. 

Pyr.  —In  the  closed  tube  decrepitates,  fuses,  and  after  long  heating 
gives  a  faint  sublimate  of  antimonous  sulphide.  In  the  open  tube  fuses, 
giving  off  antimonial  fumes  and  sulphurous  oxide.  B.B.  on  charcoal 
fuses  with  projection  of  small  particles,  coats  the  coal  with  antimonous 

oxide,  which  after  long  blowing  is  colored  red  from  oxidized  silver,  and  a  globule  of  metallic 
silver  is  obtained. 

Soluble  in  dilute  heated  nitric  acid,  sulphur  and  oxide  of  antimony  being  deposited. 


SULPHA  RSENITES,    SULPHANTIMONITES,    ETC.  235 

Obs. — At  Freiberg  and  elsewhere  in  Saxony ;  at  Przibram  in  Bohemia  ;  in  Hungary  ;  at 
Andreasberg ;  at  Zacatecas  in  Mexico ;  and  in  Peru.  In  Nevada,  an  abundant  silver  ore  in 
the  Comstock  lode  ;  at  Ophir  and  Mexican  mines  in  fine  crystals ;  in  the  Reese  river  and 
Humboldt  and  other  regions.  In  Idaho,  at  the  silver  mines. 

GEOCRONITE. — Composition  PbaSb.Se  ( or 5PbS  +  Sb2S3)  =  Sulphur  16'7,  antimony  15'9,  lead 
67-4=100  (also  contains  a  little  arsenic).  Color  light  lead-gray.  Sala,  Sweden;  Merido, 
Spain  ;  Val  di  Castello,  Tuscany. 


POLYBASITE. 

Orthorhombic,  DesCl.  I/\  I  nearly  120°,  O/\l  =  121°  30'.  Crystals 
usually  short  tabular  prisms,  with  the  bases  triangularly  striated  parallel 
to  alternate  edges.  Cleavage :  basal  imperfect.  Also  massive  and  dis- 
seminated. 

H.  =  2-3.  G.  =  6§214.  Lustre  metallic.  Color  iron-black  ;  in  thin  crys- 
tals cherry-red  by  transmitted  light.  Streak  iron-black.  Opaque  except 
when  quite  thin.  Fracture  uneven. 

Comp. — AggSbSfi  (or  9Ag2S  +  Sb2S'j),  if  containing  silver  without  copper  or  arsenic,  Sulphur 
14 '8,  antimony  9*7,  silver  95  5  =  10U.  But  with  Ag2  replaced  in  part  by  Cua  (ratio  Ag  :  Cu= 
1  :  4  bo  1  :  11),  and  Sb  replaced  by  As  (ratio  1:1,  etc.). 

Pyr.,  etc. — In  the  open  tube  fuses,  gives  sulphurous  and  antimonial  fumes,  the  latter 
forming  a  white  sublimate,  sometimes  mixed  with  crystalline  arsenous  oxide.  B.B.  fuses 
with  spirting  to  a  globule,  gives  off  sulphur  (sometimes  arsenic),  and  coats  the  coal  with  anti- 
monous  oxide  ;  with  long-continued  blowing  some  varieties  give  a  faint  yellowish- white  coat- 
ing of  zinc  oxide,  and  a  metallic  globule,  which  with  salt  of  phosphorus  reacts  for  copper, 
and  cupelled  with  lead  gives  pure  silver. 

Decomposed  by  nitric  acid. 

Obs. — Occurs  in  Mexico  ;  at  Tres  Puntos,  Chili ;  at  Freiberg  and  Przibram.  In  Nevada, 
at  the  Reese  mines  ;  in  Idaho,  at  the  silver  mines  of  the  Owhyhee  district. 

POLYARGYRITE.— Isometric.  Cleavage  cubic.  Malleable.  Comp.  12Ag2S+Sb2S,.  Wol- 
fach,  Baden. 


ENARGITE. 

Orthorhombic.  If\I=  97°  53',  O  A  14  =  136°  37'  (Dauber) ;  c  :  I :  a  — 
0-94510  :  1-1480  :  1.  O  A 1-2  =  140°  20',  O  A  1  =  128°  35'.  Cleavage  :  / 
perfect ;  i-l,  i-l  distinct ;  O  indistinct.  Also  massive,  granular  or  columnar. 

H.=3.  G.=:4-43-4:-4:5  ;  4-362,  Kenngott.  Lustre  metallic.  Color  gray- 
ish to  iron-black  ;  streak  grayish-black,  powder  having  a  metallic  lustre. 
Brittle.  Fracture  uneven. 

Comp. — Cu3AsS 4= Sulphur  32 '5,  arsenic  191,  copper  48 '4= 100,  usually  containing  also  a 
little  antimony,  and  zinc,  and  sometimes  silver. 

Pyr. — In  the  close-"'  tube  decrepitates,  and  gives  a  sublimate  of  sulphur ;  at  a  higher  tem- 
perature fuses,  and  gives  a  sublimate  of  arsenous  sulphide.  In  the  open  tube,  heated  gently, 
the  powdered  mineral  gives  off  sulphurous  and  arsenous  oxides,  the  latter  condensing  to  a 
sublimate  containing  some  antimonous  oxide.  B.B.  on  charcoal  fuses,  and  gives  a  faint  coat- 
ing of  arsenous  oxide,  antimonous  oxide,  and  zinc  oxide  ;  the  roasted  mineral  with  the  fluxea 
gives  a  globule  of  metallic  copper. 

Soluble  in  nitro-hydrochloric  acid. 


236  DESCRIPTIVE   MINERALOGY. 

Obs. — From  Morococha,  Cordilleras  of  Peru  ;  Famatina  Mts. .  Argentine  Republic  ;  from 
Chili;  mines  of  Santa  Anna,  N.  Granada ;  at  Gosihuirachi  in  Mexico  ;  Brewster's  gold  mine, 
Chesterfield  district,  S.  Carolina ;  in  Colorado  ;  at  Willis's  Gulch,  near  Black  Hawk  ;  southern 
Utah ;  Morning  Star  mine,  Cal. 

FAMATINITE  (Stelzner). — An  antimonial  enargite.  Massive.  Color  reddish  gray.  Fama- 
tina Mts. ,  Argentine  Republic  ;  Cerro  de  Pasca,  Peru. 

LUZONITE. — Similar  to  enargite  in  composition,  but  unlike  inform,  according  to  Weisbach. 
Mancayan  Island,  Luzon. 

CLARITE  (Sandberger}. — Also  similar  to  enargite  in  composition,  but  in  form  monoclinic, 
and  having  a  perfect  cleavage  parallel  to  the  clinopinacoid.  Schapbach,  Black  Forest. 

EPIGBNITE.— Composition  S  32-24,  As  12-78,  Cu  4068,  Fe  14 '20=100.  Orthorhombic. 
Color  steel-gray.  Neugliick  mine,  Wittichen. 


COMPOUNDS    OF   CHLORINE,    BKOMINE,    IODINE. 


237 


III.  COMPOUNDS  OF  CHLORINE,  BROMINE,  IODINE. 


1.  ANHYDROUS  CHLORIDES,  ETC. 


HALITE.     COMMON  SALT.     Kochsalz,  Steinsalz,  Germ. 


•ic.     Usually  in  cubes  ;  rarely  in  octahedrons ;  faces  of  crystals 
5  cavernous,  as  in  f.  458.     Cleavage  :  cubic, 


458 


Isometric, 
sometimes 
perfect.     Massive  and  granular,  rarely  columnar. 

H.=2-5.  G-.=2-l-2-257.  Lustre  vitreous.  Streak 
white.  Color  white,  also  sometimes  yellowish,  red- 
dish, bluish,  purplish ;  often  colorless.  Transparent 
— translucent.  Fracture  conchoidal.  Rather  brittle. 
Soluble;  taste  purely  saline. 

Comp. — NaCl= Chlorine  60'7,  sodium  39'3— 100.  Commonly 
mixed  with  some  calcium  sulphate,  calcium  chloride,  and  magne- 
sium chloride,  and  sometimes  magnesium  sulphate,  which  render 
it  liable  to  deliquesce. 

Pyr.,  etc. — In  the  closed  tube  fuses,  often  with  decrepitation ;  when  fused  on  the  platinum 
loop  colors  the  flame  deep  yellow. 

Diff. — Distinguished  by  its  taste,  solubility,  and  perfect  cubic  cleavage. 

Obs. — Common  salt  occurs  in  extensive  but  irregular  beds  in  rocks  of  various  ages,  associ- 
ated with  gypsum,  polyhalite,  calcite,  clay,  and  sandstone ;  also  in  solution,  and  forming 
ialt  springs. 

The  principal  mines  of  Europe  are  at  Wieliczka,  in  Poland;  at  Hall,  in  the  Tyrol;  Stass- 
furt,  in  Prussian  Saxony ;  and  along  the  range  through  Eeichenthal  in  Bavaria,  Hallein  in 
Salzburg,  Hallstadt,  Ischl,  and  Ebensee,  in  upper  Austria,  and  Aussee  in  btyria  ;  in  Transyl- 
vania ;  Wallachia,  Galicia,  and  upper  Silesia  ;  Vic  and  Dieuze  in  France  ;  Valley  of  Cardona 
and  elsewhere  in  Spain,  forming  hills  300  to  400  feet  high  ;  Bex  in  Switzerland  ;  and  North- 
wich  in  Cheshire,  England.  It  also  occurs  near  Lake  Oroomiah,  the  Caspian  Lake. ,  etc.  In 
Algeria  ;  in  Abyssinia  ;  in  India  in  the  province  of  Lahore,  and  in  the  valley  of  Cashmere ; 
in  China  and  Asiatic  Russia  ;  in  South  America,  in  Peru,  and  at  Zipaquera  and  Nemocon. 

In  the  United  States,  salt  has  been  found  forming  beds  with  gypsum,  in  Virginia,  Wash- 
ington Co.  ;  in  the  Salmon  River  Mts.  of  Oregon ;  in  Louisiana.  Brine  springs  are  very 
numerous  in  the  Middle  and  Western  States.  These  springs  are  worked  at  Salina  and  Syra- 
cuse, N.  Y.  ;  in  the  Kanawha  Valley,  Va.  ;  Muskingum,  Ohio ;  Michigan,  at  Saginaw  and 
elsewhere  ;  and  in  Kentucky.  Vast  lakes  of  salt  water  exist  in  many  parts  of  the  world. 
Lake  Timpanogos  in  the  Rocky  Mountains,  4,200  feet  above  the  level  of  the  sea,  now  called 
the  Great  Salt  Lake,  is  2,000  square  miles  in  area.  L.  Gale  found  in  this  water  20*196  per 
cent,  of  sodium  chloride  in  1852  ;  but  the  greater  rainfall  of  the  last  few  years  has  dimin- 
ished the  proportion  of  saline  matter.  The  Dead  and  Caspian  Seas  are  salt,  and  the  waters 
of  the  former  contain  20  to  26  parts  of  solid  matter  in  100  parts. 

HUANTAJAYTTE. — Composition  20NaCl  + AgCl.  Occurs  in  white  cubes  in  the  mine  of  San 
Simon,  Cerro  de  Huantajaya,  Peru. 


238  DESCRIPTIVE   MINERALOGY. 


SYLVITE. 

Isometric.     Cleavage  cubic.     Also  compact. 

H.  =  2.  G.=l-9-2.  White  or  colorless.  Vitreous.  Soluble;  taste  like 
that  of  common  salt. 

Comp. — KC1= Chlorine  47 '65,  potassium  52-35  =  100.     But  often  containing  impurities. 

Pyr.,  etc. — B.B.  in  the  platinum  loop  fuses,  and  gives  a  violet  color  to  the  outer  flame. 
Added  to  a  salt  of  phosphorus  bead,  which  has  been  previously  saturated  with  copper  oxide, 
colors  the  O.F.  deep  azure-blue.  Water  completely  dissolves  it. 

Obs. — Occurs  at  Vesuvius,  about  the  fumaroles  of  the  volcano.  Also  at  Stassfurt ;  at  Leo- 
poldshall  (leopoldite) ;  at  Kalusz,  G-alicia. 

CERARGYRITE.    Kerargyrite.     Hornsilver.    Silberhornerz,  Germ. 

Isometric.  Cleavage  none.  Twins:  twinning-plane  octahedral.  Usually 
massive  and  looking  like  wax ;  sometimes  columnar,  or  bent  columnar ; 
often  in  crusts. 

H.=1-1'5.  Gr.  =  5'552.  Lustre  resinous,  passing  into  adamantine.  Color 
pearl-gray,  grayish-green,  whitish,  rarely  violet-blue,  colorless  sometimes 
when  perfectly  pure ;  brown  or  violet-brown  on  exposure.  Streak  shin- 
ing. Transparent — feebly  subtranslucent.  Fracture  somewhat  conchoidal. 
Sectile. 

Comp.— AgCl= Chlorine  24 '7,  silver  75-3=100. 

Pyr.,  etc. — In  the  closed  tube  fuses  without  decomposition.  B.B.  on  charcoal  gives  a 
globule  of  metallic  silver.  Added  to  a  bead  of  salt  of  phosphorus,  previously  saturated  with 
copper  oxide,  and  heated  in  O.F.,  imparts  an  intense  azure-blue  to  the  flame.  A  fragment 
placed  on  a  strip  of  zinc,  and  moistened  with  a  drop  of  water,  swells  up,  turns  black,  and 
finally  is  entirely  reduced  to  metallic  silver,  which  shows  the  metallic  lustre  on  being  pressed 
with  the  point  of  a  knife.  Insoluble  in  nitric  acid,  but  soluble  in  ammonia. 

Obs. — Occurs  in  veins  of  clay  slate,  accompanying  other  ores  of  silver,  and  usually  only  in 
the  higher  parts  of  these  veins.  It  has  also  been  observed  with  ochreous  varieties  of  brown 
iron  ore  ;  also  with  several  copper  ores,  with  calcite,  barite,  etc. 

The  largest  masses  are  brought  from  Peru,  Chili,  and  Mexico.  Also  occurs  in  Nicaragua 
nearOcotal;  in  Honduras.  It  was  formerly  obtained  in  the  Saxon  mining  districts  of 
Johanngeorgenstadt  and  Freiberg,  but  is  now  rare.  Found  in  the  Altai ;  at  Kongsberg  in 
Norway ;  in  Alsace ;  rarely  in  Cornwall,  and  at  Huelgoet  in  Brittany.  In  Nevada,  about 
Austin,  Lander  Co.,  abundant ;  at  mines  of  Comstock  lode.  In  Arizona,  in  the  Willow  Springs 
dist. ,  veins  of  El  Dorado  canon,  and  San  Francisco  dist.  In  Idaho,  at  the  Poor  Man  lode. 

Named  from  Kf/uaf,  horn,  and  apy^pof,  silver. 

CALOMEL  (Quecksilberhornerz,  Germ.). — Composition  HgCl= Chlorine  15-1,  mercury  84 '9 
=100.  Color  white,  grayish,  brown.  Spain. 

SAL  AMMONIAC  (Salmiak,  Germ.). — Ammonium  chloride,  NH4C1= Ammonium  33-7,  chlo- 
rine 66-3=100.  Vesuvius,  Etna,  and  many  volcanoes. 

NANTOKITB  (Breithaupt). — Composition  CuCl= Chlorine  35 '9,  copper  64 '1=100.  Cleavage 
cubic.  Color  white.  Nantoko,  Chili. 

EMBOLITE. — Ag(Cl,Br)  ;  the  ratio 'of  Cl  :  Br  varying  from  3  :  1  to  1  :  3.  Color  grayish- 
green.  At  various  mines  in  Chili ;  also  Mexico  ;  Honduras. 

BROMYRITE,  Bromargyrite  (Bromsilber,  Germ.).  —  Silver  bromide,  AgBr=Bromine  42  6, 
silver  57-4=100.  Color  when  pure  bright  yellow,  slightly  greenish.  Chili;  Mexico. 

IODYRITE,  lodargyrite  (lodsilber,  Germ.). — Silver  iodide,  Agl  =  Iodine  54'0,  silver  46 '0= 
100.  Color  yellow.  Mexico  ;  Chili ;  Spain  ;  Cerro  Colorado  mine  in  Arizona. 

TOCORNALITE  (Domeyko). — Composition  Agl-t-Hgl.  Amorphous.  Color  pale  yellow. 
Chanarcillo,  Chili. 

CHLOROCALCITE  (Scacchi). — From  Vesuvius,  contained  58 '76  p.  c.  CaCl2 ;  with  also  KC1, 
NaCl,MgCl2.  CHLORALLTJMINITE,  CIILORMAGNESITE,  and  CIILOROTHIONITE  are  also  frcm 
Vesuvius. 


COMPOUNDS    OF   CHLORINE,   BROMINE,   IODINE.  239 

COTTJNNITE.—  Lead  chloride,  PbCl2= Chlorine  25 '5,  lead  74 '5=100.     Soft.    White.    Vesu- 
vius.    PSEUDOCOTUNNITE  (Scacchi),  Vesuvius. 


MOLYSITE. — Composition  FeCl6= Chlorine  65-5,  iron  34-5=100.     Vesuvius. 


2.   HYDROUS    CHLOEIDES. 


CARNALLITE. 

Massive,  granular ;  flat  planes  developed  by  action  of  water,  but  no  dis- 
tinct traces"  of  cleavage ;  lines  of  striae  sometimes  distinguished,  which 
indicate  twin- com  position. 

Lustre  shining,  greasy.  Color  milk-white,  but  often  reddish  from  mix- 
ture of  oxide  of  iron.  Fracture  conchoidal.  Soluble.  Strongly  phosphor 
escent. 

Comp. — KMgCl3.6aq=KCl+MgCl2  +  6aq=Magnesiurn  chloride  34 -2,  potassium  chloride 
26-9,  water  38 -9  =  100. 

The  brown  and  red  color  of  the  mineral  is  due. partly  to  iron  sesqui oxide,  which  is  in  hex- 
agonal tables,  and  partly  to  organic  matters  (water-plants,  infusoria,  sponges,  etc.). 

Pyr.,  etc. — B.B.  fuses  easily.  Soluble  in  water,  100  parts  of  water  at  18'75J  C.  taking  up 
64-5  parts. 

Obs. — Occurs  at  Stassfurt,  where  it  forms  beds  in  the  upper  part  of  the  salt  formation, 
alternating  with  thinner  beds  of  common  salt  and  kieserite,  and  also  mixed  with  the  common 
salt.  Its  beds  consist  of  subordinate  beds  of  different  colors,  reddish,  bluish,  brown,  deep  red, 
sometimes  colorless.  Sylvite  occurs  in  the  carnallite.  Also  found  at  Westeregeln  ;  with  salt 
at  Maman  in  Persia.  Its  richness  in  potassium  makes  it  valuable  for  exploration. 

TACHIIYDRITE. — Composition  CaMg2Cl6  +  12aq=CaCl2  +  2MgCl2  +  12aq  (Ramm. )  =  Chlorine 
40'3,  magnesium  9'5,  calcium  7'5,  water  42'7=100.  Color  yellowish.  Deliquescent.  Stass- 
furt. 

KREMERSITE.— Probably  2NH4Cl+2KCl-j-FeCl6+3aq.     Vesuvius. 

ERYTHROSIDERITE,  also  from  Vesuvius,  is  2KCl+FeCle+2aq. 


3.  OXYCHLOKIDES. 

ATACAMITE. 

Orthorhombic.  I A  1=  112°  20',  O  A  14  =  131°  29' ;  c  :  I  :  a  =  1-131 
:  1'492  :  1.  Usually  in  modified  rectangular  prisms,  vertically  striated  ;  also 
in  rectangular  octahedrons.  Twins :  twinning-plane  /;  consisting  of 
three  individuals.  Cleavage:  i-%  perfect,  14  imperfect.  Occurs  also  mas- 
sive lamellar. 

II. =3-3-5.  G.= 3-761  (Klein),  3-898  (Zepharovich).  Lustre  adamantine- 
vitreous.  Color  various  shades  of  bright  green,  rather  darker  than  emerald, 
sometimes  blackish-green.  Streak  apple-green.  Translucent — subtraus- 
lucent. 


24:0  DESCRIPTIVE    MINERALOGY. 

,  Oomp.— CuCl2+3H2CuO2— Chlorine  16-64,  copper  59*45,  oxygen  11-25,  water  12'66=100. 
Also  other  compounds  with  more  water  (18  and  22$  p.  c.). 

Pyr.,  etc. — In  the  closed  tube  gives  off  much,  water,  and  forms  a  gray  sublimate.  B.B.  on 
charcoal  fuses,  coloring  the  O.F.  azure-Blue,  with  a  green-  edge,  and  giving  two  coatings, 
one  brownish  and  the  other  grayish-white  ;  continued  blowing  yields  a  globule  of  metallic 
copper  ;  the  coatings  touched  with  the  R.F.  volatilize,  coloring  the  flame  azure-blue.  In  acids 
easily  soluble. 

Obs. — Occurs  in  different  parts  of  Chili ;  in  the  district  of  Tarapaca,  Bolivia ;  at  Tocopilla 
in  Bolivia  ;  with  malachite  in  South  Australia ;  Serro  do  Bembe,  near  Ambriz,  on  the  west 
coast  of  Africa  ;  at  the  Estrella  mine  in  southern  Spain ;  at  St.  Just  in  Cornwall. 

TALLINGITE. — Composition  CuCl2+4H2Cu02+4aq.  In  thin  crusts.  Color  blue.  Botal- 
lack  mine,  Cornwall. 

ATELITE. — Composition  CuCl2-t-2H2CuO3  +  aq.     Formed  from  tenorite.     Yesuvius. 

PERCYLITE. — An  oxychloride  of  lead  and  copper.  Occurs  in  minute  sky-blue  cubes. 
Sonora,  Mexico  ;  So.  Africa. 

MATLOCKITE.— Composition  PbCl2+PbO= Lead  chloride  55 -5,  lead  oxide  44 '5 =100.  Crom- 
ford,  near  Matlock,  Derbyshire. 

MENDIPITE.— Composition  PbCla+2PbO=Lead  chloride  38 '4,  lead  oxide  61 '6=100.  In 
columnar  masses,  often  radiated.  Color  white.  Mendip  Hills,  Somersetshire;  Brillon, 
Westphalia. 

SOHWARTZEMBERGITE. — Composition  Pb(I,Cl)2+2PbO.  Color  yellow.  Desert  of  Ata- 
cama. 

DAUBREITE.— Composition  (Bi203)4BiCl3=Bi203  76-16,  BiCl3  23*84=100.  Amorphous. 
Structure  earthy,  sometimes  fibrous.  Color  yellowish-gray.  H.  =2*5.  G.  =6 '4-6 '5.  From 
the  mine  Constancia,  Cerro  de  Tanza,  Bolivia  (Domeyko). 


FLUORINE   COMPOUNDS. 


241 


IV.  FLUORINE   COMPOUNDS. 


1.  ANHYDEOUS  FLUOKIDES. 


FLUORITE  or  FLUOR  SPAR.     Flusspath,  Germ. 

Isometric;  forms  usually  cubic  (see  f.  39,  40,  41,  52,  55,  etc.,  pp.  16 
to  19).  Cleavage  :  octahedral,  perfect.  Twins  : 
twinning-plane,  1,  f.  266,  p.  91.  Massive. 
Rarely  columnar ;  usually  granular,  coarse  or 
fine.  Crystals  often  having  the  surfaces  made 
up  of  small  cubes,  or  cavernous  with  rectangular 
cavities. 

I-I.=4.  GL  —  3-01-3-25.  Lustre  vitreous  ; 
sometimes  splendent ;  usually  glimmering  in  the 
massive  varieties.  Color  white,  yellow,  green, 
rose,  and  crimson-red,  violet-blue,  sky-blue,  and 
brown :  wine-yellow,  greenish  and  violet-blue, 
most  common  ;  red,  rare.  Streak  white.  Trans- 
parent— subtranslucent.  Brittle.  Fracture  of  fine  massive  varieties  flat- 
conchoidal  and  splintery.  Sometimes  presenting  a  bluish  fluorescence. 
Phosphoresces  when  heated. 

Comp.,  Var. — Calcium  fluoride,  CaF2= Fluorine  48'7,  calcium  51  '3=100.  Berzelius  found 
0-5  of  calcium  phosphate  in  the  fluorite  of  Derbyshire.  The  presence  of  chlorine  was  detected 
early  by  Scheele.  Kersten  found  it  in  fluor  from  Marienberg  and  Freiberg.  The  bright 
colors,  as  shown  by  Kenngott,  are  lost  on  heating  the  mineral ;  they  are  attributed  mainly  to 
different  hydrocarbon  compounds  by  Wyrouboff ,  the  crystallization  having  taken  place  from 
aqueous  solution. 

Var.  Ordinary ;  (a)  cleavable  or  crystallized,  very  various  in  colors;  (b)  coarse  to  fine 
granular  ;  (c)  earthy,  dull,  and  sometimes  very  soft.  A  soft  earthy  variety  from  Ratofka, 
Russia,  of  a  lavender-blue  color,  is  the  ratofkite.  The  finely-colored  fluorites  have  been 
called,  according  to  their  colors,  false  ruby,  topaz,  emerald,  amethyst,  etc.  The  colors  of  the 
phosphorescent  light  are  various,  and  are  independent  of  the  actual  color  ;  and  the  kind 
affording  a  green  color  is  (d)  the  chlorophane. 

Pyr.,  etc, — In  the  closed  tube  decrepitates  and  phosphoresces.  B.B.  in  the  forceps  and 
on  charcoal  fuses,  coloring  the  flame  red,  to  an  enamel  which  reacts  alkaline  to  test  paper. 
With  soda  on  platinum  foil  or  charcoal  fuses  to  a  clear  bead,  becoming  opaque  on  cooling  ; 
with  an  excess  of  soda  on  charcoal  yields  a  residue  of  a  difficultly  fusible  enamel,  while  most 
of  the  soda  sinks  into  the  coal ;  with  gypsum  fuses  to  a  transparent  bead,  becoming  opaque 
on  cooling.  Fused  in  an  open  tube  with  fused  salt  of  phosphorus  gives  the  reaction  for  fluor- 
ine. Treated  with  sulphuric  acid  gives  fumes  of  hydrofluoric  acid  which  etch  glass.  Phos- 

16 


242 


DESCRIPTIVE   MINERALOGY. 


phorescence  is  obtained  from  the  coarsely  powdered  spar  below  a  red  heat.  At  a  high  tem- 
perature it  ceases,  but  is  partially  restored  by  an  electric  discharge. 

DifF. — Recognized  by  its  octahedral  cleavage,  its  etching  power  when  heated  in  the  glass 
tube,  etc. 

Obs. — Sometimes  in  beds,  but  generally  in  veins,  in  gneiss,  mica  slate,  clay  slate,  and  also 
in  limestones,  both  crystalline  and  uncrystalline,  and  sandstones.  Often  occurs  as  the  gangue 
of  metallic  ores.  In  the  North  of  England,  it  is  the  gangue  of  the  lead  veins.  In  Derby- 
shire it  is  abundant,  and  also  in  Cornwall.  Common  in  the  mining  district  of  Saxony ;  fine 
near  Kougsberg  in  Norway.  In  the  dolomites  of  St.  Gothard  it  occurs  in  pink  octahedrons. 

Some  American  localities  are  :  Trumbull  and  Plymouth,  Conn.  ;  Muscolonge  Lake,  Jeffer- 
son Co.,  N.Y.,  in  gigantic  cubes  ;  Rossie,  St.  Lawrence  Co.  ;  near  the  Franklin  furnace,  N.  J.  ; 
Gallatin  Co. ,  111. ;  Thunder  Bay,  Lake  Superior ;  Missouri. 

SELLAITE  (Striiver). — Magnesium  fluoride,  MgF2.  Tetragonal.  Colorless.  Occurs  with 
anhydrite  at  Gerbulaz  in  Savoy. 

YTTROCJEHITE.— Composition  2(9CaF2  +  2YF2+CeF2)+3aq  (Ramm.).  Color  violet-blue, 
white.  Near  Fahlun,  Sweden  ;  Amity,  N.  Y.  ;  Paris,  Me.  ;  etc. 

FLUOCERITE.— Contains  (Berzelius)  €e03  82*64,  YO  1-12.     Sweden. 

FLUELLITE. — Contains  (Wollaston)  fluorine  and  aluminum.     Cornwall. 

CRYPTOHALITE. — Fluosilicate  of  ammonium.  Vesuvius.  Also  observed  at  Vesuvius, 
,  HF,  and  proidonite,  SiF4  (Scacchi). 


CRYOLITE. 


Triclinic  (DesCloizeatix  and  Websky).  Form  approaching  very  closely 
in  appearance  and  angles  to  the  cube  and  cubo- 
octahedron  of  the  isometric  system.  General  habit 
as  in  f.  460  ;  P(O)  A  T(I)  =  90°  2',  P(O]  A  M(l') 
'///,  =  90°  24',  M A  T(If\  7')  =  91°  57' ;  also  I  (!-$')  A  M 
(I1)  =  124°  30',  I  (W)  A  T (7)  =  124°  14'  (angles  by 
Websky).  Twins  common.  Cleavage  parallel  to 
the  three  planes  P,  J/",  T  ;  in  crystals  most  com- 
plete parallel  to  T,  in  masses  parallel  to  P.  Com- 
monly massive,  cleavable. 

H.  =  2-5.  G.  =  2-9-3-077.  Lustre  vitreous;  slightly 
pearly  on  O.  Color  snow-white  ;  sometimes  reddish 
or  brownish  to  brick-red  and  even  black.  Sub- 
transparent — translucent.  Immersion  in  water  in- 
creases the  transparency.  Brittle. 

Comp.— Na6AlF12  (or  6NaF+A-lF6)  =  Aluminum  13-0,  sodium  32-8,  fluorine  54-2=100. 

Fyr.,  etc. — Fusible  in  the  flame  of  a  candle.  B.B.  in  the  open  tube  heated  so  that  the 
flame  enters  the  tube*,  gives  off  hydrofluoric  acid,  etching  the  glass  ;  the  water  which  con- 
denses at  the  upper  end  of  the  tube  reacts  for  fluorine  with  Brazil-wood  paper.  In  the  for- 
ceps fuses  very  easily,  coloring  the  flame  yellow.  On  the  charcoal  fuses  easily  to  a  clear  bead, 
which  on  cooling  becomes  opaque ;  after  long  blowing,  the  assay  spreads  out,  the  sodium 
fluoride  is  absorbed  by  the  coal,  a  suffocating  odor  of  fluorine  is  given  off,  and  a  crust  of 
alumina  rem  ains,  which,  when  heated  with  cobalt  solution  in  O.  P. ,  gives  a  blue  color.  Soluble 
in  sulphuric  acid,  with  evolution  of  hydrofluoric  acid. 

Diff. — Distinguished  by  its  extreme  fusibility,  and  its  yielding  hydrofluoric  acid  in  the  open 
tube. 

Obs. — Occurs  in  a  bay  in  Arksut-fiord,  in  West  Greenland,  at  Evigtok,  where  it  constitutes 
a  large  bed  or  vein  in  gneiss.  It  is  used  for  making  soda,  and  soda  and  alumina  salts  ;  also 
in  Pennsylvania,  for  the  manufacture  of  a  white  glass  which  is  a  very  good  imitation  of 
porcelain. 

CHIOLITE.— GM=2-84-2-90.  Na3AlF9  (or  3NaF+AlF6).  CHODNEFFITE.— G.=3-01.  Na^l 
Fio  (or4NaF  +  A!F6)  Ramm.  The  two  minerals  are  alike  in  physical  characters,  occurring 
in  minute  tetragonal  pyramids  ;  both  from  Miask. 


FLUORINE   COMPOUNDS. 


243 


2.   HYDKOUS    FLUORIDES. 


PACHNOLITE.     Thomsenolifce. 

Monoclinic,  with  the  lateral   axes   equal    ("  clino-quadratic  "  Nordens- 
kiold).   c:b:d  =  1-044=  :  1  :  1  ;  C  =  92°  30'.   Prisms  slender, 
a  little  tapering  ;    /  horizontally  striated.     Cleavage  :  basal 
very  perfect.     Also  massive,  opal  or  chalcedony-like. 

Ii.=  2-5-4.  Gr.=  2-929-3-008,  of  crystals.  Lustre  vitreous, 
of  a  cleavage-face  a  little  pearly,  of  massive  waxy.  Color 
white,  or  with  a  reddish  tinge.  Transparent  to  translucent. 


460A 


Comp.— NaaCa2AlPls  +  2aq,  or  2NaF  +  2CaF2  +  A1F6  +  2aq  =  Fluorine 
51.28,  aluminum  12-28,  calcium  17*99,  sodium  10-35,  water  8 '10=100. 

Pyr.,  etc. — Fuses  more  easily  than  cryolite  to  a  clear  glass.  The  massive 
decrepitates  remarkably  in  the  flame  of  a  candle.  In  powder  easily  decom- 
posed by  sulphuric  acid. 

Obs. — Found  incrusting  the  cryolite  of  Greenland,  and  a  result  of  its 
alteration.     The  crystals  often  have  an  ochre-colored  coating,  especially  the 
terminal   portion;  they  are  sometimes  quite   large,   and   have  much  the 
appearance  of  cryolite.     The  mineral  was  first  described  by  Knop,  and  though  his  description 
of  the  crystals  does  nob  agree  with  that  given  above,  there  seems  to  be  no  doubt  that  the 
material  was  the  same,  which  has  since  been  investigated  by  Hagemann  (dimetric  pachnolite 
=  thomsenoUte),  Wohler  (pyroconite)  and  Koenig,  as  urged  by  the  latter. 

Knop  originally  described  two  varieties  of  the  mineral,  to  which  he  gave  the  name  pachno- 
lite. The  variety,  A,  appeared  in  large,  cuboid al  crystals,  with  cleavage  planes  parallel  to  the 
faces,  intersecting  at  angles  of  approximately  90°.  These  cleavage  planes  seemed  to  be  con- 
tinued on  into  the  mass  of  the  cryolite  on  which  the  crystals  were  implanted.  The  second 
variety,  B,  was  in  small  brilliant  crystals,  of  prismatic  form,  grouped  together  often  in  par- 
allel position  upon  the  cryolite  (hence  the  name,  from  vdxvrii  frost).  The  identity  of  the  two 
varieties  chemically  was  shown  by  the  analyses  of  Knop  and  Wohler.  The  crystals  of  variety 
B,  according  to  Knop,  had  /A  /=  81°  24',  etc. 

Knop  has  recently  (Jahrb.  Min.,  1876,  849)  suggested  the  possibility  that  the  crystals  of 
"  cryolite,"  upon  which  Websky  obtained  the  angles  quoted  on  the  preceding  page,  were  really 
identical  with  variety  A  of  pachnolite.  The  crystallographic  relation  of  the  two  species  is  not 
yet  clearly  made  out. 

ARKSUTITE,  HAGEMANNITE,  GEARKSUTITE,  all  from  Greenland ;  and  PROSOPITE,  from 
Altenberg. — Fluorine  minerals,  related  to  those  which  precede,  but  whose  exact  nature  is 
not  yet  known. 

RALSTONITE  (Brush}. — An  hydrous  aluminum  fluoride,  containing  also  a  little  magnesium 
and  sodium.  Occurs  in  minute  regular  octahedrons  on  the  cryolite  from  Greenland. 


244 


DESCEIPTIVE   MINERALOGY. 


V.  OXYGEN  COMPOUNDS. 


1.  OXIDES  OF  METALS  OF  THE  GOLD,  IKON,  OK  TIN  GKOTJPS. 

A.  ANHYDROUS  OXIDES.      (a)  PROTOXIDES,  RO(or  R>O). 

CUPRITE.     Bed  Copper  Ore.     Kothkupfererz,   Germ. 
Isometric   (see  figures  on  p.  IT).      Cleavage:    octahedral. 


461 


Sometimes 

cubes  lengthened  into  capillary  forms.     Also 
massive,  granular;  sometimes  earthy. 

H.=3-5-4.  G.=5-85-6-15.  Lustre  ada- 
mantine or  submetallic  to  earthy.  Color  red, 
of  various  shades,  particularly  cochineal-red  ; 
occasionally  crimson-red  by  transmitted  light. 
Streak  several  shades  of  brownish-red,  shin- 
ing. Subtransparent — subtranslucent.  Frac- 
ture conchoidal,  uneven.  Brittle. 


Comp.,  Var. — Cu2O=: Oxygen  11-2,  copper  88 '8 =100. 
Sometimes  affords  traces  of  selenium.  Chalcotriclrite 
is  a  variety  which  occurs  in  capillary  or  acicular  crys- 
tallizations, which  are  cubes  elongated  in  the  direction 
of  the  octahedral  axis.  It  also  occurs  earthy ;  Tile 
Ore  (Ziegelerz  Germ.}.  Brick-red  or  reddish-brown 
and  earthy,  often  mixed  with  red  oxide  of  iron  ;  some- 
times nearly  black. 

Pyr.,  etc. — Unaltered  in  the  closed  tube.  B.B.  in  the  forceps  fuses  and  colors  the  flame 
emerald-green;  if  previously  moistened  with  hydrochloric  acid,  the  color  imparted  to  the 
flame  is  momentarily  azure-blue  from  copper  chloride.  On  charcoal  first  blackens,  then  fuses, 
and  is  reduced  to  metallic  copper.  With  the  fluxes  gives  reactions  for  copper  oxide.  Soluble 
in  concentrated  hydrochloric  acid. 

Obs. — Occurs  in  Thuringia  ;  on  Elba,  in  cubes  ;  in  Cornwall ;  in  Devonshire  ;  in  isolated 
crystals,  in  lithomarge,  at  Chessy,  near  Lyons,  which  are  generally  coated  with  malachite, 
etc.  At  the  Somerville,  and  Flemington  copper  mines,  N.  J.  ;  at  Cornwall,  Lebanon  Co., 
Pa. ;  in  the  Lake  Superior  region. 

HYDROCUPRITE  (Oenth). — A  hydrous  cuprite.  Occurs  in  orange-yellow  coatings  on 
magnetite.  Cornwall,  Lebanon  Co.,  Pa. 

ZINCITE.     Red  Zinc  Ore.     Kothzinkerz,  Germ. 

Hexagonal.  O  A  1  =  118°-  T7 ;  c  —  1-6208.  In  qnartzoids  with  truncated 
summits,  and  prismatic  faces  L  Cleavage :  basal,  eminent ;  prismatic, 
sometimes  distinct.  Usual  in  foliated  grains  or  coarse  particles  and  masses ; 
also  granular. 

II.  =4-4-5.  Gr.  =  5-43-5-7.  Lustre  subadamantine.  Streak  orange-yel- 
low. Color  deep  red,  also  orange-yellow.  Translucent — subtranslucent. 
Fracture  subconchoidal.  Brittle. 

Comp. — ZnO= Oxygen  19*74,  zinc  80'26=100;  containing  manganese  as  an  unessential 
ingredient.  The  red  color  is  due  probably  to  the  presence  of  manganese  sesquioxide,  cer- 
tainly not  to  scales  of  hematite. 


OXYGEN   COMPOUNDS  — ANHYDROUS    OXIDES. 


245 


Pyr.,  etc. — Heated  in  the  closed  tube  blackens,  but  on  cooling  resumes  the  original  color. 
B.B.  infusible  ;  with  the  fluxes,  on  the  platinum  wire,  gives  reactions  for  manganese,  and  on 
charcoal  in  R.  F.  gives  a  coating  of  zinc  oxide,  yellow  while  hot,  and  white  on  cooling.  The 
coating,  moistened  with  cobalt  solution  and  treated  in  R.F.,  assumes  a  green  color.  Soluble 
in  acids  without  effervescence. 

Obs. — Occurs  with  franklinite  and  also  with  calcite  at  Stirling  Hill  and  Mine  Hill,  Sussex 
Co.,  N.  J. 

CALCOZINCITE. — Impure  zincite  (mixed  with  CaCO3,  etc.).     Stirling  Hill,  N.  J. 

TENORITE.    MELACONITE.     Schwarzkupfererz  (Kupferschwarze),  Germ. 

Orthorhombic  (tenorite),  crystals  from  Vesuvius.  Earthy ;  massive  ; 
pulverulent  (melaconite) ;  also  in  shining  flexible  scales  ;  also  rarely  in 
cubes  with  truncated  angles  (pseudomorphous  ?). 

H.=3.  G.— 6-25,  massive  (Whitney).  Lustre  metallic,  and  color  steel  or 
iron-gray  when  in  thin  scales  ;  dull  and  earthy,  with  a  black  or  grayish- 
black  color,  and  ordinarily  soiling  the  fingers  when  massive  or  pulverulent. 

Comp — CuO=Oxygen  20"15,  copper  79 '85=100 

Pyr.,  etc. — B.B.  in  O.F.  infusible;  other  reactions  as  for  cuprite  (p.  244).  Soluble  in 
hydrochloric  and  nitric  acids. 

Obs. — Found  on  lava  at  Vesuvius  in  minute  scales ;  and  also  pulverulent  (Scacchi,  who 
uses  the  name  melaconise  for  the  mineral).  Common  in  the  earthy  form  (melaconite)  about 
copper  mines,  as  a  result  of  the  decomposition  of  chalcopyrite  and  other  copper  ores.  Duck- 
town  mines  in  Tennessee,  and  Keweenaw  Point,  L.  Superior. 

PERICLASITE. — Essentially  magnesium  oxide,  MgO,  or  more  exactly  (Mg,Fe)0,  where 
Mg  :  Fe=20  :  1,  or  30  :  1.  Mt.  Somma. 

BUNSENITE.— NiO.  Found  at  Johanngeorgenstadt.  The  compound  MnO  has  been  found 
recently  in  Wermland,  in  masses  of  a  green  color,  and  with  cubic  cleavage.  (Blomstrand.) 

MASSICOT  (Bleiglatte). — PbO,  but  generally  impure.  Badenweiler,  Baden.  Mexico. 
Austin's  mines,  Va. 

HYDRARGYBITE. — HgO  ;  with  BORDOSITE,  AgCl  +  HgCl,  at  Los  Bordos,  Chili. 


SESQUIOXIDES.     GENERAL  FORMULA 


122C 


26';   (122C 
462 


25',  Kok- 
463 


CORUNDUM. 

Khombohedral.  E  A  E  =.86°  4',  O  A  1(72)  = 
scharof)  ;  c  =  1'363.  Cleavage :  basal,  some- 
times perfect,  but  interrupted,  commonly  im- 
perfect in  the  blue  variety;  rhombohedral,  of  ten 
perfect.  Large  crystals  usually  rough.  Twins  : 
composition-face  E.  Also  massive  granular  or 
impalpable  ;  often  in  layers  from  composition 
parallel  to  R. 

LI.  — 9.  G.= 3-909-4-16.  Lustre  vitreous; 
sometimes  pearly  on  the  basal  planes,  and  occa- 
sionally exhibiting  a  bright  opalescent  star  of 
six  rays  in  the  direction  of  the  axis.  Color  blue, 
red,  yellow,  brown,  gray,  and  nearly  white ; 
streak  uncolored.  Transparent — translucent. 
Fracture  conchoidal  —  uneven.  Exceedingly 
tough  when  compact. 

Comp.,  Var — Pure  alumina  A103=0xygen  46'8,  aluminum  53'2=100.     There  are  three 


246 


DESCKIPTIVE   MINERALOGY. 


subdivisions  of  the  species  prominently  recognized  in  the  arts,  and  until  early  in  this  century 
regarded  as  distinct  species  ;  but  which  actually  differ  only  in  purity  and  state  of  crystalliza- 
tion or  structure. 

VAR.  1.  SAPPHIRE — Includes  the  purer  kinds  of  fine  colors,  transparent  to  translucent, 
useful  as  gems.  Stones  are  named  according  to  their  colors  ;  true  JSffdff,  or  Oriental  Ruby, 
red  ;  0.  Topas,  yellow  ;  0.  Emerald,  green  ;  0.  Amethyst,  purple. 

2.  CORUNDUM. — Includes  the  kinds  of  dark  or  dull  colors  and  not  transparent,  colors  light 
blue  to  gray,  brown,  and  black.     The  original  adamantine  spar  from  India  has  a  dark  gray- 
ish smoky-brown  tint,  but  greenish  or  bluish  by  transmitted  light,  when  translucent,  and 
either  in  distinct  crystals  often  large,  or  cleavable-massive.     It  is  ground  and  used  as  a  polish- 
ing material,  and  being  purer,  is  superior  in  this  respect  to  emery.     It  was  thus  employed  in 
ancient  times,  both  in  India  and  Europe. 

3.  EMERY,   Schmirgel,    Germ. — Includes  granular  corundum,   of  black  or  grayish- black 
color,  and  contains  magnetite  or  hematite  intimately  mixed.     Feels  and  looks  much  like  a 
black  fine-grained  iron  ore,  which  it  was  long  considered  to  be.     There  are  gradations  from  the 
evenly  fine-grained  emery  to  kinds  in  which  the  corundum  is  in  distinct  crystals.     This  last 
is  the  case  with  part  of  that  at  Chester,  Massachusetts. 

Pyr.,  etc. — B.B.  unaltered  ;  slowly  dissolved  in  borax  and  salt  of  phosphorus  to  a  clear 
glass,  which  is  colorless  when  free  from  iron  ;  not  acted  upon  by  soda.  The  finely  pulverized 
mineral,  after  heating  with  cobalt  solution,  gives  a  beautiful  blue  color.  Not  acted 
upon  by  acids,  but  converted  into  a  soluble  compound  by  fusion  with  potassium  bisulphate 
or  soda.  Friction  excites  electricity,  and  in  polished  specimens  the  electrical  attraction  con- 
tinues for  a  considerable  length  of  time. 

Diff- —  Distinguished  by  its  hardness,  scratching  quartz  and  topaz  ;  its  infusibility  and  its 
high  specific  gravity. 

Obs. — This  species  is  associated  with  crystalline  rocks,  as  granular  limestone  or  dolomite, 
gneiss,  granite,  mica  slate,  chlorite  slate.  The  fine  sapphires  are  usually  obtained  from  the 
beds  of  rivers,  either  in  modified  hexagonal  prisms  or  in  rolled  masses,  accompanied  by  grains 
of  magnetic  iron  ore,  and  several  species  of  gems.  The  emery  of  Asia  Minor,  according  to 
Dr.  Smith,  occurs  in  granular  limestone. 

Sapphires  occur  in  Ceylon ;  the  East  Indies  ;  China,  Corundum,  at  St.  Gothard  ;  in  Pied- 
mont ;  Urals ;  Bohemia.  Emery  is  found  in  large  boulders  on  some  of  the  Grecian  islands  ; 
also  in  Asia  Minor,  near  Ephesus,  etc.  In  N.  America,  in  Massachusetts,  at  Chester,  corun- 
dum and  emery  in  a  large  vein ;  also  in  Westchester  Co.,  N.  Y.  In  New  York,  at  Warwick 
and  Amity.  In  Pennsylvania,  in  Delaware  Co. ,  and  Chester  Co.  In  western  N.  Carolina, 
at  many  localities  in  large  quantities,  and  sometimes  in  crystals  of  immense  size.  In  Georgia, 
in  Cherokee  Co.  In  California,  in  Los  Angeles  Co.  ;  in  the  gravel  on  the  Upper  Missouri 
.River  in  Montana. 


HEMATITE.    Specular  Iron.     Eisenglanz,  Kotheisenerz,  Germ. 
Khombohedral.      R  A  R  =  86°    10',     0  A  R  =  122°    30'  :    c  =  1  '3591. 


O  A  f  2  =  118°  53',  O  A  I3  =  103°  32,  'jR  A  f  2  =  154°  2'.     Cleavage  :  par- 
allel to  R  and  O;  often  indistinct.     Twins:  twinning-plane  R ;  also  O 


465 


466 


Vesuvius. 


Elba. 


Elba. 


(f .  267,  p.  91).  Also  columnar — granular,  botryoidal,  and  stalactitic  shapes  ; 
also  lamellar,  laminae  joined  parallel  to  <?,  and  variously  bent,  thick  or 
thin ;  also  granular,  friable  or  compact. 


OXYGEN   COMPOUNDS ANHYDKOUS   OXIDES.  247 

H.=:5'5-6'5.  G.=4'5-5'3;  of  some  compact  varieties,  as  low  as  4-2. 
Lustre  metallic  and  occasionally  splendent ;  sometimes  earthy.  Color  dark 
steel-gray  or  iron-black ;  in  -very  thin  particles  blood-red  by  transmitted 
light ;  when  earthy,  red.  Streak  cherry-red  or  reddish-brown.  Opaque, 
except  when  in  very  thin  laminae,  which  are  faintly  translucent  and  blood- 
red.  -Fracture  subconchoidal,  uneven.  Sometimes  attractable  by  the 
magnet,  and  occasionally  even  magnetipolar. 

Comp.,  Var. — Iron  sesquioxide,  Fe03=0xygen  30,  iron  70=100.  Sometimes  containing 
titanium  and  magnesium. 

The  varieties  depend  on  texture  or  state  of  aggregation,  and  in  some  cases  the  presence  of 
impurities. 

Var.  1.  Specular.  Lustre  metallic,  and  crystals  often  splendent,  whence  the  name  specular 
iron,  (b)  When  the  structure  is  foliated  or  micaceous,  the  ore  is  called  micaceous  hematite 
(Eisenglimmer).  2.  Compact  columnar  ;  or  fibrous.  The  masses  of  ten  long  radiating  ;  lustre 
submetallic  to  metallic  ;  color  brownish-red  to  iron-black.  Sometimes  called  t\d  hematite, 
the  name  hematite  among  the  older  mineralogists  including  the  fibrous,  stalactitic,  and  other 
solid  massive  varieties  of  this  species,  limoiiite,  and  turgite.  8.  lied  Ochreous.  Red  and 
earthy.  Often  specimens  of  the  preceding  are  red  ochreous  on  some  parts.  Reddle  and  red 
chalk  are  red  ochre,  mixed  with  more  or  less  clay.  4.  Clay  Iron-stone  ;  Argillaceous  hematite. 
Hard,  brownish-black  to  reddish-brown,  heavy  stone  ;  often  in  part  deep-red  ;  of  submetallic 
to  unmetallic  lustre  ;  and  affording,  like  all  the  preceding,  a  red  streak.  It  consists  of  iron 
sesquioxide  with  clay  or  sand,  and  sometimes  other  impurities. 

Pyr.,  etc. — B.B.  infusible;  on  charcoal  in  R.F.  becomes  magnetic;  with  borax  in  O.F. 
gives  a  bead,  which  is  yellow  while  hot  and  colorless  on  cooling  ;  if  saturated,  the  bead 
appears  red  while  hot  and  yellow  on  cooling  ;  in  R.F.  gives  a  bottle-green  color,  and  if  treated 
on  charcoal  with  metallic  tin,  assumes  a  vitriol-green  color.  With  soda  on  charcoal  in  R.F. 
is  reduced  to  a  gray  magnetic  metallic  powder.  Soluble  in  concentrated  hydrochloric  acid. 

DifF. — Distinguished  from  magnetite  by  its  red  streak,  also  from  limonite  by  the  same 
means,  as  well  as  by  its  not  containing  water  ;  from  turgite  by  its  greater  hardness  and  by 
its  not  decrepitating  B.B.  It  is  hard ;  and  infusible. 

Obs. — This  ore  occurs  in  rocks  of  all  ages.  The  specular  variety  is  mostly  confined  to  crys- 
talline or  metamorphic  rocks,  but  is  also  a  result  of  igneous  action  about  some  volcanoes,  as 
at  Vesuvius.  Traversella  in  Piedmont ;  the  island  of  Elba,  afford  fine  specimens  ;  also  St. 
Gothard,  often  in  the  form  of  rosettes  (Eisenrose],  and  Cavradi  in  Tavetsch ;  and  near  Limoges, 
France.  At  Etna  and  Vesuvius  it  is  the  result  of  volcanic  action.  Arendal  in  Norway,  Long- 
Ian  in  Sweden,  Framont  in  Lorraine,  Dauphiny,  also  Cleator  Moor  in  Cumberland,  are  other 
localities. 

In  N.  America,  widely  distributed,  and  sometimes  in  beds  of  vast  thickness  in  rocks  of  the 
Archaean  age,  as  in  the  Marquette  region  in  northern  Michigan ;  and  in  Missouri,  at  the  Pilot 
Knob  and  the  Iron  Mtn. ;  in  Arizona  and  New  Mexico.  Some  of  the  localities,  interesting 
for  their  specimens,  are  in  northern  New  York,  etc. ;  Woodstock  and  Aroostook,  Me. ;  at 
Hawley,  Mass.  ;  at  Piermont,  N.  H. 

This  ore  affords  a  considerable  portion  of  the  iron  manufactured  in  different  countries.  The 
varieties,  especially  the  specular,  require  a  greater  degree  of  heat  to  melt  than  other  ores, 
but  the  iron  obtained  is  of  good  quality.  Pulverized  red  hematite  is  employed  in  polishing 
metals,  and  also  as  a  coloring  material.  The  fine-grained  massive  variety  from  England 
(bloodstone),  showing  often  beautiful  conchoidal  fracture,  is  much  used  for  burnishing  metals. 
Red  ochre  is  valuable  in  making  paint. 

MARTITE  is  iron  sesquioxide  under  an  isometric  form,  occurring  in  octahedrons  or  dodeca- 
hedrons like  magnetite,  and  supposed  to  be  pseudomorphous,  mostly  after  magnetite.  H.  = 
6-7.  G.  =4 -809-4 -832,  Brazil,  Breith.  ;  5  "33,  Monroe,  N.  Y.,  Hunt.  Lustre  submetallic. 
Color  iron-black,  sometimes  with  a  bronzed  tarnish.  Streak  reddish-brown  or  purplish-brown. 
Fracture  couchoidal.  Not  magnetic,  or  only  feebly  so.  The  crystals  are  sometimes  imbed- 
ded in  the  massive  sesquioxide.  They  are  distinguished  from  magnetite  by  their  red  streak, 
and  very  feeble,  if  any,  action  on  the  magnetic  needle. 

Found  in  Vermont  at  Chittenden;  in  the  Marquette  iron  region  south  of  L.  Superior; 
Bass  lake,  Canada  West ;  Digby  Neck,  Nova  Scotia ;  at  Monroe,  N.  Y.  ;  in  Moravia,  near 
Schonberg,  in  granite. 

MENACCANITE.    ILMENITE.     Titanic  Iron  Ore.     Titaneisen,  Germ. 
Rhombohedral ;  tetartohedral  to  the  hexagonal  type.     R  A  R  =  85°  30' 


248  DESCRIPTIVE   MINERALOGY. 

56"  (Koksch.),  c  =  1'38458.     Angles  nearly   as    in   hematite.      Often    a 

cleavage  parallel  with  the  terminal  plane,  but 
probably  due  to  planes  of  composition.  Crystals 
usually  tabular.  Twins :  twinn ing-plane  O ; 
sometimes  producing,  when  repeated,  a  form 
resembling  f.  468.  Often  in  thin  plates  or 
laminae  ;  massive  ;  in  loose  grains  as  sand. 

H.=5-6.  G.=4'5-5.  Lustre  submetallic. 
Color  iron-black.  Streak  submetallic,  powder 
black  to  brownish-red.  Opaque.  Fracture  con- 

choidal.   Influences  slightly  the  magnetic  needle. 

Comp.,  Var. — (Ti,Fe)2O3  (or  hematite,  with  part  of  the  iron  replaced  by  titanium),  the  pro- 
portion of  Ti  to  Fe  varying.  Mosander  assumes  the  proportion  of  FeO  :  TiO2  to  be  always 
1:1,  and  that  in  addition  variable  amounts  of  Fe03  are  present  in  the  different  varieties. 
The  extensive  investigations  of  Rammelsberg  have  led  him  to  write  the  formula  like  Mosan- 
der (FeO,Ti02)+nFeO3  (notice  here  that  FeO,TiO2=R03).  This  method  has  the  advantage 
of  explaining  the  presence  of  the  magnesium,  occurring  sometimes  in  considerable  amount,  it 
replacing  the  iron  (FeO).  The  first  formula  given  requires  the  assumption  of  Mga03.  Friedel 
and  Guerin  have  recently  discussed  the  same  subject  (Ann.  Ch.  Phys. ,  V.,  viii.,  38,  1876). 

Sometimes  contains  manganese.  The  varieties  recognized  arise  mainly  from  the  proportions 
of  iron  to  titanium.  No  satisfactory  external  distinctions  have  yet  been  made  out. 

The  following  analyses  will  illustrate  the  wide  r&nge  in  composition  : 

TiO2  Fe03  FeO  MnO  MgO 

1.  IlmenMts.,  l&nenite  46 -92  iO'74  37'86  2'73  1-14=99 "39,  Mosander. 

2.  Snarum                       10'02  77'17  8-52      1'33,  A1O3  1 '46=98-50,  Ramm. 

3.  Warwick,  N.  Y.         57'71 26'82  (K)0  13-71=9914,  Ramm. 

Pyr.,  etc. — B.B.  infusible  in  O.F.  although  Rlightly  rounded  on  the  edges  in  R.  F.  With 
borax  and  salt  of  phosphorus  reacts  for  iron  in  O.F. ,  and  with  the  latter  flux  assumes  a  more 
or  less  intense  brownish-red  color  in  R.F.  ;  this  treated  with  tin  on  charcoal  changes  to  a 
violet-red  color  when  the  amount  of  titanium  is  not  too  small.  The  pulverized  mineral, 
heated  with  hydrochloric  acid,  is  slowly  dissolved  to  a  yellow  solution,  which,  filtered  from 
the  undecomposed  mineral  and  boiled  with  the  addition  of  tin-foil,  assumes  a  beautiful  blue 
or  violet  color.  Decomposed  by  fusion  with  sodium  or  potassium  bisulphate. 

Diff. — Resembles  hematite,  but  has  a  submetallic,  nearly  black,  streak. 

Obs. — Some  of  the  principal  European  localities  of  this  species  are  :  Krageroe,  Egersund, 
Arendal,  Norway;  Uddewalla,  Sweden;  Ilmen  Mts.  (ilmenite) ;  Iserwiese,  Riesengebirge  (ise?- 
ine) ;  Aschaffenburg ;  Eisenach ;  St.  Cristophe  (cnchtonite). 

Occurs  in  Warwick,  Amity,  and  Monroe,  Orange  Co.,  N.  Y. ;  also  near  Edenville  ;  at  Ches- 
ter and  South  Royalston,  Mass.  ;  at  Bay  St.  Paul  in  Canada;  also  with labradorite  at  Chateau 
Richer.  Grains  are  found  in  the  gold  sands  of  California. 


PEROFSKITE. 

Isometric,  Rose  (fr.  Ural).  Habit  cubic,  with  secondary  planes  incom- 
pletely developed ;  in  cubes,  octahedrons,  and  cubo-octahedrons,  from 
Arkansas.  Twins :  twinning-plane  octahedral,  Magnet  Cove,  Ark. ;  also 
like  f.  276,  p.  93,  Achinatovsk.  Cleavage :  parallel  to  the  cubic  faces 
rather  perfect. 

H.=5'5.  G.= 4*02-4  *04.  Lustre  metallic — adamantine.  Color  pale 
yellow,  honey-yellow,  orange-yellow,  reddish-brown,  grayish-black  to  iron- 
black.  Streak  colorless,  grayish.  Transparent  to  opaque.  Double  refract- 
ing. 


OXYGEN   COMPOUNDS. ANHYDROUS    OXIDES.  249 

Comp.— (Ca+Ti)03=R-03=:Titanic  oxide  59'4,  lime  40'6=100. 

Pyr.,  etc. — In  the  forceps  and  on  charcoal  infusible.  With  salt  of  phosphorus  in  O.F.  dis- 
solves easily,  giving  a  bead  greenish  while  hot,  which  becomes  colorless  on  cooling;  in  R.F. 
the  bead  changes  to  grayish-green,  and  on  cooling  assumes  a  violet-blue  color.  Entirely  de- 
composed by  boiling  sulphuric  acid. 

Obs. — Occurs  at  Achmatovsk  in  the  Ural ;  at  Scheelingen  in  the  Kaisersthul ;  in  the  valley 
of  Zermatt ;  at  Wildkreuzjoch  in  the  Tyrol.  Also  at  Magnet  Cove,  Arkansas. 

DesCloizeaux  has  found  that  the  yellow  crystals  from  Zermatt  have  a  complex  twinned 
structure,  and  are  optically  biaxial.  Kokscharof,  in  his  latest  investigations,  has  shown  that 
the  Kussian  specimens  also  exhibit  phenomena  in  polarized  light  analogous  to  those  of  biaxial 
crystals,  though  irregular.  He  proves,  however,  that  crystallographically  the  crystals  ex- 
amined by  him  were  unquestionably  isometric,  and  adds  also  that  almost  all  the  Russian 
perofskite  crystals  are  penetration -twins.  The  latter  fact  explains  the  commonly  observed 
striations  on  the  cubic  planes,  as  also  the  incompleteness  in  the  development  of  the  other 
forms.  He  refers  the  optical  irregularities  to  the  want  of  homogeneity  in  the  crystals.  Des- 
Cloizeaux speaks  of  inclosed  lamellse  of  a  doubly-refracting  substance  analogous  to  the  para- 
site in  boracite  crystals  (p.  154). 

HYDROTITANITE. — A  decomposition-product  of  perofskite  crystals  from  Magnet  Cove, 
Arkansas.  Form  retained  but  color  changed  to  yellowish -gray  (Koanig). 


(c)  COMPOUNDS  OF  PROTOXIDES  AND  SESQUIOXIDES,*  RRO4(or  RO+RO3). 
Spinel  Group.     Isometric  (Octahedral). 

SPINEL. 

Isometric.     Habit  octahedral.     Faces  of  octahedron  sometimes  convex. 
Cleavage:  octahedral.     Twins:  twinning-plane  1. 

II.  =  8.  G.  =  3'5-4'l.  Lustre  vitreous  ;  splendent — 
nearly  dull.  Color  red  of  various  shades,  passing  into 
blue,  green,  yellow,  brown,  and  black;  occasionally 
almost  white.  Streak  white.  Transparent — nearly 
opaque.  Fracture  conchoidal. 


Oomp.,  Var. — The  spin  els  proper  have  the  formula  MgM04(=MgO 
+ A103),  or  in  other  words  contain  chiefly  magnesium  and  aluminum, 
with  the  former  replaced  in  part  by  iron  (Fe),  calcium  (Ca),  and  man- 
ganese (Mn) ;  and  the  latter  by  iron  (Fe).  There  is  hence  a  grada- 
tion into  kinds  containing  little  or  no  magnesium,  which  stand  as 
distinct  species,  viz.,  Hercynite  and  GaJmite.  MgA104= Alumina 
72.  magnesia  28=100. 

Var.  1 .  Ruby,  or  Magnesia  Spinel.  — Clear  red  or  reddish ;  transparent  to  translucent ; 
sometimes  subtranslucent.  G-.  =3 '52-3 '58.  Composition  MgA104,  with  little  or  no  Fe,  and 
sometimes  chromium  as  a  source  of  the  red  color.  2.  Ceylonite,  or  Ivon-Magnesia  Spinel. 
Color  dark-green,  brown  to  black,  mostly  opaque  or  nearly  so.  G.— 3 '5-3 '6.  Composition 
MgM04  +  FeA:lO4.  Sometimes  the  Al  is  replaced  in  part  by  Fe.  3.  Picotite.  Contains  over 
7  p.  c.  of  chromium  oxide.  Color  black.  Lustre  brilliant.  G.  =4'08.  The  original  was 
from  a  rock  occurring  about  L.  Lherz,  called  Lherzolite. 

Pyr.,  etc — B.B.  alone  infusible;  the  red  variety  turns  brown,  and  even  black  and 
opaque,  as  the  temperature  increases,  and  on  cooling  becomes  first  green,  and  then  nearly 
colorless,  and  at  last  resumes  the  red  color.  Slowly  soluble  in  borax,  more  readily  in  salt  of 
phosphorus,  with  which  it  gives  a  reddish  bead  while  hot,  becoming  faint  chrome-green  on 

*  The  compounds  here  considered  are  sometimes  regarded  as  salts  of  the  acids,  HaROu, 
that  is,  as  alummates,  ferriles,  etc. 


250 


DESCRIPTIVE   MINERALOGY. 


cooling.  The  black  varieties  give  reactions  for  iron  with  the  fluxes.  Soluble  with  difficulty 
in  concentrated  sulphuric  acid.  Decomposed  by  fusion  with  sodium  or  potassium  bisulphate. 

Diff.  —  Distinguished  by  its  octahedral  form,  hardness,  and  infusibility  ;  magnetite  is 
attracted  by  the  magnet,  and  zircon  has  a  higher  specific  gravity. 

Obs.  —  Spinel  occurs  imbedded  in  granular  limestone,  and  with  calcite  in  serpentine,  gneiss, 
and  allied  rocks.  It  also  occupies  the  cavities  of  masses  ejected  from  some  volcanoes,  e.g., 
Mt.  Somma. 

Fine  spinels  are  found  in  Ceylon  ;  in  Siam,  as  rolled  pebbles  in  the  channels  of  rivers. 
Occur  at  Aker  in  Sweden  ;  also  at  Monzoni  in  the  Fassathal. 

From  Amity,  N.  Y.,  to  Andover,  N.  J.,  a  distance  of  about  30  miles,  is  a  region  of  granular 
limestone  and  serpentine,  in  which  localities  of  spinel  abound  ;  numerous  about  Warwick, 
and  at  Monroe  and  Cornwall.  Franklin,  Sterling,  Sparta,  Hamburgh,  and  Vernon,  IS".  J.  , 
are  other  localities.  At  Antwerp,  Jefferson  Co.,  N.  Y.  ;  at  Bolton  and  elsewhere  in  Mass. 

HERCYNITE.  —  FeAlO4  (or  FeO  +  A103).     Color  black.     Massive.     Bohemia. 

JACOBSITE  (Damour).  —  KRO4,  or  (Mn,Mg)  (Fe,Mn)O4.  Color  deep  black.  Occurs  in  dis- 
torted octahedrons  (magnetic)  in  a  crystalline  limestone  at  Jacobsberg,  Sweden. 


GAHNITE.     Zinc  Spinel. 

Isometric.     In  octahedrons,  dodecahedrons,  etc.,  like  spinel. 

H.  =7*5-8.  G.=4-4'6.  Lustre  vitreous,  or  sornevvrhat  greasy.  Color 
dark  green,  grayish-green,  deep  leek-green,  greenish-black,  bluish-black, 
yellowish-  or  grayish-brown  ;  streak  grayish.  Subtranslucent  to  opaque. 

Comp.,  Var.  —  ZnA104=  Alumina  61  -3,  oxide  of  zinc  38'7=100  ;  with  little  or  no  magnesium. 
The  zinc  sometimes  replaced  in  small  part  by  manganese  or  iron  (Mn,Fe),  and  the  aluminum 
in  part  by  iron  (Fe). 

Var.  1.  Automolite,  or  Zinc  Gahnite  ;  with  sometimes  a  little  iron.  G.  =4*1-4'G.  Colors  as 
above  given.  2.  Dysluite,  or  Zinc-Manganese-  Iron  Gahnite.  Composition  (Zn,Fe,Mn) 
(rtl,Fe)O4.  Color  yellowish-brown  or  grayish-brown.  G.  =4-4  "6.  Form  the  octahedron,  or 
the  same  with  truncated  edges.  3.  Kreittonite,  or  Zinc-  Iron  Gahnite.  Composition  (Zn, 
Fe,Mg)(M,FeyO4.  Occurs  in  crystals,  and  granular  massive.  H.=7-8.  G.  =4'48-4'89. 
Color  velvet  to  greenish-  black  ;  powder  grayish-  green.  Opaque. 

Pyr.,  etc.  —  Gives  a  coating  of  zinc  oxide  when  treated  with  a  mixture  of  borax  and  soda 
on  charcoal.  Otherwise  like  spinel. 

Obs.  —  Automolite  is  found  at  Fahlun,  Sweden  ;  Franklin,  N.  Jersey  ;  Canton  mine,  Ga.  ; 
Dysluite  at  Sterling,  N.  J.  ;  Kreittonite  at  Bodenmais  in  Bavaria. 


MAGNETITE.     Magnetic  Iron  Ore.     Magneteisenstein,  Magneteisenerz,  Germ. 

Isometric.     The  octahedron  and  dodecahedron  the  most  common  forms. 

472  474  475 


Achmatovsk.  Haddam. 

Tig.  475  is  a  distorted  dodecahedron.    Cleavage :  octahedral,  perfect  to 


OXYGEN   COMPOUNDS. ANHYDROUS   OXIDES.  251 

imperfect.  Dodecahedral  faces  commonly  striated  parallel  to  the  longer 
diagonal.  Twins :  t  winning-plane,  1 ;  also  in  dendrites,  branching  at  angles 
of  60°  (f.  277,  p.  93).  Massive,  structure  granular — particles  of  various 
sizes,  sometimes  impalpable. 

I-I.=5'5-6'5.  G. =4-9-5-2.  Lustre  metallic — snbmetallic.  Color  iron- 
black  ;  streak  black.  Opaque ;  but  in  mica  sometimes  transparent  or 
nearly  so  ;  and  varying  from  almost  colorless  to  pale  smoky-brown  and 
black.  Fracture  subconchoidal,  shining.  Brittle.  Strongly  magnetic, 
sometimes  possessing  polarity. 

Comp.,  Var.— FeFe04  (or  Fe3O4)=FeO+FeO3=Oxygen  27'6,  iron  72 "4= 100  ;  or  iron  ses- 
quioxide  68*97,  iron  protoxide  31 '03=  100.  The  iron  sometimes  replaced  in  small  part  by 
magnesium.  Also  sometimes  titaniferous. 

From  the  normal  proportion  of  Fe  to  Fe,  1:1,  there  is  occasionally  a  wide  variation,  and 
thus  a  gradual  passage  to  the  sesquioxide  Fe03 ;  and  this  fact  may  be  regarded  as  evidence 
that  the  octahedral  Fe03,  martite,  is  only  an  altered  magnetite. 

Pyr.,  etc. — B.B.  very  difficultly  fusible.  In  O.F.  loses  its  influence  on  the  magnet.  With 
the  fluxes  reacts  like  hematite.  Soluble  in  hydrochloric  acid. 

DifF. — Distinguished  from  other  members  of  the  spinel  group,  as  also  from  garnet,  by  its 
being  attracted  by  the  magnet,  as  well  as  by  its  high  specific  gravity.  Also,  when  massive, 
by  its  black  streak  from  hematite  and  limonite. 

Obs. — Magnetite  is  mostly  confined  to  crystalline  rocks,  and  is  most  abundant  in  metainor- 
phic  rocks,  though  found  also  in  grains  in  eruptive  rocks.  In  the  Archa3an  rocks  the  beds  are 
of  immense  extent,  and  occur  under  the  same  conditions  as"  those  of  hematite.  It  is  an  ingre- 
dient in  most  of  the  massive  variety  of  corundum  called  emery.  The  earthy  magnetite  is 
found  in  bogs  like  bog-iron  ore. 

Extensive  deposits  occur  at  Arendal,  Norway  ;  Dannemora  and  the  Tiiberg  in  Smaoland ; 
in  Lapland.  Fahlun  in  Sweden,  and  Corsica,  afford  octahedral  crystals. 

In  N.  America,  it  constitutes  vast  beds  in  the  Archaean,  in  the  Adirondack  region,  in 
Northern  N.  York  ;  also  in  Canada ;  at  Cornwall  in  Pennsylvania,  and  at  Magnet  Cove, 
Arkansas.  Also  found  in  Putnam  Co.  (Tilly  Foster  Mine),  N.  Y.,  etc.  In  Conn.,  at  Haddam. 
Tn  Penn.,  at  Chester  Co.  ;  in  mica  at  Pennsbury.  In  California,  in  Sierra  Co.  ;  in  Plumas 
Co.,  and  elsewhere.  In  a.  Scotia,  Digby  Co.,  Nichol's  Mt. 

MAGNESIOFEBKITE  (magnoferrite). — MgFeO4.  In  octahedrons ;  resembling  magnetite. 
Vesuvius. 

FRANK  UNITE. 

Isometric.  Habit  octahedral.  Cleavage :  octahedral,  indistinct.  Also 
massive,  coarse  or  fine  granular  to  compact. 

H.— 5-5-6-5.  G-.=5-069.  Lustre  metallic.  Color  iron-black.  Streak 
dark  reddish-brown.  Opaque.  Fracture  conchoidal.  Brittle.  Acts  slightly 
on  the  magnet. 

Comp. — (Fe,Zn,Mn)  (Fe,Mn)O4,  or  corresponding  to  the  general  formula  of  the  spinel 
group,  though  varying  much  in  relative  amounts  of  iron,  zinc,  and  manganese.  Analysis, 
Sterling  Hill,  N.  J.,  f  FeO3  67-43,  A103  0'65,  FeO  15 -65,  ZnO  6-78,  MnO  9'53=100'12,  Seyms. 
Q.  ratio  for  B  :  ft=l  :  1  nearly.  In  a  crystal  from  Mine  Hill,  N.  J.,  Seyms  found  4'44  p.  c. 
Mn03. 

The  evolution  of  chlorine  in  the  treatment  of  the  mineral  is  attributed  by  v.  Kobell  to  the 
presence  of  a  little  Mn03  (0.80  p.  c.)  as  mixture,  which  Rammelsberg  observes  may  have 
come  from  the  oxidation  of  some  of  the  protoxide  of  manganese. 

Pyr.,  etc. — B.B.  infusible.  With  borax  in  O.F.  gives  a  reddish  amethystine  bead  (man- 
ganese), and  in  R.F.  this  becomes  bottle-green  (iron).  With  soda  gives  a  bluish -green  man- 
ganate,  and  on  charcoal  a  faint  coating  of  zinc  oxide,  which  is  much  more  marked  when  a 
mixture  of  borax  and  soda  is  used.  Soluble  in  hydrochloric  acid,  with  evolution  of  a  small 
amount  of  chlorine. 

Diff.— Resembles  magnetite,  bub  is  only  slightly  attracted  by  the  magnet ;  it  also  reacts 
for  zinc  on  charcoal  B.B. 


£52 


DESCRIPTIVE   MINERALOGY. 


Obs. — Occurs  in  cubic  crystals  near  Eibach  in  Nassau ;  in  amorphous  masses  at  Altenberg, 
near  Aix  la  Chapelle.  Abundant  at  Hamburg,  N.  J.,  near  the  Franklin  furnace;  also  at 
Stirling  Hill,  in  the  same  region. 

CHROMITE.     Chromic  Iron.     Chromeisenstein,  Germ. 

Isometric.  In  octahedrons.  Commonly  massive ;  structure  fine  granu- 
lar or  compact. 

H.=5-5.  Gr.— 4-321-4-568.  Lustre  snbinetallic.  Streak  brown.  Color 
between  iron-black  and  brownish-black.  Opaque.  Fracture  uneven. 
Brittle.  Sometimes  magnetic. 

Comp Fe^r04,  or  (Fe,Mg,Cr)  (Al,Fe,Or)04.  Fe6r04=Iron  protoxide  32,  chromium  ses- 

quioxide  68—100.  Magnesia  is  generally  present,  and  in  amounts  varying  from  6-24  p.  c. 

Pyr.,  etc. — B.B.  in  O.F.  infusible;  in  R.F.  slightly  rounded  on  the  edges,  and  becomes 
magnetic.  With  borax  and  salt  of  phosphorus  gives  beads,  which,  while  hot,  show  only  a 
reaction  for  iron,  but  on  cooling  become  chrome-green ;  the  green  color  is  heightened  by 
fusion  on  charcoal  with  metallic  tin.  Not  acted  upon  by  acids,  but  decomposed  by  fusion 
with  potassium  or  sodium,  bisulphate. 

Diff. — Distinguished  from  magnetite  by  the  reaction  for  chromic  acid  with  the  blowpipe. 

Obs. — Occurs  in  serpentine,  forming  veins,  or  in  imbedded  masses.  It  assists  in  giving  the 
variegated  color  to  verde-antique  marble.  Also  occurs  in  meteorites. 

Occurs  in  Syria  ;  Shetland  ;  in  Norway ;  in  the  Department  du  Var  in  France  ;  in  Silesia 
and  Bohemia  ;  in  the  Urals;  in  New  Caledonia.  At  Baltimore,  Md.,  in  the  Bare  Hills  ;  at 
Cooptown.  In  Pennsylvania,  in  Chester  Co.  ;  at  Wood's  Mine,  near  Texas,  Lancaster  Co. , 
etc.  Chester,  Mass.  In  California,  in  Monterey  Co. ,  etc. 

This  ore  affords  the  chromium  oxide,  used  in  painting,  etc.  The  ore  employed  in  England 
is  obtained  mostly  from  Baltimore,  Drontheim  in  Norway,  and  the  Shetland  Isles. 

CHROMPICOTITB  (Petersen). — A  maguesian  chromite.     Color  black.     New  Zealand. 


URANINITE   (Pitchblende;  Uranpecherz,    Germ.}.— U3O&(UO2-t-2U03). 
Saxony,  etc. 


Massive.     Black. 


CHRYSOBERYL. 

Orthorhombic.     /A  I—  129°  38',  0  A  14  =  129°  1' ;  c  :  I  :  a  =  1-2285  : 

2-1267  : 1.     i-l  A 1  =  136°  52',  i-l  A 

476  477  2-2  =  12_8°  52',  i4  A  1-2  =  120°  T. 

Plane  i-l  vertically  striated  ;  and 
sometimes  also  i-$,  and  other  verti- 
cal planes.  Cleavage :  \-l  quite 
distinct ;  i-l  imperfect ;  i-l  more 
so.  Twins :  twinning-plane  3-£,  as 
in  f.  477  (see  p.  97),  made  up  of  6 
parts  by  the  crossing  of  3  crystals. 
'H.  =  8-5.  G.  =  3-5-3-84.  Lustre 
vitreous.  Color  asparagus-green, 
grass-green,  emerald-green,  green- 
ish-white, and  yellowish-green, 
sometimes  raspberry  or  columbine-red  by  transmitted  light.  Streak  uncol- 
ored.  Transparent— translucent.  Sometimes  a  bluish  opalescence  inter- 
nally. Fracture  conchoidal,  uneven. 


Norway,  Me. 


Alexandrite. 


OXYGEN   COMPOUNDS. ANHYDROUS    OXIDES. 


253 


Var.  1.  Ordinary. — Color  pale  green,  being- colored  by  iron.  G-.  =3.597,  Haddam  ;  3 '734, 
Brazil;  3 '689,  Ural,  Rose;  3 '835,  Orenburg,  Kokscharof.  2.  Alexandrite.—  Color  emerald- 
green,  but  columbine-red  by  transmitted  light.  G.  =3-644,  mean  of  results,  Kokscharof. 
Supposed  to  be  colored  by  chrome.  Crystals  often  very  large,  and  in  twins,  like  f.  477, 
either  six-sided  or  six-rayed. 

Comp. — Be A1O4= Alumina  80 '2,  glucina  19 '8= 100.  Iron  is  also  often  present,  though  not 
in  the  transparent  varieties.  Isomorphous  with  chrysolite. 

Pyr.,  etc. — B.  B.  alone  unaltered ;  with  soda,  the  surface  is  merely  rendered  dull.  With 
borax  or  salt  of  phosphorus  fuses  with  great  difficulty.  With  cobalt  solution,  the  powdered 
mineral  gives  a  bluish  color.  Not  acted  upon  by  acids. 

Diff. — Distinguished  by  its  extreme  hardness,  greater  than  that  of  topaz  ;  and  its  infusi- 
bilifcy  ;  also  characterized  by  its  tabular  crystallization,  in  contrast  with  beryl. 

Obs. — In  Brazil  and  also  Ceylon ;  at  Marchendorf  in  Moravia  ;  in  the  Ural ;  in  the  Mourne 
Mts.,  Ireland;  at  Haddam,  Ct.  ;  at  Norway,  Me. 

When  transparent,  and  of  sufficient  size,  chrysoberyl  is  cut  with  facets,  and  forms  a  beauti- 
ful yellowish-green  gem.  If  opalescent,  it  is  usually  cut  en  cabochon. 


(d)  DEUTOXIDES,  RO2. 


Rutile  Group.     Tetragonal, 

CASSITERITE.     Tin  Stone.     Zinnstein,  Zinnerz,  Germ. 

Tetragonal.  0  A  1-i  =  146°  5';  c  =  0-6724.  1  A  1,  pyr.,  =  121°  40'; 
/  A  1  =  133°  34' ;  1-i  A  1-i,  pyr.,  =  133°  31'.  Cleavage  :  J  and  i-i  hardly 
distinct.  Twins:  f.  478,  t winning-plane  \-i\  producing  often  complex 
forms  through  the  many  modifying  planes  ;  sometimes  repeated  parallel  to 
all  the  eight  planes  \-i\  also  f.  480,  a  metagenic  twin.  Often  in  reniform 
shapes,  structure  fibrous  divergent ;  also  massive,  granular  or  impalpable. 


478 


479 


II. =6-7.  Gr.=6*4-7'l.  Lustre  adamantine,  and  crystals  usually  splen- 
dent. Color  brown  or  black  ;  sometimes  red,  gray,  white,  or  yellow. 
Streak  white,  grayish,  brownish.  Nearly  transparent — opaque.  Fracture 
subconchoidal,  uneven.  Brittle. 

Var. — 1.  Ordinary,  Tin- stone.  In  crystals  and  massive.  G.  of  ordinary  cryst.  6 '96;  of 
colorless,  from  Tipuani  R.,  Bolivia,  6 '832,  Forbes.  2.  Wood  Tin  (Holz-Zinn,  Germ.).  In 
botryoidal  and  reniform  shapes,  concentric  in  structure,  and  radiated  fibrous  internally, 


254 


DESCRIPTIVE   MINERALOGY. 


although  very  compact,  with  the  color  brownish,  of  mixed  shades,  looking-  somewhat  like  dry 
wood  in  its  colors.  G-.  of  one  variety  6 '514.  /Stream  tin  is  nothing  but  the  ore  in  the  state 
of  sand,  as  it  occurs  along  the  beds  of  streams  or  in  the  gravel  of  the  adjoining  region. 
It  has  been  derived  from  tin  veins  or  rocks,  through  the  wear  and  decomposition  of  the  rocks 
and  transportation  by  water. 

Comp.— SnO2  =  Tin  78'6,  oxygen  21  '4=100. 

Pyr.,  etc. — B.B.  alone  unaltered.  On  charcoal  with  soda  reduced  to  metallic  tin,  and 
gives  a  white  coating.  With  the  fluxes  sometimes  gives  reactions  for  iron  and  manganese, 
and  more  rarely  for  tantalic  oxide.  Only  slightly  acted  upon  by  acids. 

Diff. — Distinguished  by  its  high  specific  gravity,  its  infusibility,  and  by  its  yielding  metallic 
tin  B.B.  from  some  varieties  of  garnet,  sphalerite,  and  black  tourmaline,  to  which  it  has 
some  resemblance.  Specific  gravity  (6 '5)  higher  than  that  of  rutile  (4). 

Obs. — Tin  ore  is  met  with  in  veins  traversing  granite,  gneiss,  mica  schist,  chlorite  or  clay 
schist,  and  porphyry.  Occurs  in  Cornwall ;  in  Devonshire ;  in  Bohemia  and  Saxony  ;  at 
Limoges  ;  also  in  G-alicia ;  Greenland  ;  Sweden,  at  Finbo  ;  Finland,  at  Pitkaranta.  In  the 
rE.  Indies  ;  in  Victoria  and  New  South  Wales ;  in  large  quantities  in  Queensland.  In  Bolivia, 
S.  A.  ;  in  Mexico. 

In  the  United  States,  rare  :  in  Maine,  at  Paris  ;  in  N.  Hamp.,  at  Lyme ;  in  California,  in 
San  Bernardino  Co.  ;  in  Idaho,  near  Boonville. 


RUTILE. 

Tetragonal.  O  A  l-i  =  147°  12J',  c  =  0-6442.  lAl,  pyr.,  =  123°  TV, 
7"A  1  =  132°  20'.  Cleavage:  /and  i-i,  distinct;  1,  in  traces.  Vertical 
planes  usually  striated.  Crystals  often  acicular.  Twins :  (1)  twinning-plane 
1-e  (see  p.  94).  (2)  3-i,  making  a  wedge-shaped  crystal  consisting  of  two 
individuals.  (3)  l-i  and  3-i  in  the  same  crystal  (fr.  Magnet  Cove,  Ilessen- 
berg).  Occasionally  compact,  massive. 


481 


Graves  Mtn. ,  Ga. 


H.= 6-6*5.  G.— 4-18-4-25.  Lustre  metallic-adamantine.  Color  red- 
dish-brown, passing  into  red  ;  sometimes  yellowish,  bluish,  violet,  black  ; 
rarely  grass-green.  Streak  pale  brown.  Subtransparent — opaque.  Frac- 
ture snbconchoidal,  uneven.  Brittle. 


Comp.,  Var.— Titanic  oxide,  Ti02=Oxygen  39,  titanium  61=100.  Sometimes  a  little  iron 
is  present. 

Pyr.,  etc. — B.B.  infusible.  With  salt  of  phosphorus  gives  a  colorless  bead,  which  in  E.F. 
assumes  a  violet  color  on  cooling.  Most  varieties  contain  iron,  and  give  a  brownish -yellow 
or  red  bead  in  R.F.,  the  violet  only  appearing  after  treatment  of  the  bead  with  metallic  tin 
on  charcoal.  Insoluble  in  acids ;  made  soluble  by  fusion  with  an  alkali  or  alkaline  carbonate. 
The  solution  containing  an  excess  of  acid,  with  the  addition  of  tin-foil,  gives  a  beautiful 
violet-color  when  concentrated. 


OXYGEN   COMPOUNDS. ANHYDROUS    OXIDES. 


255 


Diff. — Characterized  by  its  peculiar  sub-adamantine  lustre,  and  brownish-red  color.  Differs 
from  tourmaline,  vesuvianite,  augite  in  being  entirely  unaltered  when  heated  alone  B.B. 
Specific  gravity  about  4,  cassiterite  6  '5. 

Obs, — Rutile  occurs  in  granite,  gneiss,  mica  slate,  and  syenitic  rocks,  and  sometimes  in 
granular  limestone  and  dolomite.  It  is  generally  found  in  imbedded  crystals,  often  in  masses 
of  quartz  or  feldspar,  and  frequently  in  acicular  crystals  penetrating  quartz.  Very  commonly 
implanted  in  regular  position  upon  crystals  of  hematite,  as  from  Cavradi  in  the  Tavetschthal. 
Occurs  in  Norway ;  Finland  ;  Saualpe,  Carinthia ;  in  the  Urals  ;  in  the  Tyrol ;  at  St.  Gothard ; 
near  Freiberg  ;  at  Ohlapian  in  Transylvania. 

In  Maine,  at  Warren.  In  Vermont,  at  Waterbury  and  elsewhere.  In  Mass. ,  at  Barre ; 
Shelburne;  Sheffield.  In  Conn.,  at  Lane's  mine,  Monroe.  In  N.  York,  in  Orange  Co.; 
Edenville  ;  Warwick.  In  Penn.,  Chester  Co.  In  JV.  Car.,  at  Crowder's  Mountain.  In 
Georgia,  in  Habersham  Co.  ;  in  Lincoln  Co. ,  at  Graves'  Mountain.  In  Arkansas,  at  Magnet 
Cove. 

Titanium  oxide  is  employed  for  a  yellow  color  in  painting  porcelain,  and  also  for  giving  the 
requisite  tint  to  artificial  teeth. 


Binnenthal. 


OOTAHEDRITE.     Anatase. 

Tetragonal.     0  A  \-i  =  119°  22' ;  c  =  1-77771.      Commonly  octahedral 
or  tabular.    1  A  1,  pyr.,  = 
97°  51'.    /Al  =  158°  18'.  484 

Cleavage :   1  and  0,  per- 
fect, 

H, =5-5-6.      G.=3-82- 
3-95;  sometimes  4-11-4-16 
after    heating.      Lustre 
metallic-adamantine.  Col- 
or various  shades  of  brown,  passing  into  indigo-blue, 
and    black ;    greenish-yellow    by    transmitted    light. 
Streak  uncolored.     Fracture  subconchoidal.     Brittle. 

Comp. — Like  rutile  and  brookite,  pure  titanic  oxide. 

Pyr.,  etc. — Same  as  for  rutile. 

Obs. — Abundant  at  Bourg  d'Oisans,  in  Dauphiny ;  also  in  the  Bin- 
nenthal (including  here  Kenngott's  wiserinf,,  f.  484,  as  shown  by  Klein,  Jahrb.Min.,  1875, 
337);    at  Pfitsch   Joch,   Tyrol  ;  near  Hof  in  the  Fichtelgebirge  ;  Norway;    the   Urals;  in 
Devonshire,  near  Tavistock  ;  at  Tremadoc,  in  North  Wales  ;  in  Cornwall ;  in  Brazil  in  quartz. 
In  the  U.  States,  at  Smithfield,  R.  I. 

HAUSMANNITE. — Mn3O4=2MnO,MnO2.     Tetragonal,   0  A  1-i  =130°  25'.      Color  brownish- 
black.     Thuringia  ;  Harz,  etc. 

BRAUNITE.— 2(2MnO,MnO2)+Mn02,SiO>.      Tetragonal,    0Al-a=135°    26'.      Color  dark 
brownish-black.     Thuringia  ;  Norway,  etc. 

MINIUM  (Mennige,  Germ.).— Pb3O4=Pb02+2PbO.     Badenweiler;  Wythe  Co.,  Va.,  etc. 


BROOKITE. 

Orthorhombic  (?).  /A  7=99°  50'  (-100°  50'):  O  A  14  =  131°  42'; 
c\l:d  =  1-1620  :  1-1883  :  1.  Cleavage :  /,  indistinct ;  0,  still  more  so. 

H.  =  5-5-6.  G.=4-12-4-23, brookite;  4-03-4-085,  arkansite.  Hair-brown, 
yellowish,  or  reddish,  with  metallic  adamantine  lustre,  and  translucent 


256 


DESCRIPTIVE   MINERALOGY. 


(brookite);  also  iron-black,  opaque,  and   submetallic   (arkansite).     Streak 
uncolored — grayish,  yellowish.     Brittle. 


487 


488 


Arkansas. 


if 


Ellenville,  N.  Y. 


Miask,  Ural. 


Comp — Pure  titanic  oxide,  Ti02,  like  rutile  and  octahedrite. 

Pyr.,  etc. — Same  as  for  rutile. 

Obs — Brookite  occurs  at  Bourg  d'Oisans  in  Dauphiny  ;  at  St.  Gothard ;  in  the  Urals,  near 
Miask  ;  in  thick  black  crystals  (arkamite  f.  486)  at  Magnet  Cove,  Arkansas,  sometimes  altered 
to  rutile  by  paramorpfmm ;  at  Ellenville,  Ulster  Co.,  N.  Y.  ;  at  Paris,  Maine. 

Schrauf  has  announced  (Atlas  Mia.,  Reich.  IV.)  that  he  has  found  brookite  to  be  monocUnic 
(and  isomorphous  with  wolframite).  He  distinguishes  three  types  having  different  axial 
relations.  The  measurements  of  v.  Rath,  however,  seem  to  show  that  in  part  it  must  be 
ortJioihombic. 

EUMANITE. — From  Chesterfield,  Mass.,  may  be  identical  with  brookite.1 


Orthorhombic. 


489 


PYROLUSITE.    Polianite. 

/A/=  93°  40',  OM-l  =  142°  11';  c  :  I  :  a  =  O776  : 
1-066  :  1.  Cleavage  /and  i-L  Also  columnar,  often 
divergent ;  also  granular  massive,  and  frequently  in 
reniform  coats.  Often  soils. 

H.=2-2-5.  G.=4-82.  Turner.  Lustre  metallic. 
Color  iron-black,  dark  steel-gray,  sometimes  bluish. 
Streak  black  or  bluish-black,  sometimes  submetallic. 
Opaque.  Rather  brittle. 


Comp. — MnO2=Manganese  63'2,  oxygen  36 '8=100. 

Pyr.,  etc. — B.B.  alone  infusible;  on  charcoal  loses  oxygen.  A  manganese  reaction  with 
borax.  Affords  chlorine  with  hydrochloric  acid. 

Diff. — Hardness  less  than  that  of  psilomelane.  Differs  from  iron  ores  in  its  reaction  for 
manganese  B.  B.  Easily  distinguished  from  psilomelane  by  its  inferior  hardness,  and  usually 
by  being  crystalline. 

Obs. — Occurs  extensively  at  Elgersberg  near  Ilmenau  in  Thuringia ;  at  Vorderehrensdorf  in 
Moravia ;  at  Platten  in  Bohemia,  and  elsewhere.  Occurs  in  the  United  States  in  Vermont, 
at  Brandon,  etc.  ;  at  Conway,  Mass.  ;  at  Winchester,  N".  H.  ;  at  Salisbury  and  Kent,  Conn. 
In  California,  on  Red  island,  bay  of  San  Francisco.  In  New  Brunswick,  near  Bathurst.  In 
Nova  Scotia,  at  Walton ;  Pictou,  etc. 

Pyrolusite  and  manganite  are  the  most  important  of  the  ores  of  manganese.  Pyrolusite 
parts  with  its  oxygen  at  a  red  heat,  and  is  extensively  employed  for  discharging  the  brown 
and  green  tints  of  glass.  It  hence  received  its  name  from  nvp,  fire,  and  Aiw,  to  wash. 

CREDNERITE. — Cu3Mn<2O9,  or  3CuO 4-2Mn03.     Foliated.     Color  black.     Thuringia. 


OXYGEN    COMPOUNDS. HYDROUS    OXIDES. 


257 


B.  HYDROUS    OXIDES. 


TURGITE. 

Compact  fibrous  and  divergent,  to  massive ;  often  botryoidal  and  sta- 
lactitic  like  limonite.  Also  earthy,  as  red  ochre. 

.  H.=:5-6.  G.  =  3-56-3-74,  from  Ural;  4-29-4-49,  fr.  Hof;  4-681,  fr. 
Horhausen ;  4*14,  fr.  Salisbury.  Lustre  submetallic  and  somewhat  satin- 
like  in  the  direction  of  the  fibrous  structure;  also  dull  earthy.  Color 
reddish-black,  to  dark  red ;  bright-red  when  earthy ;  botryoidal  surface 
often  lustrous,  like  much  lirnonite.  Opaque. 

Comp. — HoFevjOT^Iron  sesquioxide  94 '7,  water  5 '3=100. 

Pyr.,  etc. —  Heated  in  a  closed  tube,  flies  to  pieces  in  a-remarkable  manner  ;  yields  water. 
Otherwise  like  hematite. 

Diff. — Distinguished  from  hematite  and  limonite  by  its  superior  hardness,  the  color  of  its 
streak,  and  B.B.  its  decrepitation. 

Obs. — A  very  common  ore  of  iron.  Occurs  at  the  Turginsk  copper  mine  near  Bosgolovsk, 
in  the  Ural ;  near  Hof  in  Bavaria,  and  Siegen  in  Prussia  ;  at  Horhausen.  In  the  U.  S.  it 
occurs  at  Salisbury,  Ct. 


DIASPORE. 


Orthorhombic.       /A  /=  93°    42f,     0 A 14=  147°    12*' 
0-64425  :  1-067  :  1.      i4M.-l  =  121°  7-i',    *-*Al-2  =  104°  " 
14|',   i-lM  =  116°  54^.      Crystals  usually  thin,  flattened 
pa.rallel  to  i-l\   sometimes  acicular;  commonly  implanted. 
Cleavage  :  i-%  eminent ;  i-2  less  perfect.     Occurs  foliated 
massive  and  in  thin  scales ;  sometimes  stalactitic. 

II.  =  6-5-7.  G.  =  3-3-3-5.  Lustre  brilliant  and  pearly  on 
cleavage-face ;  elsewhere  vitreous.  Color  whitish,  grayish- 
white,  greenish-gray,  hair-brown,  yellowish,  to  colorless ; 
sometimes  violet-blue  in  one  direction,  reddish  plumb-blue 
in  another,  and  pale  asparagus-green  in  a  third.  When  thin, 
translucent — subtranslucent.  Very  brittle. 

Comp. — H2A104= Alumina  85'1,  water  14'9=100 ;  a  little  phosphorus 
pentoxide  is  often  present. 

Pyr.,  etc. — In  the  closed  tube  decrepitates  strongly,  separating  into  pearly  white  scales, 
and  at  a  high  temperature  yields  water.  The  variety  from  Schemnitz  does  not  decrepitate. 
Infusible  ;  with  cobalt  solution  gives  a  deep  blue  color.  Some  varieties  react  for  iron  with 
the  fluxes.  Not  attacked  by  acids,  but  after  ignition  becomes  soluble  in  sulphuric  acid. 

Diff. — Distinguished  (B.B.)  by  its  decrepitation  and  yielding  water  ;  as  also  by  the  reaction 
for  alumina  with  cobalt  solution.  Resembles  some  varieties  of  hornblende,  but  is  harder. 

Ob?. — Commonly  found  with  corundum  or  emery.  Occurs  in  the  Ural ;  at  Schemnitz ; 
at  Broddbo  near  Fahlun;  in  Switzerland  ;  in  Asia  Minor,  and  the  Grecian  islands  ;  in  Chester 
Co.,  Pa.  ;  at  the  emery  mines  of  Chester,  Mass.  ;  N.  Carolina. 

Diaspore  was  named  by  Haiiy  from  diaGireipu,  to  scatter,  alluding  to  the  usual  decrepitation 
before  the  blowpipe. 

17 


258 


DESCRIPTIVE   MINERALOGY. 


iz 


GOTHITE. 

Orthorhombic.     /A  7=  94°  52'  (B.  &  M.) ;   O  A  14  =  146°  33' ;  c  :  2  :  a 
=  0*66  :  1*089  :  1.     In    prisms   longitudinally  striated,  and 
491  often  flattened  into  scales  or  tables  parallel  to  the  shorter 

diagonal.  Cleavage :  braehydiagonal,  very  perfect.  Also 
fibrous;  foliated  or  in  scales;  massive;  renif  orm ;  stalac- 
titic. 

EL  — 5-5*5.  G.=4r'0-4:vi.  Lustre  imperfect  adamantine. 
Color  yellowish,  reddish,  and  blackish-brown.  Often  blood- 
red  by  transmitted  light.  Streak  brownish-yellow — ochre- 
yellow. 

Var. — 1.  In  thin  scale-like  or  tabular  crystals,  usually  attached  by  one 

edge.  2.  In  acicular  or  capillary  (not  flexible)  crystals,  or  slender  prisms,  often  radiately 
grouped  :  the  Needle- Ironstone  (Nadelei^enstein}.  It  passes  into  (b)  a  variety  with  a  velvety 
surface :  the  Przibramite  (Sammetblende}  of  Przibram  is  of  this  kind.  Other  varieties  are 
columnar  or  fibrous,  scaly-fibrous,  or  feathery  columnar;  compact  massive,  with  a  flat  con- 
choidal  fracture  ;  and  sometimes  reniform  or  stalactitic. 

Comp.— H,FeO4=H6FeOe-l-2Fep3== Iron  sesquioxide  89 '9,  water  KM=100. 

Pyr.,  etc. — In  the  closed  tube  gives  off  water  and  is  converted  into  red  iron  sesquioxide. 
With  the  fluxes  like  hematite ;  most  varieties  give  a  manganese  reaction,  and  some  treated 
in  the  forceps  in  O.F.,  after  moistening  in  sulphuric  acid,  impart  a  bluish-green  color  to  the 
flame  (phosphoric  acid).  Soluble  in  hydrochloric  acid. 

Obs. — Found  with  the  other  iron  oxides,  especially  hematite  or  limonite.  Occurs  at  Eiser 
feld  ;  in  Nassau ;  at  Zwickaii  in  Saxony ;  in  Cornwall ;  in  Somersetshire,  at  the  Providence 
iron  mines.  In  the  U.  States,  near  Marquette,  L.  Superior;  in  Penn.,  near  Easton ;  in 
California,  at  Burns  Creek,  Mariposa  Co. 

Named  GotJiite  after  the  poet-philosopher  G-othe ;  and  PyrrJwsiderite  from  irvppoc,  fire-red, 
.and  aidijpoc,  iron. 

MANGANITE. 

Orthorhombic.  /A  1=  99°  40',  0  A.  l-l  =  147°  9£' ;  c:l:&  =  0'6455  : 
1*185  :  1.  Twins:  twinn ing-plane  \-l  (f.  296,  p.  96).  Cleavage:  i-%  very 
perfect,  7  perfect.  Crystals  longitudinally  striated,  and  often  grouped  in 
bundles.  Also  columnar ;  seldom  granular ;  stalactitic. 

H.  =  4r.  G.=4r*2— 4'4r.  Lustre  submetallic.  Color  dark  steel-gray — iron- 
black.  Streak  reddish-brown,  sometimes  nearly  black.  Opaque ;  minute 
splinters  sometimes  brown  by  transmitted  light.  Fracture  uneven. 

Comp.— H.2Mn04=H6MnOe  +  2Mn03=Manganese  sesquioxide  89'8  (=Mn  62'5,  0  27 '3), 
water  10-2=100. 

Pyr.,  etc. — In  the  closed  tube  yields  water  ;  otherwise  like  braunite. 

Obs. — Occurs  in  veins  traversing  porphyry,  at  Ilefeld  in  the  Harz  ;  in  Thuringia  ;  Undenaes 
in  Sweden ;  Christiansand  in  Norway ;  Cornwall,  at  various  places ;  also  in  Cumberland, 
Devonshire,  etc.  In  Nova  Scotia,  af  Cheverie,  etc.  In  New  Brunswick,  at  Shepody  moun- 
tain, Albert  Co.,  etc. 


LIMONITE.     Brown  Hematite.     Brauneisenstein,  Germ. 

Usually  in  stalactitic  and  botryoidal  or  mammillary  forms,  having  a  fibrous 
or  subfibrous  structure;  also  concretionary,  massive;  and  occasionally 
earthy. 


OXYGEN    COMPOUNDS. — HYDROUS    OXIDES.  259 

H.r=  5-5*5.  G.  — 3'6-4.  Lustre  silky,  often  submetallic  ;  sometimes  dull 
and  earthy.  Color  of  surface  of  fracture  various  shades  of  brown,  com- 
monly dark,  and  none  bright ;  sometimes  with  a  nearly  black  varnish-like 
exterior ;  when  earthy,  brownish-yellow,  ochre-yellow*  Streak  yellowish- 
brown. 

Var. — (1)  Compact.  Submetallic  to  silky  in  lustre  ;  often  stalactitic,  botryoidal,  etc.  (2) 
Ochreous  or  earthy,  brownish -yellow  to  ochre-yellow,  often  impure  from  the  presence  of  clay, 
sand,  etc.  (3)  Bog  ore.  The  ore  from  marshy  places,  generally  loose  or  porous  in  texture, 
often  petrifying  leaves,  wood,  nuts.  etc.  (4)  Brown  clay -ironstone,  in  compact  masses,  often 
in  concretionary  nodules,  having  a  brownish-yellow  streak,  and  thus  distinguishable  from  the 
clay- ironstone  of  the  species  hematite  and  siderite ;  it  is  sometimes  (a)  pisolitic,  or  an  aggre- 
gation of  concretions  of  the  size  of  small  peas  (Bohnerz,  Germ. ) ;  or  (b}  oolitic. 

Comp.— H6Fe,O9  =  H6FeOo  +  FeO3=Iron  sesquioxide  85 '6,  water  14 '4=100.  In  the  bog 
ores  and  ochres,  sand,  clay,  phosphates,  manganese  oxides,  and  humic  or  other  acids  of  organic 
origin  are  very  common  impurities. 

Pyr.,  etc. — Like  gothite.  Some  varieties  give  a  skeleton  of  silica  when  fused  with  salt  of 
phosphorus,  and  leave  a  siliceous  residue  when  attacked  by  acids. 

Diff. — Distinguished  from  hematite  by  its  yellowish  streak,  inferior  hardness,  and  its  reac- 
tion for  water.  Does  not  decrepitate,  B.B.,  like  turgite. 

Obs. — Limonite  occurs  in  secondary  or  more  recent  deposit55,  in  beds  associated  at  times 
with  barite,  siderite,  calcite,  aragonite,  and  quartz  ;  and  often  with  ores  of  manganese ;  also 
as  a  modern  marsh  deposit.  It  is  in  all  cases  a  result  of  the  alteration  of  other  ores,  through 
exposure  to  moisture,  air,  and  carbonic  or  organic  acids ;  and  is  derived  largely  from  the 
change  of  pyrite,  siderite,  magnetite,  and  various  mineral  species  (such  as  mica,  augite,  horn- 
blende, etc.  \  which  contain  iron  in  the  protoxide  state. 

Abundant  in  the  United  States.  Extensive  beds  exist  at  Salisbury  and  Kent,  Conn. ,  also 
in  the  neighboring  towns  of  N.  Y.,  and  in  a  similar  situation  north;  at  Richmond  and  Lenox, 
Mass.  ;  in  Vermont,  at  Bennington,  etc. 

Limonite  is  one  of  the  most  important  ores  of  iron.  The  pig  iron,  from  the  purer  varieties, 
obtained  by  smelting  with  charcoal,  is  of  superior  quality.  That  yielded  by  bog  ore  is  what 
is  termed  cold  short,  owing  to  the  phosphorus  present,  and  cannot  therefore  be  employed  in 
the  manufacture  of  wire,  or  even  of  sheet  iron,  but  is  valuable  for  casting.  The  hard  and 
compact  nodular  varieties  are  employed  in  polishing  metallic  buttons,  etc. 

MELANOSIDERITE. — Near  limonite,  but  containing  7 '39  p.  c.  SiO2,  perhaps  as  an  impurity. 
Cooke  regards  it  as  a  very  basic  silicate  of  iron.  G.  =3*39.  Westchester,  Penn. 

XANTHOSIDERITE.—  H4FeO5=Fe03  81 '6,  H2O  18 '4=100  ;  or  H6FeO6  (Eamm.).  In  fine 
needles.  Color  yellow,  brown.  Ilmenau  ;  the  Harz. 

BEAUXITE. — Occurs  in  concretionary  grams.  Color  whitish  to  brown.  Composition  doubt- 
ful, perhaps  Al(Fe)O3+2aq.  Beaux,  near  Aries,  France  ;  near  Lake  Wochein,  Styria  (wochei- 
nite) ;  French  Guiana. 


BRUCITE. 


Rhombohedral.      E  A  R  =  82°  22£',    O/\fi  =  ll9°  39£' ;    c  =  1-52078 
(Heseeiiberg).     Crystals   often   broad  tabular.     Cleavage :  basal,  eminent, 


Low's  Mine,  Texas.  Wood's  Mine,  Texas. 

folia  easily  separable,  nearly  as  in  gypsum.     Usually  foliated   massive. 
Also  fibrous,  fibres  separable  and  elastic. 


260  DESCRIPTIVE   MINEEALOGY. 

H.  =  2'5.  G.—  2-35-2-44:.  Lustre  pearly  on  a  cleavage-face,  elsewhere 
between  waxy  and  vitreous ;  the  fibrous  silky.  Color  white,  inclining  to 
gray,  blue,  or  green.  Streak  white.  Translucent — subtranslucent.  Sectile. 
Thin  laminae  flexible. 

Comp.— H2Mg02— Magnesia  69,  water  31  =  100. 

Var. — 1.  Foliated.     2.  Fibrous  ;  called  nemalite,  containing-  4  or  5  p:  c.  of  FeO. 

Pyr.,  etc. — In  the  closed  tube  gives  off  water,  becoming  opaque  and  friable,  sometimes 
turning  gray  to  brown.  B.  B.  infusible,  glows  with  a  bright  light,  and  the  ignited  mineral 
reacts  alkaline  to  test  paper.  With  cobalt  solution  gives  the  violet-red  color  of  magnesia. 
The  pure  mineral  is  soluble  in  acids  without  effervescence. 

Diff.  —Distinguished  by  its  infusibility.     Differs  from  talc  in  its  solubility  in  acids. 

Obs. — Brucite  accompanies  other  magnesian  minerals  in  serpentine,  and  has  also  been  found 
in  limestone.  Occurs  at  Swinaness  in  Unst,  Shetland  Isles ;  in  the  Urals  ;  at  Goujot  in 
France  ;  near  Filipstadt  in  Wermland.  It  occurs  at  Hoboken,  N.  J.  ;  in  Richmond  Co. ,  N.  Y. ; 
at  Brewster,  N.  Y.  ;  at  Texas,  Pa.  The  fibrous  variety  (nemalite}  occurs  at  Hoboken,  and 
at  Xettes  in  the  Vosges. 

GIBBSITE. 

Monoclinic  (DesCL).  In  small  hexagonal  crystals  with  replaced  lateral 
edges.  Planes  vertically  striated.  Cleavage  :  basal  or  O  eminent.  Occa- 
sionally in  lamello-radiate  spheroidal  concretions.  Usually  stalactitic,  or 
small  mammillary  and  incrusting,  with  smooth  surface,  and  often  a  faint 
fibrous  structure  within. 

II. =2-5-3-5.  Gr.  =  2-3-2-4.  Color  white,  grayish,  greenish,  or  reddish- 
white  ;  also  reddish-yellow  when  impure.  Lustre  of  O  pearly  ;  of  other 
faces  vitreous ;  of  surface  of  stalactites  faint.  Translucent ;  sometimes 
transparent  in  crystals.  A  strong  argillaceous  odor  when  breathed  on. 

Tough. 

• 

Var. — 1.  In  crystals:  the  original  hydrargillite.     2.  Stalactitic;  gibbsite. 

Comp.— H6  A1O6-- Alumina  65-5,  water  34  5  =  100. 

Pyr.,  etc. —  In  the  closed  tube  becomes  white  and  opaque,  and  yields  water.  B.B.  infusible, 
whitens,  and  does  not  impart  a  green  color  to  the  flame.  With  cobalt  solution  gives  a  deep- 
blue  color.  Soluble  in  concentrated  sulphuric  acid. 

Diff.  --Resembles  chalcedony  in  appearance,  but  is  softer. 

Obs. — The  crystallized  gibbsite  occurs  near  Slatoust  in  the  Ural ;  at  Grumuchdagh,  Asia 
Minor;  on  corundum  at  Union ville,  Pa.;  in  Brazil.  The  stalactitic  occurs  at  Richmond, 
Mass.;  at  the  Clove  mine,  Duchess  Co.,  N.  Y.;  in  Orange  Co.,  N.  Y. 

Rose's  hydrargillite  (Urals,  1839)  is  identical  with  gibbsite  (Torrey,  1822),  and  must  receive 
this  name.  An  uncertain  mineral  from  Richmond  afforded  Hermann  38  p.  c.  of  phosphoric 
acid,  but  a  phosphate,  if  it  really  occurs  there,  is  not  gibbsite. 

PYROCHROITE. — H2MnO2=Manganese  protoxide  79'8,  water  20-2=100.  Foliated.  Color 
white.  Mine  of  Paisberg,  Filipstadt,  Sweden. 

HYDROTALCITE  from  Snarum,  Norway,  and  VOLKNERITE  from  the  Urals,  contain  alumina, 
magnesia,  and  water  with  more  or  less  carbon  dioxide.  Probably  mixtures,  containing 
brucite,  gibbsite,  etc.  HOUGHITE  from  Oxbow  and  Rossie,  N.  Y.,  is  a  similar  mineral 
derived  from  the  alteration  of  spinel.  NAMAQUALITE  ( Church] .  A  related  mineral ;  from 
Namaqualand,  So.  Africa. 


PSILOMELANE. 


Massive  and  botryoidal.     Reniform.     Stalactitic. 

Ii.=:5-6.     G.:=3'7-4'7.     Lustre    submetallic.     Streak    brownish-black, 
shining.     Color  iron-black,  passing  into  dark  steel-gray.     Opaque. 


OXYGEN   COMPOUNDS. HYDROUS   OXIDES.  261 

Oomp. — Somewhat  doubtful.  Contains  manganese  oxide,  with  varying  amounts  of  baryta, 
and  potash  (lithia),  and  also  water.  General  formula,  according  to  Rammelsberg,  R6O9=RO 
+4Mn02,  where  R  is  Ka2,  Ba  or  Mn.  Analyses: 

O        MnO      BaO       K2O       H2O 

1.  Thuringen    11 -43    65'76     16'59      5-25     CuO  0-59,  CoO  0'79,  CaO  0'51  =  100-72 

Olschewsky. 

2.  Ilmenau        15 '82    77'23      0'12      5'29      CaO  0'91,  CuO  0'40=99'77  Clausbruch. 

Pyr.,  etc. — In  the  closed  tube  most  varieties  yield  water,  and  all  lose  oxygen  on  ignition ; 
with  the  fluxes  reacts  for  manganese.  Soluble  in  hydrochloric  acid,  with  evolution  of 
chlorine. 

Ob.* — This  is  a  common  ore  of  manganese.  It  occurs  in  Devonshire  and  Cornwall ;  at 
Ilefeld  in  the  Harz ;  also  at  Johanngeorgenstadt ;  Schneeberg  ;  Ilmenau ;  Siegen,  etc.  It 
forms  mammillary  masses  at  Chittenden,  Irasburg,  and  Brandon,  Vt. 


WAD. 

The  manganese  ores  here  included  occur  in  amorphous  and  reniform 
masses,  either  earthy  or  compact,  and  sometimes  incrusting  or  as  stains. 
They  are  mixtures  of  different  oxides,  and  cannot  be  considered  chemical 
compounds  or  distinct  mineral  species. 

II.  =  0-5-6.  G.  =  3-4-26  ;  often  loosely  aggregated,  and  feeling  very  light 
to  the  hands.  Color  dull  black,  bluish  or  brownish-black. 

Comp.,  Var. — Perhaps  H2Mn2O6=2Mn02+aq  (Rammelsberg),  but  in  all  cases  mixed  with 
other  ingredients. 

Varieties  :  (A)  Manganesian  ;  (B)  Cobaltiferous  ;  (C)  Cupriferous. 

A.  BOG  MANGANESE. — Consists  mainly  of  manganese  dioxide  and  water,  with  some  iron 
sesquioxide,  and  often  silica,  alumina,  baryta. 

B.  ASBOLITE,  or  Earthy  Cobalt,  is  wad  containing  cobalt  oxide,  which  sometimes  amounts 
to  32  p.  c.     LithiopJwrite,  heterogenite,  and  rabdionite  belong  near  here. 

C.  LAMPADITE,  or  Cupreous  Manganese.     A  wad  containing  4  to  18  p.  c.  of  copper  oxide, 
and  often  cobalt  oxide  also.     It  graduates  into  black  copper  (Melaconite).     G.  =3'l-3'2. 

Pyr.,  etc. —  Wad  reacts  like  psilomelane.  Earthy  cobalt  gives  a  blue  bead  with  salt  of 
phosphorus,  and  when  heated  in  R.  F.  on  charcoal  with  tin,  some  specimens  yield  a  red  opaque 
bead  (copper).  Cupreous  manganese  gives  similar  reactions,  and  three  varieties  give  a  strong 
manganese  reaction  with  soda,  and  evolve  chlorine  when  treated  with  hydrochloric  acid. 

Obs. — The  above  ores  are  results  of  the  decomposition  of  other  ores — partly  of  oxides,  and 
partly  of  manganesian  carbonates.  Wad  or  bog  manganese  is  abundant  in  the  counties  of 
Columbia  and  Dutchess,  N.  Y.  There  are  large  deposits  of  bog  manganese  at  Blue  Hill  Bay, 
Dover,  and  other  places  in  Maine. 

Earthy  cobalt  occurs  at  Riechelsdorf  in  Hesse;  Saalfeld  in  Thuringia;  at  Nertschinsk  in 
Siberia ;  at  Alderly  Edge  in  Cheshire. 

CHALCOPHANITE. — Rhombohedral.  In  druses  of  minute  tabular  crystals  ;  also  in  stalacti- 
tic  aggregates.  H.  =2'5.  Gr.  —  3 '907.  Lustre  metallic.  Color  bluish-black.  'Analysis  gave 
MnO2  59-94,  MnO  6 -58,  ZnO  21 '70,  FeO3  0'25,  H.O  11 -58  =  100-05.  Composition  2MnO2  + 
(Mn,ZnjO+2aq.  If  half  the  water  were  basic,  the  formula  might  be  written  2(R,Mn)O3+aq, 
where  R=Mn,Zn  and  H2.  B.B.  becomes  of  a  copper  color,  hence  the  name  (xoAicds,  brass, 
bronze,  and  4>cuVw,  to  appear).  Stirling  Hill,  N.  J.  (Moore.) 


262 


DESCRIPTIVE   MINERALOGY. 


2.  OXIDES  OF  ELEMENTS  OF  THE  ARSENIC  AND  SULPHUR  GROUPS,  SERIES  II. 

VALENTINITE.    Weisspiesglaserz,  Germ. 

Orthorhombic.  /A  7  =  136°  58' ;  0  A  l-l  =  105°  35' ;  c  :  I  :  a  =  3-5868  : 
2*5365  :  1.  Often  in  rectangular  plates  with  the  lateral 
edges  bevelled,  and  in  acicular  rhombic  prisms.  Cleav- 
age :  /,  highly  perfect,  easily  obtained.  Also  massive  ; 
structure  lamellar,  columnar,  graimlar. 

H.=r2-5-3.  G.  =  5-566,  crystals  from  Braunsdorf. 
Lustre  adamantine,  i-l  often  pearly  ;  shining.  Color 
snow-white,  occasionally  peach-blossom  red,  and  ash-gray 
to  brownish.  Streak  white.  Translucent — subtrans- 
parent. 


Comp.— SbaOs=Oxygon  16 '44,  antimony  83 '56  =  100. 
Ob^. — Found  at  Przibram  in  Bohemia;  at  Felsobanya  in  Hungary; 
Braunsdorf  in  Saxony.     Also  at  South  Ham,  Canada  East. 

SENARMONTITE. — Same  composition  as  the  above,  but  crystallizes  in  isometric  octahe- 
drons. Gr.=5'2-5'3.  Perneck,  Hungary ;  Cornwall;  Haraclas  in  Algeria  ;  S.  Ham,  Canada. 

CLAUDETITE  ;  ARSENOLITE. — Both  As2O3.  The  former  is  orthorhombic,  the  latter  iso- 
metric. They  thus  correspond  to  the  two  forms  of  Sb2O3  (see  above).  Claudetite  (G-.  =3'85) 
occurs  in  thin  plates  at  the  San  Domingo  mines,  Portugal.  Arsenolite  (G.= 3  '698)  occurs 
usually  in  capillary  crystals,  also  stalactitic  ;  earthy.  Andreasberg  ;  Joachimsthal ;  Corn- 
wall ;  Ophir  mine,  Nevada ;  California. 

BISMITE  (Wismuthocker,  Germ  ). — Bi2O3.  Occurs  massive,  earthy.  Schneeberg  ;  Joachims- 
thai;  Cornwall.  KARELINITE. — 3BiO+BiS.  Massive.  Color  lead-gray.  G.  =6'60.  Savo- 
dinsk  mine  in  the  Altai. 

MOLYBDITE  (Molybdanocker,  Germ.}. — Composition  Mo03.  In  radiated  crystallizations,  as 
an  incrustation,  etc.  Occurs  with  molybdenite.  At  Westmoreland,  New  Hampshire  ;  Chester, 
Penn.  ;  Virginia  City,  Nevada.  ILSEMANNITE,  near  the  above.  Bleiberg.  Carinthia. 

TUNGSTITE. — WO3.  Pulverulent  and  earthy.  Cornwall;  Monroe,  Ct.  MEYMACITE 
(Carnot). — A  hydrated  tungstite.  Meymac,  Correze. 

KERMESITE  (Anbimonblende,  Germ.}. — Composition  SbaSsO^SbsSs  +  SbsOs.  In  capillary 
crystals.  Color  cherry-red.  Braunsdorf,  Saxony  ;  Allemont ;  South  Ham,  Canada  East. 

CERVANTITE. — SbOa^SbaOs  +  Sb-jOs.  Color  yellow.  Results  from  alteration  of  stibnite. 
Spain ;  Tuscany  ;  Hungary,  etc. ;  South  Ham,  Canada. 


3.  OXIDES  OF  THE  CAKBON-SILICON  GKOUP,  SERIES  II. 


QUARTZ. 

Rhombohedral,  and  for  the  most  part  hemihedral  to  the  rhombohedron 
(or  tetartohedral  to  the  hexagonal  prism).  H  A  R  —  94°  15',  O  A  R  —  128° 
13r;  c  =  1-0999.  i  A  SJ-2  =  142°  2X,  R  A  — l.ov.*,  =  103°  34',  R  A  — 1,  adj., 
=  133°  44',  R  A  i,  ov.  2-2,  =  113°  87.  Cleavage :  E,  —  1,  and  i  very  indis- 
tinct: sometimes  effected  by  plunging  a  heated  crystal  in  cold  water. 
Crystals  sometimes  very  short,  but  general  habit  prismatic  j  the  crystals 


OXYGEN   COMPOUNDS SILICA. 


263 


much  elongated,  sometimes  fine  acicular;  usually  implanted  by  one 
extremity  of  the  prism.  Prismatic  faces  i  commonly  striated  horizontally, 
and  thus  distinguishable,  in  distorted  crystals,  from  the  pyramidal.  Crys- 
tals often  grouped  by  juxtaposition,  not  proper  twins.  Frequently  in  radi- 
ated masses  with  a  surface  of  pyramids,  or  in  druses  having  a  surface  of 
pyramids  or  short  crystals,  ^wins :  t winning-plane,  (1),  the  basal  plane 
O  (f .  506) ;  very  generally  penetration-twins,  as  illustrated  in  f.  265,  p.  89. 
(2)  The  pyramid  1-2,  truncating  the  edge  between  -\-R  and  —  R,  divergence 
of  axes  84°  33',  Other  methods  of  twinning  rare,  parallel  to  i,  to  jR,  to 

503 


501 


502 


£7?,  etc.   (Jenzsch).     Also  in  pseudo-trillings  on  calcite,  with  2-2  as  the 
approximate  twinn ing-plane  (see  f.  336,  p.  101). 

Massive;    coarse    or   fine   granular   to   flint-like   or   crypto-crystallme. 
Sometimes  maminillary,  stalactitic,  and  in  concretionary  forms. 


504 


505 


506 


H.=7.  G.— 2-5-2-8;  2-6413-2-6541  (Beudant).  Lustre  vitreous,  some- 
times inclining  to  resinous  ;  splendent— nearly  dull.  Colorless  when  pure ; 
often  various  shades  of  yellow,  red,  brown,  green,  blue,  black.  Streak 
white,  of  pure  varieties;  if  impure,  often  the  same  as  the  color,  but  much 
paler.  Transparent— opaque.  Fracture  perfect  conchoidal— subconchoi- 
dal.  Tough— brittle— friable.  Polarization  circular,  see  pp.  138-140. 


264  DESCRIPTIVE   MINERALOGY. 

Comp. — Pure  silica,  or  Si02=Oxygen  53 '33,  silicon  46  "67 =100.  In  massive  varieties  often 
mixed  with  a  little  opal-silica.  Impure  varieties  contain  iron  sesquioxide,  calcium  carbonate,, 
clay,  sand,  and  various  minerals. 

Var.— I.  Crystallized  (phenocrystalline),  vitreous  in  lustre.  2.  Flint-like,  massive,  or  cryp- 
tocrystalline.  The  first  division  includes  all  ordinary  vitreous  quartz,  whether  having  crys- 
talline faces  or  not.  The  varieties  under  the  second  are  in  general  acted  upon  somewhat  more 
by  attrition,  and  by  chemical  agents,  as  fluohydric  acid,  than  those  of  the  first.  In  all  kinds 
made  up  of  layers,  as  agate,  successive  layers  are  unequally  eroded. 

A.  PHENOCRYSTALLINE  OR  VITREOUS  VARIETIES. 

1.  Ordinary  Crystallized  ;  Rock  Crystal.     Colorless  quartz,  or  nearly  so,  whether  in  dis- 
tinct crystals  or  not. 

2.  Asteriated  ;  Star  quartz  (Sternquartz,  Germ.}.     Containing  within  the  crystal  whitish 
or  colored  radiations  along  the  diametral  planes. 

3.  Amethystine;  Amethyst.     Clear  purple,  or  bluish -violet.     The  color  is  supposed  to  be 
due  to  manganese. 

4.  nose.     Rose-red  or  pink,  but  becoming  paler  on  exposure.     Common  massive,  and  then 
usually  much  cracked.     Lustre  sometimes  a  little  greasy.     Fuchs  states  that  the  color  is  due 
to  titanic  oxide.     It  may  come  in  part  from  manganese. 

5.  Yellow  ;  False  Topaz.     Yellow  and  pellucid,  or  nearly  so  ;  resembling  somewhat  yellow 
topaz,  but  very  different  in  crystallization  and  in  absence  of  cleavage. 

6.  Smoky,  Cairngorm  Stone.     Smoky -yellow  to  smoky-brown,  and  often  transparent ;  but 
varying  to  brownish- black,  and  then  nearly  opaque  in  thick  crystals.       The  color  is  due   to 
organic  compounds,  according  to  Forster. 

7.  Milky.     Milk-white  and  nearly  opaque.     Lustre  often  greasy,  and  then  called  Greasy 
quartz. 

8.  Caps  Eye  (Katzenauge,  Germ.}.     Exhibiting  opalescence,  but  without  prismatic  colors, 
an  effect  due  to  fibres  of  asbestus. 

9.  Aventurine.     Spangled  with  scales  of  mica  or  other  mineral. 

10.  Impure  from  the  presence  of  distinct  minerals  distributed  densely  through  the  mass. 
The  more  common  kinds  are  those  in  which  the  impurities  are  :   (a)  ferruginous,  either  red  or 
yellow  iron  oxide;   (b}  chioritic,  some  kind  of  chlorite  ;  (c)  actinolitic  ;  (d)  micaceous ;  (e)  are- 
naceous, or  sand.     Quartz  crystals  also  occur  penetrated  by  various  minerals,  as  topaz,  corun- 
dum, chrysoberyl,  garnet,  different  species  of   the  hornblende  and  pyroxene  groups,  rutile, 
hematite,  gothite,  etc.,  etc. 

Containing  liquids  in  cavities.  These  liquids  are  seen  to  move  with  the  change  of  position 
of  the  crystal,  provided  an  air-bubble  be  present  in  the  cavity.  The  liquid  is  either  water 
(pure,  or  a  mineral  solution),  carbon  dioxide,  or  some  petroleum-like  or  other  compound. 

B.  CRYPTOCRYSTALLINE  VARIETIES. 

1.  Chalcedony.     Having  the  lustre  nearly  of  wax,  and  either  transparent  or  translucent. 
Color  white,  grayish,  pale-brown  to  dark-brown,  black  ;  tendon-color  common  ;  sometimes  deli- 
cate blue.     Also  of  other  shades,  and  then  having  other  names.     Often  mammillary,  botryoi- 
dal,  stalactitic,  and  occurring  lining  or  filling  cavities  in  rocks.     It  is  true  quartz,  with  some 
disseminated  opal. 

2.  Cornelian.     A  clear  red  chalcedony,  pale  to  deep  in  shade ;  also  brownish-red  to  brown, 
the  latter  kind  reddish-brown  by  transmitted  light. 

3.  Chrysoprase.      An  apple-green  chalcedony,  the  color  due  to  the  presence  of  nickel 
oxide. 

4.  Prase.     Translucent  and  dull  leek-green  ;  so  named  from  trpaaov,  a  leek.     Always  regarded 
as  a  stone  of  little  value.     The  name  is  also  given  to  crystalline  quartz  of  the  same  color. 

5.  Plasma.     Rather  bright-green  to  leek -green,  and  also  sometimes  nearly  emerald -green, 
and  subtranslucent  or  feebly  translucent ;   sometimes  dotted   with  white.      Heliotrope,  or 
Blood-stone,  is  the  same  stone  essentially,  with  small  spots  of  red  jasper,  looking  like  drops  of 
blood. 

6.  Agate.     A  variegated  chalcedony.     The  colors  are  either  banded  or  in  clouds,  or  due  to 
visible  impurities,     a.  Banded.     The  bands  are  delicate  parallel  lines,  of  white,  tendon-like, 
wax-like,  pale  and  dark-brown,  and  black  colors,  and  sometimes  bluish  and  other  shades. 
They  follow  waving  or  zigzag  courses,  and  are  occasionally  concentric  circular,  as  in  the  eye- 
agate.     The  bands  are  the  edges  of  layers  of  deposition,  the  agate  having  been  formed  by  a 
deposit  of  silica  from  solutions  intermittently  supplied,  in  irregular  cavities  in  rocks,  and 


OXYGEN    COMPOUNDS — SILICA.  265 

deriving  their  concentric  waving  courses  from  the  irregularities  of  the  walls  of  the  cavity. 
Owing  also  to  the  unequal  porosity,  agates  may  be  varied  in  color  by  artificial  means,  ft.  Ir- 
regularly clouded.  The  colors  various,  as  in  banded  agate,  j.  Colors  due  to  visible  impurities, 
including  Moss-agate,  filled  with  brown  moss-like  or  dendritic  forms  distributed  through  the 
mass  ;  Dendritic,  Agate,  containing  brown  or  black  dendritic  markings.  There  is  also  Ayatized 
wood :  wood  petrified  with  clouded  agate. 

7.  Onyx.     Like  agate  in  consisting  of  layers  of  different  colors,  but  the  layers  are  in  even 
planes,  and  the  banding  therefore  straight,  and  hence  its  use  for  cameos,  the  head  being  cut 
in  one  color,  and  another  serving  for  the  background.     The  colors  of  the  best  are  perfectly 
well  defined,  and  either  white  and  black,  or  white,  brown  and  black  alternate. 

8.  Sardonyx.     Like  onyx  in  structure,  but  includes  layers  of  carnelian  (sard)  along  with 
others  of  white  or  whitish,  and  brown,  and  sometimes  black  colors. 

9.  Jasper.     Impure  opaque  colored  quartz,     (a)  Red  iron  sesquioxide  being  the  coloring 
matter,     (b)  Brownish,  or  ochre- yellow,  colored  by  hydrous  iron  sesquioxide,  and  becoming  red 
when  so  heated  as  to  drive  off  the  water,     (c)  Dark-green  and  brownish-green,     (d)  Grayish- 
blue,     (e)  Blackish  or  brownish -black.     (/)  Striped  or  riband  jasper  (Bandjaspis,  Germ.), 
having  the  colors  in  broad  stripes,     (g)  Egyptian  jasper,  in  nodules  which  are  zoned  in  brown 
and  yellowish  colors.     Porcelain  jasper  is  nothing  but  baked  clay,  and  differs  from  true  jasper 
in  being  B.B.  fusible  on  the  edges.     Red  porphyry,  or  its  base,  resembles  jasper,  but  is  also 
fusible  on  the  edges,  being  usually  an  impure  feldspar. 

10.  Agate-Jasper.    An  agate  consisting  of  jasper  with  veinings  and  cloudings  of  chalcedony. 

11.  Siliceous  sinter.     Irregularly  cellular  quartz,  formed  by  deposition  from  waters  contain- 
ing silica  or  soluble  silicates  in  solution. 

12.  Flint  (Feuerstein,  Germ. ).     Somewhat  allied  to  chalcedony,  but  more  opaque,  and  of 
dull  colors,  usually  gray,  smoky-brown,  and  brownish-black.     The  exterior  is  often  whitish, 
from  mixture  with  lime  or  chalk,  in  which  it  is  imbedded.     Lustre  barely  glistening,  sub- 
vitreous.     Breaks  with  a  deeply  conchoidal  fracture,  and  a  sharp  cutting  edge.     The  flint  of 
the  chalk  formation  consists  largely  of  the  remains  of  infusoria  (Diatoms),  sponges,  and  other 
marine   productions.       The  coloring  matter  of   the  common  kinds  is  mostly  carbonaceous' 
matter. 

13.  Hornstone  (Hornstein,  Germ.).     Resembles  flint,  but  more  brittle,  the  fracture  more 
splintery.      Chert  is  a  term  often  applied  to  hornstone,  and  to  any  impure  flinty  rock,  includ- 
ing the  jaspers. 

14.  Basanite,  Lydian  Stone  or  Touchstone.     A  velvet-black  siliceous  stone  or  flinty  jasper, 
used  on  account  of  its  hardness  an  1  black  color  for  trying  the  purity  of  the  precious  metals. 
The  color  left  on  the  stone  after  rubbing  the  metal  across  it  indicates  to  the  experienced  eye 
the  amount  of  alloy.     It  is  not  splintery  like  hornstone. 

Pyr.,  etc. — B.B.  unaltered;  with  borax  dissolves  slowly  to  a  clear  glass;  with  soda  dis- 
solves with  effervescence  ;  unacted  upon  by  salt  of  phosphorus.  Insoluble  in  hydrochloric 
acid,  and  only  slightly  acted  upon  by  solutions  of  fixed  caustic  alkalies.  When  fused  and 
cooled  it  becomes  opal-silica,  having  G.  =2'2. 

Diff. — Quartz  is  distinguished  by  its  hardness— scratching  glass  with  facility ;  infusibility 
— not  fusing  before  the  blowpipe  ;  insolubility — not  attacked  by  water  or  the  acids  ;  undeava- 
bility — one  variety  being  tabular,  but  proper  cleavage  never  being  distinctly  observed.  To 
these  characteristics  the  action  of  soda  B.  B.  may  be  added. 

Obs. — Quartz  occurs  as  one  of  the  essential  constituents  of  granite,  syenite,  gneiss,  mica 
schist,  and  many  related  rocks  ;  as  the  principal  constituent  of  quartz-rock  and  many  sand- 
stones ;  as  an  unessential  ingredient  in  some  trachyte,  porphyry,  etc.  ;  as  the  vein-stone  in 
various  rocks,  and  for  a  large  part  of  mineral  veins ;  as  a  foreign*  mineral  in  the  cavities  of  trap, 
basalt,  and  related  rocks,  some  limestones,  etc. ,  making  geodes  of  crystals,  or  of  chalcedony, 
agate,  carnelian,  etc. ;  as  imbedded  nodules  or  masses  in  various  limestones,  constituting  the 
flint  of  the  chalk  formation,  the  hornstone  of  other  limestones — these  nodules  sometimes 
becoming  continuous  layers  ;  as  masses  of  jasper  occasionally  in  limestone.  It  is  the  principal 
material  of  the  pebbles  of  gravel  beds,  and  of  the  sands  of  the  sea- shore  and  sand  beds  every- 
where. Silica  also  occurs  in  solution  (but  mostly  as  a  soluble  alkaline  silicate)  in  heated 
natural  waters,  as  those  of  the  Geysers  of  Iceland,  New  Zealand,  and  California,  and  the 
Yellowstone  Park,  and  very  sparingly  in  many  cold  mineral  waters. 

Switzerland,  Dauphiny,  Piedmont,  the  Carrara  quarries,  and  numerous  other  foreign  locali- 
ties, afford  fine  specimens  of  rock  crystal.  Amethysts  are  brought  from  India,  Ceylon,  and 
Persia,  also  Transylvania.  The  amygdaloids  of  Iceland  and  the  Faroe  Islands,  afford  magni- 
ficent specimens  of  chalcedony ;  also  Hiittenberg  and  Loben  in  Carinthia,  etc.  The  finest 
carnelia/is  and  agates  are  found  in  Arabia,  India,  Brazil,  Surinam,  Oberstein,  and  Saxony. 
Cat's  eye,  in  Ceylon,  the  coast  of  Malabar,  and  also  in  the  Harz  and  Bavaria.  Heliotrope,  in 
Bucharia,  Tartary,  Siberia. 


266  DESCRIPTIVE   MINERALOGY. 

In  New  York,  quartz  crystals  are  abundant  in  Herkimer  Co.  Fine  dodecahedral  crystals, 
at  the  beds  of  specular  iron  in  St.  Lawrence  Co.  In  Antwerp,  Jefferson  Co. ,  at  Diamond 
Island  and  Diamond  Point,  Lake  George,  Pelham  and  Chesterfield,  Mass. ,  Paris  and  Perry, 
Me.,  Benton,  N.  H.,  Sharon,  Vt.,  Meadow  Mount,  Md.,  and  Hot  Springs,  Ark.,  are  other 
localities  of  quartz  crystal.  For  other  localities,  see  the  catalogue  of  localities  in  the  latter 
part  of  this  volume. 

Rose  quartz,  at  Albany  and  Paris,  Me. ,  Acworth,  N".  H. ,  and  elsewhere  ;  smoky  quartz,  at 
Goshen,  Mass.,  Richmond  Co.,  N.  Y.,  Pike's  Peak,  Colorado,  etc.  ;  amethyst,  at  Keweenaw 
Point  and  Thunder  Bay,  etc.,  Lake  Superior;  also  at  Bristol,  Rhode  Island,  near  Greensboro, 
N.  C.  ;  Specimen  Mountain,  Yellowstone  Park.  Crystallized  green  quartz,  at  Providence, 
Delaware  Co.,  Penn. ;  at  Ellenville,  N.  Y.  Chalcedony  and  agates  about  Lake  Superior,  the 
Mississippi,  and  the  streams  to  the  west,  etc.  Red  jasper  is  found  in  pebbles  on  the  banks  of 
the  Hudson  at  Troy  ;  red  and  yellow,  near  Murphy's,  Calaveras  Co. ,  Cal.  Heliotrope  occupies 
veins  in  slate  at  Bloomingrove,  Orange  Co.,  N.  Y. 

Several  varieties  of  this  species  have  long  been  employed  in  jewelry.  The  amethyst  has 
always  been  esteemed  for  its  beauty.  Cameos  are  in  general  made  of  onyx,  which  is  well 
fitted  for  this  kind  of  miniature  sculpture.  Jasper  admits  of  a  brilliant  polish,  and  is  often 
formed  into  vases,  boxes,  knife-handles,  etc.  It  is  also  extensively  used  in  the  manufacture 
of  Florentine  mosaics.  The  carnelian  is  often  rich  in  color,  but  is  too  common  to  be  much 
esteemed  ;  when  first  obtained  from  the  rock  they  are  usually  gray  or  grayish-red  ;  they 
receive  their  fine  colors  from  an  exposure  of  several  weeks  to  the  sun's  rays,  and  a  subsequent 
heating  in  earthen  pots.  The  colors  of  agate,  when  indistinct,  may  be  brought  out  by  boil- 
ing in  oil,  and  afterward  in  sulphuric  acid ;  the  latter  carbonizes  the  oil  absorbed  by  the 
porous  layers,  and  thus  increases  the  contrast  of  the  different  colors. 


TRIDYMITE. 

Hexagonal.     1  A  1  =  124°   3'   (basal)  ;  1  A  1  =  127°   35'  (terminal) ;  c  = 
1-6304  (v.  Rath).     Cleavage  0,  imperfect.     Crys- 
507     ^  tals   minute,  commonly  tabular  (f.  507),  formed 

by  the  prism  and  basal  plane  ;  also  frequently  in 
twins  and  trillings  with  (1)  1,  and  (2)  f  as  the 
twinning-planes.  Double  refraction  positive. 

H.=:7.  G.=r2-282-2-326.  Lustre  vitreous,  on 
the  face  pearly.  Colorless,  becoming  white  on  weathering.  Fracture  con- 
choidal. 

Comp. — Pure  silica,  or  SiO2,  like  quartz. 

Pyr. — B.B.  infusible.  Fuses  in  soda  with  effervescence,  forming  a  colorless  glass.  Soluble 
in  a  boiling  saturated  solution  of  sodium  carbonate. 

Obs. — First  found  in  cavities  in  the  trachyte  from  Cerro  St.  Cristoval,  near  Pachuca, 
Mexico.  Also  in  the  trachyte  of  the  Siebengebirge,  and  in  related  rocks  from  many  localities. 
Forming  on  one  occasion  the  mass  of  white  volcanic  ashes,  from  the  island  Vulcano.  Also 
in  microscopic  crystals  inclosed  in  opal,  and  in  quartz. 

ASMANITE  (Maskelyne). — A  third  form  of  silica,  crystallizing  in  the  orthorhombic  system, 
"isomorphous  with  brookite."  H.  =5'5.  G.  =2- £45.  Found  in  very  minute  crystalline 
grains,  generally  rounded,  in  the  meteoric  iron  of  Breitenbach. 


OPAL. 

Massive,  amorphous ;  sometimes  small  reniform,  stalactitic,  or  large 
tuberose.  Also  earthy. 

H.=5'5-6*5.  G.=l'9-2*3.  Lustre  vitreous,  frequently  subvitreous ; 
often  inclining  to  resinous,  and  sometimes  to  pearly.  Color  white,  yellow, 


OXYGEN    COMPOUNDS SILICA.  267 

red,  brown,  green,  gray,  generally  pale ;  dark  colors  arise  from  foreign 
admixtures ;  sometimes  a  rich  play  of  colors,  or  different  colors  by  refracted 
and  reflected  light.  Streak  white.  Transparent  to  nearly  opaque. 

Comp. — Silica,  Si02,  as  for  quartz,  the  opal  condition  being  one  of  lower  degrees  of  hard- 
ness and  specific  gravity.  Water  is  usually  present,  but  it  is  regarded  as  unessential.  It 
varies  in  amount  from  2  to  21  p.  c. ;  or,  mostly,  from  3-9  p.  c. 

Var. — 1.  Precious  Opal.  Exhibits  a  play  of  delicate  colors,  or,  as  Pliny  says,  presents  various 
refulgent  tints  in  succession,  reflecting  now  one  hue  and  now  another.  Seldom  larger  than  a 
hazel-nut.  Doubly  refracting  (biaxial),  Behrens. 

3.  Fire-opal.  Hyacinth-red  to  honey-yellow  colors,  with  fire-like  reflections  somewhat  irised 
on  turning. 

3.  Girasol.     Bluish-white,  translucent,  with  reddish  reflections  in  a  bright  light. 

4.  Common   Opal.     In  part  translucent ;  (a)  milk-white  to  greenish,  yellowish,  bluish ;   (b) 
Resin-opal  (Wachsopal,   Pechopal,    Germ.},   wax-,   honey-  to  ochre-yellow,  with  a  resinous 
lustre ;   (c]  dull  olive-green  and  mountain-green  ;  (d)  brick-red. 

5.  Cacholong.     Opaque,   bluish-white,   porcelain- white,  pale-yellowish  or  reddish;    often 
adheres  to  the  tongue,  and  contains  a  little  alumina. 

6.  Opal-agate.     Agate-like  in  structure,  but  consisting  of  opal  of  different  shades  of  color. 

7.  Jasp-opal.     Opal  containing  some  yellow  iron  sesquioxide  and  other  impurities,  and  hav- 
ing the  color  of  yellow  jasper,  with  the  lustre  of  common  opal. 

8.  Wood-opal  (Holzopal,  Germ. ).     Wood  petrified  by  opal. 

9.  Hyalite.     Clear  as  glass  and  colorless,  constituting  globular  concretions,  and  also  crusts 
with  a  globular,  renif orm,  botryoidal>  or  stalactitic  surface ;  also  passing  into  translucent, 
and  whitish. 

10.  Fiorite,  Siliceous  Sinter.     Includes  translucent  to  opaque,  grayish,  whitish,  or  brownish 
incrustations,  porous  to  firm  in  texture  ;  sometimes  fibrous -like  or  filamentous,  and,  when  so, 
pearly  in  lustre,  formed  from  the  decomposition  of  the  siliceous  minerals  of  volcanic  rocks 
about  fumaroles,  or  from  the  siliceous  waters  of  hot  springs.     It  graduates  at  times  into 
hyalite.      Geyserite  constitutes  concretionary  deposits  about  the  Iceland  and  Yellowstone 
(pealite)  geysers,  presenting  white  or  grayish,  porous,  stalactitic,  filamentous,  cauliflower- 
like  forms;  also  compact-massive,   and  scaly-massive;    H.  =5;  rarely  transparent,  usually 
opaque ;  sometimes  falling  to  powder  on  drying  in  the  air. 

1 1 .  Float-stone.     In  light  concretionary  or  tuberose  masses,  white  or  grayish,  sometimes 
cavernous,  rough  in  fracture.     So  light,  owing  to  its  spongy  texture,  as  to  float  on  water. 
The  concretions  sometimes  have  a  flint-like  nucleus. 

12.  Tripoiite.     Formed  from  the  siliceous  shells  of  Diatoms  and  other  microscopic  species, 
as  first  made  known  by  Ehrenberg,  and  occurring  in  deposits,  often  many  miles  in  area,  either 
uncompacted,  or  moderately  hard.     Infusoiial  Earth,  or  Earthy  Tripolite,  a  very  fine-grained 
earth  looking  often  like  an  eartny  chalk,  or  a  clay,  but  harsh  to  the  feel,  and  scratching  glass 
when  rubbed  on  it. 

Pyr.,  etc. — Yields  water.  B.B.  infusible,  but  becomes  opaque.  Some  yellow  varieties, 
containing  iron,  turn  red. 

Obs. — Occurs  filling  cavities  and  fissures  or  seams  in  igneous  rocks,  porphyry,  and  some 
metallic  veins.  Also  imbedded,  like  flint,  in  limestone,  and  sometimes,  like  other  quartz 
concretions,  in  argillaceous  beds  ;  also  formed  from  the  siliceous  waters  of  some  hot  springs ; 
also  resulting  from  the  mere  accumulation,  or  accumulation  and  partial  solution  and  solidifi- 
cation, of  the  siliceous  shells  of  infusoria — which  consist  essentially  of  opal-silica. 

Precious  opal  occurs  in  Hungary ;  in  Honduras  ;  and  Mexico.  Fire  opal  occurs  at  Zimapaii 
in  Mexico  ;  Faroe  ;  near  San  Antonio,  Honduras.  Common  opal  is  abundant  at  Telkebanya 
in  Hungary ;  in  Moravia ;  in  Bohemia  ;  Stenzelberg  in  the  Siebengebirge ;  Faroe,  Iceland ; 
the  Giant's  Causeway,  at  many  localities.  In  U.  S.,  hyalite  occurs  sparingly  in  N.  York,  at 
the  Phillips  ore  bed,  Putnam  Co. ;  in  Georgia,  in  Burke  and  Scriven  Cos.;  in  Washington  Co., 
good  fire  opal.  At  the  Geysers  on  the  Fire  Hole  river,  Yellowstone  Park,  geyserite  is  abundant. 

The  precious  opal,  when  large,  and  exhibiting  its  peculiar  play  of  colors  in  perfection,  is  a 
gem  of  high  value.  It  is  cut  with  a  convex  surface. 

MELANOPHLOGITE  (Lasaux). — Occurs  in  minute,  colorless,  cubes  coating  sulphur  crystals 
from  Girgenti,  Sicily.  Contains  SiO2  86 '3  p.  c.,  S03  7 '2,  HaO  2 '9  ;  chemical  nature  doubt- 
ful. Turns  black  upon  ignition,  hence  the  name. 


268 


DESCRIPTIVE   MINERALOGY. 


II.   TEENAKY  OXYGEN  COMPOUNDS. 


1.  SILICATES.— A.  ANHYDROUS  SILICATES. 


a.  BISILICATES. 


GENERAL  FORMULA  RSiO8. 


(a)  Amphibole  Group.     Pyroxene  Section. 
ENSTATITE.     BRONZITE.     Protobastite. 


Orthorhombic. 


508 


7A/=r88°  16'  and  91°  4A'  (Breitenbach  meteorite,  v. 
Lang)-,  c  :  I  :  a  —  0-58853  :  1-03086  :  1.  Cleavage:  7, 
easy  ;  i-i,  i-i,  less  so.  Sometimes  a  fibrous  appearance 
on  the  cleavage-surface.  Also  massive  and  lamellar. 

H.  =  5-5.  G.  =  3-1-3-3.  Lustre  a  little  pearly  on 
cleavage-surfaces  to  vitreous  ;  often  metalloidal  in  the 
bronzite  variety.  Color  grayish-white,  yellowish-white, 
greenish- white,  to  olive-green  and  brown.  Streak  un- 
colored,  grayish.  Double  refraction  positive ;  optic- 
axial  plane  brachydiagonal ;  axes  very  divergent. 


Bamle,  Norway. 
Var.  1.    With  little  or 


Comp.,  Var. 

SiO3. 


-MgSi03  =  Silica  60,  magnesia  40=  100 ;  also  (Mg, Fe) 


Enstatite.     Color  white,  yellowish,  grayish,  or  greenish- 


white ;  lustre  pearly-vitreous;  G.  =3 "10-3 '13.  Chladhite,  which  makes  up  90  p.  c.  of  the 
Bishopville  meteorite,  belongs  here  and  is  the  purest  kind  ;  Victorite  (Meunier),  from  the 
Deesa  (Chili)  meteoric  iron  is  probably  identical. 

2.  Ferriferous  ;  Bronzite.  Color  grayish-green  to  olive-green  and  brown ;  lustre  of  cleav- 
age-surface adamantine  pearly  to  submetallic  or  bronze-like.  The  ratio  of  Mg  :  Fe  varies 
from  11  :  1  to  3  :  1.  Analysis  of  bronzite  from  Leiperville  by  Pisani,  Si02  57 '08,  A1O3  0'28, 
FeO  5-77,  MgO  35 '59,  H2O  0-90=99-62. 

Pyr.,  etc. — B.B.  almost  infusible,  being  only  slightly  rounded  on  the  thin  edges ;  F.=6. 
Insoluble  in  hydrochloric  acid. 

Diff. — Distinguished  by  its  infusibility  from  varieties  of  amphibole,  which  it  resembles. 

Obs — Occurs  near  Aloysthal  in  Moravia ;  in  the  Vosges ;  at  Kupf  erberg  in  Bavaria  ;  at 
Baste  in  the  Harz  (Protobastite);  in  the  chrysolite  bombs  in  the  Eif el ;  in  immense  crystals 
with  apatite,  near  Bamle,  Norway.  In  Pennsylvania,  at  Leiperville  and  Texas  ;  at  Brewster, 
N.  Y.  Bronzite  is  quite  common  in  meteorites. 

DesCloizeaux  first  defined  the  limits  of  this  species,  as  here  laid  down. 

Named  from  'ei/o-rciTTjs,  an  opponent,  because  so  refractory.  The  name  brojizite  has  priority, 
but  a  bronze  lustre  is  not  essential,  and  is  far  from  universal. 


HYPERSTHENE. 

Orthorhombic.  /A  1=  91°  32J-,  DesCloizeaux  (Mt.  Dore) ;  9r  40', 
v.  Rath  (amblystegite).  Cleavage  :  i-l  perfect,  7  and  i-l  distinct  but  inter- 
rupted. Usually  foliated  massive. 

H.  =  5-6.  Gr.  —  3-392.  Lustre  somewhat  pearly  on  a  cleavage-surface, 
and  sometimes  a  little  metalloidal ;  often  with  a  peculiar  iridescence  due 


OXYGEN   COMPOUNDS ANIIYDKOUS    SILICATES. 


269 


to  the  presence  of  minnte  enclosed  tabular  crystals  (brookite?)  in  parallel 
position  (Kosmann).     Color  dark  brownish -green,  gray- 
ish-black,   greenish- black,    pinchbeck-brown.      Streak  509 
grayish,  brownish-gray.     Translucent  to  nearly  opaque. 
Brittle.     Optic-axial  plane  brachydiagonal ;  axes  very 
divergent ;  bisectrix  negative. 


if 


Mt.  Dore. 


Comp.— (Mg,Fe;SiO3  with  Fe  :  Mg— 1  :  5,  1:3,  etc.  If  Fe  to 
Mg  =  l  :  2  the  formula  requires  SiO,  f)4'2,  FeO  21-7,  MgO  24-1=100. 

Pyr.,  etc. — B.B.  fuses  to  a  black  enamel,  and  on  charcoal  yields  a 
magnetic  mass.  Partially  decomposed  by  hydrochloric  acid. 

Obs. — Hypersthene  occurs  at  Isle  St.  Paul,  Labrador  in  Canada ; 
at  the  Isle  of  Skye  ;  in  Greenland  ;  Norway ;  Eonsberg  in  Bohemia  ; 
the  Tyrol;  Elfdalen  in  Sweden;  Laacher  See  (amblystegite] ;  Voigt- 
land  ;  in  trachyte  of  Mt.  Dore,  Auvergne. 

In  chemical  composition,  enstatite  (and  bronzite\  and  hypersthene 
belong  together,  since  they  grade  insensibly  into  each  other;  and  in 
crystalline  form  they  are  identical.     The  essential  difference  between 
them,  according  to  DesCloizeaux,  lies  in  the  axial  dispersion  which  is  uniformly  p  <  v  f  or 
enstatite,  and  p  >  v  for  hypersthene. 

DIACLASITE. — Near  bronzite  ;  differs  in  optical  characters.  (Mg,Fe,Ca)Si03.  Harzburg; 
Gruadarrama,  Spain. 

WOLIiASTONlTE.    Tabular  Spar.     Tafelspath,  Germ. 

Monoclinic.  C=  69°  48',  /A  7  =  87°  28',  O  A  2-i  =  137°  48' ;  c  :  I  :  d 
=  0-4338  :  0-89789  :  1.  Fig.  510  in  the  pyroxene  or  normal  position,  but 
with  the  edge  O  /i-i  the  obtuse  edge  ;  f.  511  in  the  position  given  the  crys- 
tals by  authors  who  make  i-i  the  plane  O,  and  2-i  the  plane  /.  O  A  —  1-i 
=  160°  30',  O  A  1-i  =  154°  25',  i-i  A  -  2  =  132°  54',  i-i  A  2  =  93°  52'. 
Rarely  in  distinct  tabular  crystals.  Cleavage :  O  most  distinct ;  i-i  less 
so ;  1-i  and  —  1-i  in  traces.  Twins :  twinning-plane  i-i.  Usually  cleav- 
able  massive,  with  the  surface  appearing  long  fibrous,  fibres  parallel  or 
reticulated,  rather  strongly  coherent. 


510 


511 


Lustre   vitreous, 


inclining 


to  pearly  upon 


H.=4-5-5.     G.=2-78-2 

the  faces  of  perfect  cleavage.  Color  white,  inclining  to  gray,  yellow,  red, 
or  brown.  Streak  white.  Subtransparent — translucent.  Fracture  uneven, 
sometimes  very  tough.  Optic-axial  plane  i-l ;  divergence  70°  40'  for  the 
red  ravs  ;  bisectrix  of  the  acute  angle  negative ;  inclined  to  a  normal  to  i-i 
57°  48',  and  to  a  normal  to  0  12°/DesCl. 


270 


DESCRIPTIVE   MINERALOGY. 


Comp.— CaSi03— Silica  51 '7,  lime  48 '3=100. 

Pyr.,  etc. — In  the  matrass  no  change.  B.B.  fuses  easily  on  the  edges;  with  some  soda,  a 
blebby  glass,  with  more,  swells  up  and  is  infusible.  With  hydrochloric  acid  gelatinizes ;  most 
varieties  effervesce  slightly  from  the  presence  of  calcite. 

Diff. — Differs  from  asbestus,  and  tremolite  in  forming  a  jelly  with  acids,  as  also  by  its  more 
vitreous  fracture  ;  fuses  less  readily  than  natrolite  and  scolecite ;  when  pure  does  not  effer- 
vesce with  acids  like  the  carbonates. 

Obs. — Wollastonite  is  found  in  regions  of  granite  and  granular  limestone ;  also  in  basalt  and 
lavas.  Occurs  in  Hungary ;  in  Finland ;  and  in  Norway ;  at  Gockum  in  Sweden ;  in  the 
Harz  ;  at  Auerbach,  in  granular  limestone  ;  at  Vesuvius.  In  the  U.  S. ,  in  N.  York,  at  Wills- 
borough  ;  at  Lewis  ;  Diana,  Lewis  Co.  In  Penn.,  Bucks  Co.  At  the  Cliff  Mine,  Keweenaw 
Point,  Lake  Superior.  In  Canada,  at  Grenville. 


PYROXENE. 


Monoclinic.  <7=73°59/,  /A  7=87°  5',  0  A  2-1  =  131°  17';  c  :  I  :  d 
=  0-5412  :  0-91346  :  1.  O  A  7=  100°  57',  O  A  —  \-i  =  155°  51',  O  A  \4 
=  148°  35',  O  A  -1  =  146°  9',  0Al  =  137°  49',  -1 A -1  =  131°  24'. 
Cleavage :  I  rather  perfect,  often  interrupted ;  i-i  sometimes  nearly  per 


515 


516 


519 


feet ;  i-\  imperfect ;  0  sometimes  easy.  Crystals  usually  thick  and  stout 
Twins :  t  winning-plane  i-i  (f.  521).  Often  coarse  lamellar,  in  large  masses, 
parallel  to  O  or  i-i.  Also  granular,  particles  coarse  or  line ;  and  fibrous, 
fibres  often  fine  and  long. 

H.=:5-6.  G.=3-23-3-5.  Lustre 
vitreous,  inclining  to  resinous ; 
some  pearly.  Color  green  of 
various  shades,  verging  on  one 
side  to  white  or  grayish-white, 
and  on  the  other  to  brown  and 
black.  Streak  white  to  gray  and 
grayish-green.  Transparent  — 
opaque.  Fracture  conchoidal — 
uneven.  Brittle.  In  crystals 
from  Fassa,  optic-axial  plane  i-\\ 
divergence  110°  to  113°  ;  bisec- 
trix of  the  acute  angle  positive, 
inclined  51°  6'  to  a  normal  to  i-i  and  22°  55'  to  a  normal  to  O,  DesCl. 


OXYGEN    COMPOUNDS — ANHYDROUS    SILICATES.  271 

Comp.,  Var. — A  bisilicate,  having  the  general  formula  RSJ03,  where  R  may  be  Ca,Mg, 
Fe,Mn,  sometimes  also  Zn,Ka2,Na2.  Usually  two  or  more  of  these  bases  are  present.  The 
first  three  are  most  common ;  but  calcium  is  the  only  one  that  is  present  always  and  in  large 
percentage.  Besides  the  substitutions  of  the  above  bases  for  one  another,  these  same  bases 
are  at  times  replaced  by  Al,Fe,Mn,  though  sparingly,  and  the  silicon  occasionally  by  alumi- 
num. 

The  varieties  proceeding  from  these  isomorphous  substitutions  are  many  and  diverse  ;  and 
there  are  still  others  depending  on  the  state  of  crystallization.  The  foliated  and  fibrous 
kinds  early  received  separate  names,  and  for  a  while  were  regarded  as  distinct  species.  Fibrous 
or  columnar  forms  are  very  much  less  common  than  in  hornblende,  and  lamellar  or  foliated 
kinds  more  common.  The  crystals  are  rarely  long  and  slender,  or  bladed,  like  those  of  that 
species. 

The  most  prominent  division  of  the  species  is  into  (A)  the  non-aluminous  ;  (B)  the  alumi- 
nous. But  the  former  of  these  groups  shades  imperceptibly  into  the  latter.  These  two  groups 
are  generally  subdivided  according  to  the  prevalence  of  the  different  protoxide  elements. 
Yet  here,  also,  the  gradation  from  one  series  to  another  is  in  general  by  almost  insensible 
shades  as  to  composition  and  chemical  characters,  as  well  as  all  physical  qualities. 

I.  CONTAINING  LITTLE  OR  NO  ALUMINA. 

1.  Lime-Magnesia  Pyroxene;  MALACOLITE.    Diopside,  Alalite,  White  Coccolite.     Color 
white,  yellowish,  grayish-white  to  pale  green.     In  crystals  :  cleavable  and  granular  massive. 
Sometimes  transparent  and  colorless.    Gr.  =8  '2-3  '88.    Formula,  CaMgSi2O6  —  Silica  55  '6,  mag- 
nesia 18 '5,  lime  25-9.     Sometimes  Ca  :  Mg=l  :  2  ;  less  than  4  p.  c.  of  iron  are  present. 

2.  Lime- Magnesia- Iron  Pyroxene  ;  SAHLITE..     Color  grayish-green  to  deep  green  and  black ; 
sometimes  grayish  and  yellowish-white.      In  crystals  ;  also  cleavable  and  granular  massive. 
G.  =3  "25-8-4.     Named  from  Sala  in  Sweden,  one  of  its  localities,  where  the  mineral  occurs 
in  masses  of  a  grayish-green  color,  having  a  perfect  cleavage  parallel  to  the  basal  plane  ( 0). 
Formula  (Ca,Mg,Fe)SiO3.  Theratioof  Ca  :  Mg  :  Fe  varies  much,  =8  :  3  :  1,  2  :  2  :  l,etc.   The 
ratio=4  :  3  :  1,  corresponds  to  silica  53 '7,  magnesia  13 '4,  lime  24*9,  iron  protoxide  8  "0=100. 

DIALLAGE.  Part  of  the  so-called  diallage,  or  thin- foliated  pyroxene,  belongs  here,  and  the 
rest  under  the  corresponding  division  of  the  aluminous  pyroxenes.  Color  grayish-green  to 
bright  grass-green,  and  deep  green;  lustre  of  cleavage  surface  pearly,  sometimes  metal! oidal 
or  brassy.  H.=4.  G-.  =3 '2-3 "85.  Composition  near  the  preceding  ;  analysis  by  vom  Rath, 
Neurode,  Si02  53  "60,  A1O3  1  "99,  FeO  8 "95,  MnO  0-28,  MgO  13"08,  CaO  21-06,  H,O  0-86=99-83. 
With  this  variety  belongs  part  also  of  what  has  been  called  hypersthene  and  bronzite — the  part 
that  is  easily  fusible.  Common  especially  in  serpentine  rocks.  Named  from  (ka/i/iay//,  dif- 
ference, in  allusion  to  the  dissimilar  cleavages. 

3.  Iron- Lime  Pyroxene.     HEDENBEK.GITE.      Color  black.      In  crystals,  and  also  lamellar 
massive  ;  cleavage  easy  parallel  to  i-i.    G.  =3 '5-3 -58.    Formula  CaFeSiaO6  (Mg  being  absent) 
—  Silica  4839,  lime  22  "18,  iron  protoxide  29-43=100.     Asteroite  is  a  similar  pyroxene  con- 
taining also  Mn  (Igelstrom),  Sweden. 

4.  Lime-Iron-Manganese- Zinc  Pyroxene  ;  JEPFERSONITE.    Color  greenish-black.    Crystals 
often  very  large  (3-4  in.  thick),  with  the  angles  generally  rounded,  and  the  faces  uneven,  as 
if   corroded.      G.=3'36.      Analysis,  Franklin,  N.  J.,  by  Pisani,  SiO,  45  -95,  A1O3  0-85,  FeO 
8-91,  MnO  10"20,  ZnO  1015,  CaO  21-55.  MgO  3-61,  ign  0-35=101 -57. 

II.  ALUMINOUS. 

Aluminous  Lime-Magnesia  Pyroxene;  LEUCAUGITE  (Dana).  Color  white  or  grayish. 
Analysis,  Bathurst,  C.,  by  Hunt,  SiO-j  51 '50,  A1O3  6-15,  FeO3  0"35,  MgO  17 "69,  CaO  23 "80, 
H2O  1  -10=100-59.  Looks  like diopside.  H.=6'5.  G.=3'19.  Hunt.  Named  from  Aewcoc, 
white. 

Aluminous  Lime- Magnesia- Iron  Pyroxene  ;  FASSAITE,  AUGITE.  Color  clear  deep-green  to 
greenish-black  and  black ;  in  crystals,  and  also  massive  ;  subtranslucent  to  opaque.  G. 
=3'25-3'5.  Contains  iron,  with  calcium  and  magnesium,  also  aluminum.  Analysis  of  augite 
from  Montreal  by  Hunt,  Si02  49-40,  A1O3  6'70,  ifeO3  7 '83.  MgO  13-06,  CaO  21-88.  Na2O  0'74, 
H.,O  0-50=100'  11. 

a.  Fassaitd  (or  Pi/rgom).     Includes  the  green  kinds  found  in  metamorphic  rocks.     Named 
from  the  locality  at  Fassa  in  Piedmont,  which  affords  deep-green  crystals,  sometimes  pistachio- 
green,  like  the  epidote  of  the  locality. 

b.  Augite.     Includes  the  greenish  or  brownish-black  and  black  kinds,  occurring  mostly  in 
eruptive  rocks,  but  also  in  fuetamorphic.     Named  from  dt^,  lustre. 


272 


DESCRIPTIVE   MINERALOGY. 


Pyr.,  etc. — Varying  widely,  owing  to  the  wide  variations  in  composition  in  the  different 
varieties,  and  often  by  insensible  gradations.  Fusibility,  from  the  almost  infusible  diallage 
to  3 '75  in  diopside  ;  3 "5  in  sahlite  ;  3  in  jeffersonite  and  augite  ;  25  in  hedenbergite.  Va- 
rieties rich  in  iron  afford  a  magnetic  globule  when  fused  on  charcoal,  and  in  general  their 
fusibility  varies  with  the  amount  of  iron.  Jeffersonite  gives  with  soda  on  charcoal  a  reaction 
for  zinc  and  manganese ;  many  others  also  give  with  the  fluxes  reactions  for  manganese.  Most 
varieties  are  unacted  upon  by  acids. 

Diff.— See  Amphibole,  p.  275. 

Obs. — Pyroxene  is  a  common  mineral  in  crystalline  limestone  and  dolomite,  in  serpentine, 
and  in  volcanic  rocks  ;  and  occurs  also,  but  less  abundantly,  in  connection  with  granitic  rocks 
and  metamorphic  schists.  The  pyroxene  of  limestone  is  mostly  the  white  and  light-green  or 
gray  varieties ;  that  of  most  other  metamorphic  rock,  sometimes  white  or  colorless,  but 
usually  green  of  different  shades,  from  pale  green  to  greenish-black,  and  occasionally  black ; 
that  of  serpentine  is  sometimes  in  fine  crystals,  but  often  of  the  foliated  green  kind  called 
diallage  ;  that  of  eruptive  rocks  is  the  black  to  greenish-black  augite. 

Prominent  foreign  localities  are  :  malacolite  (diopside},  Traversella,  Ala  in  Piedmont ;  Sala, 
Tunaberg.  Sweden  ;  Pargas  ;  Achmatovsk;  etc.  Sahlite,  Sala;  Arendal;  Degeroe  ;  Schwarzen- 
berg ;  etc.  Hedenbergite,  Tunaberg;  Arendal.  Augite,  Fassathal ;  Vesuvius;  etc. — inmost 
dolerytic  igneous  rocks. 

In  N.  America  common  (see  list  of  localities  at  the  close  of  the  volume).  Some  localities 
are:  In  Mass.,  at  the  Bolton  quarries.  In  Conn.,  at  Canaan.  In  N.  York,  at  Warwick,  Mon- 
roe, Edenville,  Diana.  In  N.  Jersey,  in  Franklin.  In  Penn.,  near  Attleboro'.  In  Canada, 
at  Bytown,  at  Calumet  I. ,  at  Grenville. 

ACMITE. — Monoclinic.  In  slender  pointed  crystals  (hence  name)  in  quartz.  H.  =6.  Gr.  = 
3 '2-3 '53.  Color  brownish  to  reddish-brown,  in  the  fracture  blackish-green.  Opaque.  Frac- 
ture uneven.  Brittle.  RSi03,R=Na2,Fe,  or  Fe(Fe=3R);  analysis  by  Rammelsberg.  SiOa 
51-66,  FeO3  28'28,  FeO  5'23,  MnO  0-69,  Na20  12'46,  K20  0'43,  TiO  I'll,  ign  0'39=100-25. 
Kongsberg,  Norway. 

^BGIRITE. — Near  pyroxene  in  form,  but  contains  alkalies.  H.=5'5-6.  £.=3 '45-3 -58. 
Color  greenish-black.  Subtranslucent  to  opaque.  Analysis  Ramm.,  Brevig,  SiO?  50 '25,  A103 
1-22,  FeC-3  22-07,  FeO  8-80,  MnO  1-40,  CaO  5 '47.  MgO  1'28,  Na.O  9  29,  K20  0'94=100'72. 
Also  from  Magnet  Cove,  Arkansas. 


RHODONITE. 


Triclinic,  but  approximately  isomorphous  with  pyroxene.     Cleavage  : 
perfect  ;   0  less  perfect.     Usually  massive. 


522 


H.=5-5-6-5.  G.  =  3-4-3-68.  Lustre  vitreous.  Color 
light  brownish-red,  flesh-red,  sometimes  greenish  or 
yellowish,  when  impure  ;  often  black  outside  from  ex- 
posure. Streak  white.  Transparent  —  opaque.  Frac- 
ture conchoidal  —  uneven.  Very  tough  when  massive. 

Comp.,  Var.  —  MnSi03  =  Silica  45  '9,  manganese  protoxide  541=: 
100.  Usually  some  Fe  and  Ca,  and  occasionally  Zn  replace  part  of  the 
Mn.  Ordinary,  (a)  Crystallized.  Either  in  crystals  or  foliated. 
The  ore  in  crystals  from  Paisberg,  Sweden,  was  named  Paisbergite 
under  the  idea  that  it  was  a  distinct  species.  (b)  Granular  massive. 
Calciferol;  BUSTAMITE.  Contains  9  to  15  p.  c.  of  lime  replacing 
part  of  the  manganese.  Often  also  impure  from  the  presence  of  cal- 

cium carbonate,  which  suggests  that  part  of  the  lime  replacing  the  manganese  may  have  come 
from  partial  alteration.  Grayish-red.  Zinciferous  ;  FOWLERITE.  In  crystals  and  foliated, 
the  latter  looking  much  like  cleavable  red  feldspar  ;  the  crystals  sometimes  half  an  inch  to  an 
inch  through.  JA  7=86°  30',  Torrey.  G.=3'44,  Thomson. 

Pyr.,  etc.  —  B.B.  blackens  and  fuses  with  slight  intumescence  at  2'5  ;  with  the  fluxes  gives 
reactions  for  manganese  ;  fowlerite  gives  with  soda  on  charcoal  a  reaction  for  zinc.  Slightly 
acted  upon  by  acids.  The  calciferous  varieties  often  effervesce  from  mechanical  admix- 
ture with  calcium  carbonate.  In  powder,  partly  dissolves  in  hydrochloric  acid,  and  the  in- 
Boluble  part  becomes  of  a  white  color.  Darkens  on  exposure  to  the  air,  and  sometimes 
becomes  nearly  black. 

Obs.—  Occurs  at  Longban,  near  Philipstadt  in  Sweden  ;  also  in*the  Harz  ;  in  the  district  of 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


273 


Katherinenberg  in  the  Ural ;  in  Cornwall,  etc.  Occurs  in  Warwick,  Mass.  ;  Blue  Hill  Bay, 
Maine  ;  near  Hinsdale,  N.  H.  •  fowlerite  (keatingine)  at  Hamburg  and  Sterling,  New  Jersey. 

Named  from  pdrlov,  a  rose,  in  allusion  to  the  color. 

BABINGTONITE.— Triclinic.  9RSiO3+FeSi3O9,  with  R=Fe(Mn)  :  Ca(Mg)-2  :  3  (Ramm.). 
Analysis,  Rammelsberg,  SiO2  51'22,  Fe03  ll'OO,  FeO  10'26,  MnO  7'91,  MgO  0'77,  CaO 
19*32,  ign=0'44=:l(jO-92.  Color  greenish-black.  Arendal;  Nassau;  Devonshire;  BavenO. 


SPODUMENE. 

Monoclinic.      O=  69°  40'  /A  7=  87°,    0  A  24  =  130°  30'.      Crystals 
large.     Cleavage:  i-i  very  perfect;  /  also  perfect; 
14  in  traces ;  in  striae  on  i-i.     Twins :  twinning- plane 
i-i.     Also  massive,  with  broad  cleavage  surface. 

H.  =  6-5-7.  G.  — 3-13-3-19.  Lustre  pearly.  Cross 
fracture  vitreous.  Color  grayish-green,  passing  into 
greenish-white  and  grayish- white,  rarely  faint-reddish. 
Streak  uncolored.  Translucent — subtranslucent.  Frac- 
ture uneven. 

t 

Comp.— 3RSiO3+4A-lSi309;  R=Li2  mostly.  Silica  64  "2,  alu- 
mina 29 '4,  lithia  6 -4=100.  Sometimes  Li  :  Na(K)=20  :  1,  Ramm. 

Pyr.,  etc. — B.  B.  becomes  white  and  opaque,  swells  up,  imparts 
a  purple  red  color  (lithia)  to  the  flame,  and  fuses  at  3  "5  to  a  clear 
or  white  glass.  The  powdered  mineral,  fused  with  a  mixture  of 
potassium  bisulphate  and  fluor  on  platinum  wire,  gives  a  more  in- 
tense iithia  reaction.  Not  acted  upon  by  acids. 

Diff. — Distinguished  by  its  perfect  orthodiagonal  as  well  as 
prismatic,  cleavage  ;  has  a  higher  specific  gravity  and  more  pearly 
lustre  than  feldspar  or  scapolite.  Gives  a  red  flame  B.B. 

Obs. — Occurs  on  the  island  of  Uto,  Sweden  ;  near  Sterzing  and 

Lisens  in  the  Tyrol;  at  Killiney  Bay,  near  Dublin,  and  at  Peterhead  in  Scotland.  At  Goshen, 
Mass.  ;  also  at  Chesterfield  and  Norwich,  Mass. ;  at  Windham,  Maine ;  at  Winchester,  N.  H. ; 
at  Brookfield,  Ct. 

PETALITE.— 3Li2Si2O6+4A]Si6O15=Silica  77'97,  alumina  17*79,  lithia  3'57,  soda  067= 
100.  Ramm.  Q.  ratio  Li  :  Al  :  Si=l  :  4  :  20,  or  for  bases  to  silicon=l  :  4.  H.=6-6'5.  G. 
=2  -5.  Colorless ;  white.  Uto,  Sweden ;  Elba  (castorite) ;  Bolton,  Mass. 


Norwich,  Mass. 


AmphiboU  Section. 


ANTHOPHYLLITE. 


Orthorhombic.  I\T=  125°  to  1253  25'.  Cleavage:  i-i  perfect,  /  less 
so,  i-'l  difficult.  Commonly  lamellar,  or  fibrous  massive ;  fibres  often  very 
slender. 

H.=5'5.  G.  =  3-l-3'2.  Lustre  somewhat  pearly  upon  a  cleavage  sur- 
face. Color  brownish-gray,  yellowish-brown,  brownish-green,  sometimes 
submetallic.  Streak  uncolored  or  grayish.  Translucent  to  subtranslucent. 
Brittle.  Double  refraction  positive ;  optical  axes  in  the  brachy diagonal 
section. 

18 


274 


DESCRIPTIVE   MINERALOGY. 


Comp.— (Fe,Mg)Si03,  Fe  :  Mg=l  :  3=Silica  55 '5,  magnesia  27*8.  iron  protoxide  167= 
100. 

Pyr.,  etc. — B.B.  fuses  with  great  difficulty  to  a  black  magnetic  enamel;  with  the  fluxes 
gives  reactions  for  iron  ;  unacted  upon  by  acids. 

Obs. — Occurs  near  Kongsberg  in  Norway,  and  near  M-odum.  Also  at  Hermannschlag, 
Moravia. 

Anthophyllite  "bears  the  same  relation  to  the  Amphibole  Group  that  enstatite  and  hyper- 
sthene  do  to  the  Pyroxene  Group. 

KUPFPEKITE. — Probably  MgSiO3,  with  a  little  Fe.  1 A  7=124°  30',  hence  an  enstatite-horn- 
blende.  Color  emerald-green  (chrome).  Tunkinsk  Mts. ,  Miask.  Analysis  of  a  similar  min- 
eral from  Perth,  Canada,  Thomson,  Si02  57-60,  A103  3'20,  FeO  210,  MgO  39-30,  CaO  3-55, 
ign.  3-55=99-30. 


AMPHIBOLE.    HORNBLENDE. 

Monoclinic.  O=  75°  2',  I/\  1=  124°  30',  O  A 14  =  164°  10',  c\l\a 
=0-5527  :  1*8825  :  1.  Crystals  sometimes  stout,  often  long  and  bladed. 
Cleavage :  I  highly  perfect ;  i-i,  i-l  sometimes  distinct.  Lateral  planes 
often  longitudinally  striated.  Twins :  twinning-plane  i-i,  as  in  f .  527  (simple 
form  f.  526),  and  530.  Imperfect  crystallizations :  fibrous  or  columnar, 
coarse  or  fine,  fibres  often  like  flax ;  sometimes  lamellar ;  also  granular 
massive,  coarse  or  fine,  and  usually  strongly  coherent,  but  sometimes 
friable. 


525 


528 


530 


H.  =  5-6.  G.=r2-9-3'4.  Lustre  vitreous  to  pearly  on  cleavage-faces; 
fibrous  varieties  often  silky.  Color  between  black  and  white,  through  vari- 
ous shades  of  green,  inclining  to  blackish-green.  Streak  uncolored,  or  paler 
than  color.  Sometimes  nearly  transparent ;  usually  subtranslucent — opaque. 
Fracture  subconchoidal,  uneven.  Bisectrix,  in  most  varieties,  inclined  about 
60°  to  a  normal  to  O,  and  15°  to  a  normal  to  i-i\  and  double  refraction 
negative. 

Comp.,  Var. — General  formula  RSi03,  as  for  pyroxene.  Aluminum  is  present  in  most 
amphibole,  and  when  so  it  usually  replaces  silicon.  R  may  correspond  to  two  or  more  of  the 
basic  elements  Mg,Ca,Fe,Mn,Na2,K2,H2 ;  and  ft  to  Al,  Fe  or  Mn.  Fe  sometimes  replaces 
silicon,  like  Al.  Much  amphibole,  especially  the  aluminous,  contains  some  fluorine.  The  base 
calcium  is  absent  from  some  varieties,  or  nearly  so. 

The  varieties  of  amphibole  are  as  numerous  as  those  of  pyroxene,  and  for  the  same  reasons ; 
and  they  lead  in  general  to  similar  subdivisions. 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES.  275 


I.  CONTAINING   LITTLE   on   NO   ALUMINA. 

-Lime  Amphibole ;  TREMOLITE.  Grammatite.  Colors  white  to  dark-gray.  In 
distinct  crystals,  either  long  bladed  or  short  and  stout ;  long  and  thin  columnar,  or  fibrous  ; 
also  compact  granular  massive.  7  A  7=124°  30'.  H.  =5  "0-6 '5.  G.  =2  9-3'l.  Sometimes 
transparent  and  colorless.  Contains  magnesia  and  lime  with  little  or  no  iron  ;  formula  (Ca. 
Mg)SiO3,  Ca  :  Mg=l  :  3  =  SHica  57'70,  magnesia  28  "85,  lime  13'35  =  100.  Named  Tremolite  by 
Pini,  from  the  locality  at  Tremola  in  Switzerland. 

NEPHRITE. — In  part  a  tough,  compact,  fine  grained  tremolite,  having  a  tinge  of  green  or 
blue,  and  breaking  with  a  splintery  fracture  and  glistening  lustre.  H.  =6-6 '5.  G.  =2'96-3'l. 
Named  from  a  supposed  efficacy  in  diseases  of  the  kidney,  from  veppoc,  kidney.  It  occurs 
usually  associated  with  talcose  or  magnesian  rocks.  Nephrite  or  jade  was  brought  in  the 
form  of  carved  ornaments  from  Mexico  or  Peru  soon  after  the  discovery  of  America.  A  simi- 
lar stone  comes  from  China  and  New  Zealand. 

A  nephrite-like  mineral,  called  bowsnitt,  from  Smithfield,  R.  I.,  having  the  hardness  5 '5  is 
serpentine  in  composition.  The  jade  of  de  Saussure  is  the  saussurite  (see  under  ZOISITE) 
of  the  younger  de  Saussure.  Another  aluminous  jade  has  been  called  jadeite  (q.  v.)  by 
Damour. 

Ma gnefiia-  Lime  -Iron  Amphibole;  ACTINOLITE.  Strahlstein,  Germ.  Color  bright-green 
and  grayish -green.  In  crystals,  either  short  or  long-bladed,  as  in  tremolite ;  columnar  or 
fibrous;  granular  massive.  G.  =3-32.  Sometimes  transparent.  Contains  magnesia  and 
lime,  with  some  iron  protoxide,  but  seldom  more  than  6  p.  c.  ;  formula  (Ca,Mg.Fe)Si03. 
The  variety  in  long  bright-green  crystals  is  called  glassy  actinolite  ;  the  crystals  break  easily 
across  the  prism.  The  fibrous  and  radiated  kinds  are  often  called  asbestij'orm  actinolite  and 
radiated  actinolite.  Actinolite  owes  its  green  color  to  the  iron  present. 

Iron- Magnesia  Amphibole  ;  CUMMINGTONITE.  Color  gray  to  brown.  Usually  fibrous  or 
fibre-lamellar,  often  radiated.  G.  =3 '1-3 '32.  Contains  much  iron,  with  some  magnesia,  and 
little  or  no  lime.  Formula  (Fe,Mg)Si03.  Named  from  the  locality,  Cummington,  Mass. 

ASBKSTUS.  Tremolite,  actinolite,  and  other  varieties  of  amphibole,  excepting  those  con- 
taining much  alumina,  pass  into  fibrous  varieties,  the  fibres  of  which  are  sometimes  very 
long,  fine,  flexible,  and  easily  separable  by  the  fingers,  and  look  like  flax.  These  kinds,  like 
the  corresponding  of  pyroxene,  are  called  asbestus  (fr.  the  Greek  for  incombustible').  The 
colors  vary  from  white  to  green  and  wood-brown.  The  name  amianthus  is  now  applied  usu- 
ally to  the  finer  and  more  silky  kinds.  Much  that  is  so  called  is  chryzotile,  or  fibrous  serpen- 
tine, it  containing  12  to  14  p.  c.  of  water.  Mountain  leather  is  a  kind  in  thin  flexible  sheets, 
made  of  interlaced  fibres  ;  and  mountain  cork  (Bergkork)  the  same  in  thicker  pieces ;  both 
are  so  light  as  to  float  on  water,  and  they  are  often  hydrous.  Mountain  wood  (Bergholz, 
Holzasbest,  Germ.}  is  compact  fibrous,  and  gray  to  brown  in  color,  looking  a  little  like  dry 
wood. 


II.  ALUMINOUS. 


Aluminous  Magnesia- Lime  Amphibole.  (a}  EDENITE.  Color  white  to  gray  and  pale-green, 
and  also  colorless  ;  G.  =3*0-3-059,  Ramm.  Resembles  an thophyllite  and  tremolite.  Named 
from  the  locality  at  Edenville,  N.  Y.  (for  analysis,  see  below.)  To  this  variety  belong  various 
pale-colored  amphiboles,  having  less  than  five  p.  c.  of  oxide  of  iron. 

(b)  SMAIIAGDITE  Saussure.  A  thin -foliated  variety ,  of  a  light  grass-green  color,  resembling 
much  common  green  diallage.  According  to  Boulanger  it  is  an  aluminous  magnes:a-lime 
amphibole,  containing  less  than  3£  p.  c.  iron  protoxide,  and  is  hence  related  to  edenite  and 
the  light  green  Pargas  mineral.  DesCloizeaux  observes  that  it  has  the  cleavage,  and  appar- 
ently the  optical  characters,  of  amphibole.  H.  =5;  G.=3.  It  forms,  along  with  whitish  or 
gree'nish  saussurite,  a  rock. 

Aluminous  Magnesia- Lime- Iron  Amphibole.  (a)  PARGASITE  ;  (&)  HORNBLENDE.  Colors 
bright,  dark,  green,  and  bluish-green  to  grayish-black  and  black.  /A  7=124°  l'-124:>  25' ; 
G.  =3  05-3 '47.  Pargasite  is  usually  made  to  include  green  and  bluish-green  kinds,  occurring 
in  stout  lustrous  crystals,  or  granular ;  and  hornblende  the  greenish-black  and  black  kinds, 
whether  in  stout  crystals  or  long  bladed,  columnar,  fibrous,  or  massive  granular.  But  no 
line  can  be  drawn  between  them.  Pargasite  occurs  at  Pargas,  Finland,  in  bluish-green  and 
grayish-black  crystals. 

Composition  shown  by  the  following  analyses  by  Rammelsberg ;  (1)  from  Edenville ;  (2) 
Wolfsberg,  Bohemia  ;  (3)  Brevig. 


276  DESCRIPTIVE    MINERALOGY. 


Si02 

A103 

Fe03 

FeO 

MnO      MgO 

CaO 

Na.O 

K2O 

H2O(ign) 

(1) 

51-67 

5-75 

2-86 



23-37 

,12-42 

0-75 

0-84 

0-46-9H-12 

(2) 

41-98 

14-31 

5-81 

7 

•18 



14-06 

12-55 

1-64 

1-54 

0-26=9910 

(3) 

43-28* 

6-31 

6-02 

21 

•72 

1-13 

3-62 

9-68 

3-14 

2-65 

0-48=98-63 

*  With 

I'Ol  TiO2. 

Pyr.,  etc. — The  observations  under  pyroxene  apply  also  to  this  species,  it  being  impossible 
to  distinguish  the  varieties  by  blowpipe  characters  alone. 

Diff — Distinguished  from  pyroxene  (and  tourmaline)  by  its  distinct  prismatic  cleavage, 
yielding  an  angle  of  124°.  Also  in  colored  varieties  by  its  dichroism,  when  examined  in  thin 
sections.  Fibrous  and  columnar  forms  are  much  more  common  than  with  pyroxene,  lamellar 
and  foliated  forms  rare.  Crystals  often  long,  slender,  or  bladed.  Differs  from  the  fibrous 
zeolites  in  not  gelatinizing  with  acids. 

Isomorphous  and  DimorpJwus  relations  to  Pyroxene. — The  analogy  in  composition  between 
pyroxene  and  hornblende  has  been  abundantly  illustrated.  They  have  the  same  general 
formula ;  and  under  this  formula  there  is  but  one  difference  of  any  importance,  viz. ,  that 
lime  is  a  prominent  ingredient  in  all  the  varieties  of  pyroxene,  while  it  is  wanting,  or  nearly 
so,  in  some  of  those  of  hornblende.  The  analogy  between  the  two  species  in  crystallization, 
or  their  essential  isomorphism,  was  pointed  out  by  G.  Hose  in  1831,  who  showed  that  the 
forms  of  both  were  referable  to  one  and  the  same  fundamental  form.  The  prism  /  of  horn- 
blende corresponds  in  angle  to  i-2  of  pyroxene.  Calculating  from  the  angle  /A  /in  pyroxene, 
87°  5',  the  angle  of  i-2  is  precisely  124  J  30',  or  the  angle  /A  /in  hornblende.  But  while  thus 
isomorphous  in  axial  relations  or  form,  they  are  also  dimorphous.  For  (1)  the  cleavage  in 
pyroxene  is  parallel  to  the  prism  of  87°  5',  and  in  hornblende  to  that  of  124£°.  (2)  The  occur- 
ring secondary  planes  of  the  latter  are  in  general  diverse  from  those  of  the  former,  so  that  the 
crystals  differ  strikingly  in  habit  or  system  of  modifications.  Moreover,  in  pyroxene  colum- 
nar and  fine  fibrous  forms  are  uncommon ;  in  hornblende,  exceedingly  common.  (3)  The 
several  chemical  compounds  under  pyroxene  have  one-tenth  higher  specific  gravity  than  the 
corresponding  ones  under  hornblende. 

Vom  Rath  has  described  the  occurrence  of  minute  crystals  of  hornblende  in  parallel  posi- 
tion upon  crystals  of  pyroxene  (Vesuvius),  and  in  consequence  of  the  relation  between  the  two 
forms,  thus  brought  out,  suggests  a  change  in  the  commonly  accepted  fundamental  form  of 
the  latter.  (Jahrb.  Min.,  1876.)  This  association  of  crystals  of  the  two  species  in  parallel 
position  is  not  uncommon. 

Obs. — Amphibole  occurs  in  many  crystalline  limestones,  and  metamorphic  granitic  and 
schistose  rocks,  and  sparingly  in  serpentine,  and  volcanic  or  igneous  rocks.  Tremolite,  the- 
magnesia-lime  variety,  is  especially  common  in  limestones,  particularly  magnesian  or  dolomi- 
tic  ;  acttnolite,  the  magnesia-lime-iron  variety,  in  steatitic  rocks ;  and  brown,  dark-green, 
and  black  hornblende,  in  chlorite  schists,  mica  schist,  gneiss,  and  in  various  other  rocks 
(syenyte,  dioryte,  etc.),  of  which  it  forms  a  constituent  part.  Asbestus  is  often  found  in  con- 
nection with  serpentine.  Hornblende  is  often  disseminated  in  black  prismatic  crystals  through 
trachyte,  and  also  through  other  igneous  rocks,  especially  the  feldspathic  kinds. 

Aussig  and  Teplitz  in  Bohemia,  Tunaberg  in  Sweden,  and  Pargas  in  Finland,  afford  fine 
specimens  of  the  dark-colored  hornblendes.  Actinolite  in  the  Zillerthal;  tremolite  at  St. 
Gothard,  in  granular  limestone  or  dolomite ;  the  Tyrol ;  the  Bannat,  etc.  Asbes.tus  is  found 
in  Savoy,  Salzburg,  the  Tyrol;  in  the  island  of  Corsica.  Some  localities  in  the  U.  S.  are  :  — 
Carlisle,  Pelham,  etc.,  Mass.,  cummin gtonite  at  Cummington.  In  Conn.,  white  crystals  of 
tremolite  in  dolomite,  Canaan.  In  N.  Tork^  Willsboro',  St.  Lawrence  Co.;  Warwick;  with 
pyroxene  at  Edenviile;  near  Amity  ;  in  Rossie  ;  the  variety  pargasite  in  large  white  crystals 
at  Diana,  Lewis  Co.  In  Penn.,  actinolite  at  Mineral  Hill,  in  Delaware  Co.;  at  Unionville. 
In  Maryland,  actinolite  and  asbestus  at  the  Bare  Hills ;  asbestus  at  Cooptown. 

HEXAGONITE. — Described  as  a  new  mineral  by  Goldsmith,  but  shown  by  Kcenig  to  be  only 
a  variety  of  tremolite.  From  Edwards,  St.  Lawrence  Co.,  N.  Y. 

ARFVEDSONITE. — Near  hornblende,  but  contains  alkalies.  Analysis,  Ramm.,  Greenland. 
SiO.2  51-22,  ^1O3  tr..  Fe03  23 "75,  FeO  7'80,  MnO  112,  CaO  2'08,  MgO  0'90,  Na2O  10'58, 
K  O  0-68,  ign  0*16  =  98 '29.  Greenland  ;  Brevig  ;  Arendal. 

CROCIDOLTTE. — Composition  uncertain,  near  arfvedsonite.  Analysis,  Stromeyer,  SiO2 
51-22,  FeO  34 -08,  MnO  (HO,  MgO  2 "48,  CaO  0'03,  Na2O  7'07,  H.O  4"80=99'78.  Fibrous, 
asbestus-like.  Sometimes  altered  to  " Faserquarz."  Color  lavender-blue  or  leek-green. 
Orange  river,  So.  Africa,  Vosges  Mts. 

GASTALDITE. — Monoclinic.  Cleavage  prismatic,  I/\l  =  124°  25'  (like  amphibole).  H.  = 
6-7.  G.=3'044.  Color  dark-blue  to  azure-blue.  Streak  greenish -blue.  Q.  ratio  R  :  K  :  Si 
=  1:2:6;  formula  R3Al2Si9O27,  with  R=Fe,Mg,Ca.Na2.  Analysis,  Striiver,  Si02  58 '55, 
A103  21-40,  FeO  9 '04,  MgO  3 '92,  CaO  2 "03,  Na2O  4-77,  K20  tr=99'71.  Occurs  in  chlorite 
slate  in  the  valleys  of  Aosta  and  Looano. 

GLAUCOPHANE. — Monoclinic.    Cleavage  prismatic,  1  A  1— 124°  51'.    H.— 6'5.    G.  =3 '0907. 


OXYGEN    COMPOUNDS — ANHYDROUS    SILICATES. 


277 


Color  blue,  bluish-black.     Q.   ratio  for  bases  to  silicon  1  :  2.     Analysis  from  Zermatt,   by 
Bodewig,  SiO,  57-81,  M08  12'03,  FeO3  217,   FeO  5'78,  MgO  13'07,  CaO  2'20,  Na20  7'33 
=  100-45.     Also  from  island  of  Syra. 
WICHTISITE,  Finland. — Perhaps  identical  with  glaucophane. 


BERYL. 


Hexagonal.      0  A 1  =  150°  3' ;  c  —  0-499.     Habit  prismatic,  the  prism 

basal  imperfect ;  lateral   indistinct. 


532 


often  vertically  striated.      Cleavage 
Occasionally  coarse  columnar  and 
large  granular. 

H.  =  7-5-8.  G.  =  2-63-2-76. 
Lustre  vitreous,  sometimes  resin- 
ous. Color  emerald-green,  pale 
green,  passing  into  light-blue,  yel- 
low, and  white.  Streak  white. 
Transparent  —  subtranslucent. 
Fracture  conchoidal,  uneven.  Brit- 
tle. Double  refraction  feeble ; 
axis  negative. 

„         m,.  .      .  ,,  ,,     ,,       ,.    .  Haddam,  Ct.  Siberia. 

Var. — This  species  is  one  of  the  few  that 

occur  only  in  crystals,  and  that  have  no  es- 
sential variations  in  chemical  composition.  There  are,  however,  two  prominent  groups  depend- 
ent on  color,  the  color  varying  as  chrome  or  iron  is  present ;  but  only  the  merest  trace  of  either 
exists  in  any  case.  The  crystals  are  usually  oblong  prisms.  1.  Emerald.  Color  bright 
emerald-green,  owing  to  the  presence  of  chromium.  Hardness  a  little  less  than  for  beryl, 
according  to  the  lapidaries.  2.  Beryl.  Colors  those  of  the  species,  excepting  emerald-green, 
and  due  mainly  to  iron.  The  varieties  of  beryl  depending  on  color  are  of  importance  in  the 
arts,  when  the  crystals  are  transparent  enough  to  be  of  value  as  gems."  The  transparent 
bluish-green  kinds  are  called  aquamarine;  also  apple -green  ;  greenish-yellow  to  iron-yel- 
low and  honey-yellow.  Davidsouite  is  nothing  but  greenish-yellow  beryl  from  near  Aberdeen ; 
aud  goiJienite  is  a  colorless  or  white  variety  from  Goshen,  Mass. 

Comp— Be3MSi6O,8=Silica  6tr8,  alumina  191,  glucina  14-1=100. 

Pyr,,  etc. — B.B.  alone  unchanged  or  becomes  clouded;  at  a  high  temperature  the  edges 
are  rounded,  and  ultimately  a  vesicular  scoria  is  formed.  Fusibility =5 "5  (Kobell).  Glass 
with  borax  clear  and  colorless  for  beryl,  a  fine  green  for  emerald.  Slowly  soluble  with  salt 
of  phosphorus  without  leaving  a  siliceous  skeleton.  A  yellowish  variety  from  Broddbo  and 
Finbo  yidlds  with  soda  traces  of  tin.  Unacted  upon  by  acids. 

DifL — Distinguished  from  apatite  by  its  hardness,  not  being  scratched  by  a  knife,  also 
harder  than  green  tourmaline  ;  from  chryso'oeryl  by  its  form,  and  from  euclase  and  topaz  by 
its  imperfect  cleavage  ;  never  massive. 

Obs. — Emeralds  occur  in  clay  slate,  in  isolated  crystals  or  in  n°sts  (not  in  veins),  near  Muso, 
etc. ,  in  N.  Granada ;  in  Siberia.  Transparent  beryls  (aquamarines)  are  found  in  Siberia, 
Hindostan,  and  Brazil.  Beautiful  crystals  also  occur  at  Elba  ;  Ehrenfriedersdorf  ;  Schlacken- 
wald  ;  at  St.  Michael's  Mount  in  Cornwall ;  Limoges  hi  France ;  in  Sweden  ;  Fossuni  in  Nor- 
way ;  and  elsewhere. 

Beryls  of  gigantic  dimensions  have  been  found  in  the  United  States,  in  N.  Hamp.,  at 
Acworth  and  Grafton,  and  in  Mass..  at  Royalston  ;  but  they  are  mostly  poor  in  quality.  A 
crystal  from  Grafton,  according  to  Prof.  Hubbard,  measures  45  in.  by  24  in  its  diameter,  and 
a  single  foot  in  length  by  calculation  weighs  1,076  Ibs.,  making  it  in  all  nearly  2^  tons. 
Other  localities  are  in  Mass.,  at  Barre;  at  Goshen;  at  Chesterfield.  In  Conn.,  at  Haddam; 
Middletown  ;  at  Madison.  In  Penn. ,  at  Leiperville  and  Chester  ;  at  Mineral  Hill. 

ECDIALYTE. — Rhombohedral.  Color  rose-red.  Exact  composition  uncertain.  Analysis, 
Damour,  SiO2  50 '38,  ZrO2  15-60,  Ta,O6  v)'35,  FeO  6 "37,  MnO  1-61,  C.iO  9 '23,  Na2O  13-10, 
Cl  1'48,  H,O  1-25=99-37.  West  Greenland.  EUCOLITE  is  similar,  but  contains  also  some 
of  the  cerium  metals.  Norway. 

POLLUTE.— SRjitiSiida  +  Saq  with  R  —  mostly  Cs(Na.Li).  If  Na  :  Cs=l  :  2,  then 
SiO*  42-6,  ^1O3  1»'2,  Cs.O  33 '4,  Na2O  3-7,  H,O  2-1  =  100.  Isometric.  Colorless.  Island  of 
Elba  with  castorite. 


278 


DESCRIPTIVE   MINERALOGY. 


/S.  UNISILICATES.     GENERAL   FORMULA 
Chrysolite  Group. 

CHRYSOLITE.     Olivine.     Peridot. 


Orthorhombic.     /A  7=  94°  2' 


533 


534 


it 


If 


0  A  14=128°  28';  c:  b: 
1-0729  :  1.  <9  A  l-£  =  130° 
A  i-2,  ov.  i-i,  =  130°  2'.  Cleavage  : 
*-#  rather  distinct.  Massive  and 
compact,  or  granular ;  usually  in 
imbedded  grains. 

H.  =  6-7.  G.= 3-33-3-5.  Lustre 
vitreous.  Color  green — commonly 
olive-green,  •  sometimes  yellow, 
brownish,  grayish- red,  grayish- 
green.  Streak  usually  uncolored, 
rarely  yellowish.  Transparent- 
translucent.  Fracture  couchoidal. 


Oomp.,  Var. — (Mg,Fe)2SiO4,  with  traces  at  times  of  Mn,  Ca,  Ni.  The  amount  of  iron 
varies  much.  If  Mg  :  Fe=12  :  1,  the  formula  requires  Silica  41 '39, .  magnesia  50-90,  iron 
protoxide  7*71=100  ;  Mg-  :  Fe=9  :  1,  6  :  1,  etc.,  and  in  Jiyalosiderite  2:1. 

Fyr.,  etc. — B.B.  whitens,  but  is  infusible  ;  with  the  fluxes  gives  reactions  for  iron.  Hya- 
losiderite  and  other  varieties  rich  in  iron  fuse  to  a  black  magnetic  globule.  Some  varieties 
give  reactions  for  titanium  and  manganese.  Decomposed  by  hydrochloric  acid  with  separa- 
tion of  gelatinous  silica. 

Diff. — Distinguished  by  its  infusibility.  Commonly  observed  in  small  yellow  imbedded  grains. 

Obs. — A  common  constituent  of  some  eruptive  rocks  ;  and  also  occurring  in  or  among  ineta- 
morphic  rocks,  with  talcose  schist,  hypersthene  rocks,  and  serpentine  ;  or  as  a  rock  formation ; 
also  a  constituent  of  many  meteorites  (e.g.,  the  Pallas  iron). 

Occurs  in  eruptive  rocks  at  Vesuvius,  Sicily,  Hecla,  Sandwich  Islands,  and  most  volcanic 
islands  or  regions  ;  in  Auvergne  ;  at  Unkel,  on  the  Rhine ;  at  the  Laacher  See  ;  in  dolerite  or 
basalt  in  Canada.  Also  in  labradorite  rocks  in  the  White  Mountains,  N.  H.  (hyatosiderite)  ;  in 
Loudon  Co.,  Va. ;  in  Lancaster  Co.,  Pa.,  at  Wood's  Mine. 

The  following  are  members  of  the  Chrysolite  Group  : 

FORSTERITE. — Mg2Si04.  Like  chrysolite  in  physical  characters.  Vesuvius.  BOLTONITE, 
essentially  the  same.  Bolton,  Mass: 

MONTICELLITE,  from  Mt.  Somma,  and  BATRACIIITE,  from  the  Tyrol,  are  (Ca,Mg)2Si04, 
with  Ca  :  Mg=l  :  1.  H.  =5-5 '5.  G.  =3 '03-3 -25.  Monticellibe  also  occurs  in  large  quantities 
(v.  Rath)  on  the  Pesmeda  Alp,  Tyrol,  altered  to  serpentine  and  fassaite. 

FAYALITE. — Fe2SiO4.  G.  =4-4'14.  Color  black.  In  volcanic  rocks  at  Fayal,  Azores ; 
Mourne  Mts.,  Ireland. 

HORTONOLITE.— (Fe,Mg)2SiO4,  with  Fe  :  Mg=3  :  2.     O'Neil  mine,  Orange  Co.,  N.  Y. 

TEPHROITE-— Mn2SiO4.    G.  =4-4'12.    Color  reddish-brown.     Sterling  Hill,  N".  J.;  Sweden. 

ROEPPERITE. — An  iron-manganese-zinc  chrysolite.  H.=5'5-6.  G.  =3 '95-4 -08.  Color 
dark-green  to  black.  Stirling  Hill,  N.  J. 

KNEBELITJE. — (Fe,Mn)2SiO4,  with  Fe  :  Mn=l  :  1.     G.=4'12.     Color  gray.     Dannemora. 


LEUCOPHANITE. — Composition  given  by  the  analysis  (Ramm.)  SiOa  47 '03,  A1O3  1'03,  BeO 
10-70,  CaO  23-37,  MgO  0'17,  Na:O  11-20,  K,0  0'30,  F  6-57=100'43.  Orthorhombic.  G.  = 
2 '97.  Color  greenish-yellow.  Occurs  in  syenite  on  the  island  of  Lamoe,  Norway. 

MELIPIIANITE  (Melinophan). — Composition  given  by  the  analysis  (Ramm.)  SiO2  43'66, 
AlO8(FeOs)  1-57,  BeO  11 '74,  CaO  20-74,  MgO  O'll,  Na20  8'55,  K.O  1'40,  H2O  0'30,  F  5 '73 
=99-80.  G.=3'018.  Orthorhombic.  Color  yellow.  Fredriksviirn,  Norway. 

WOHLERITE.— Composition  given  by  the  analysis  (Ramm.)  SiO2  28 -43,  Cb205'14-41,  ZrO2 
19-63,  CaO  26-18,  FeO(MnO;  2'50,  Na20  7'78=98'93.  Monoclinic.  G.=3'41.  Color  light- 
yellow.  Near  Brevig,  Norway. 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


279 


Willemite    Group. 


WILLEMITE. 

Ehombohedral.  R  A  E  =  116°  1',  O  A  E  =  142°  17' ;  c  =  0-67378. 
age :  i-%  easy  in  X.  Jerse}7  crystals ;  O  easy  in  those  of  Moresnet. 
massive  and  in  disseminated  grains.  Sometimes  fibrous. 

H.=5-5.     G.=3-89-4-18  ;  4-27,  transparent  crystals  535 

(Cornwall).  Lustre  vitreo-resinous,  rather  weak.  Color 
whitish  or  greenish-yellow,  when  purest ;  apple-green, 
flesh-red,  grayish-white,  yellowish-brown ;  often  dark- 
brown  when  impure.  Streak  uncolored.  Transparent 
to  opaque.  Brittle.  Fracture  conchoidal.  Double 
refraction  strong ;  axis  positive. 


Cleav- 
Also 


Var. — The  crystals  of  Moresnet  and  New  Jersey  differ  in  occurring 
forms.  The  latter  are  often  quite  large,  and  pass  under  the  name  of 
troostite ;  they  are  commonly  impure  from  the  presence  of  man- 
ganese and  iron. 

Comp.— ZnoSi04=Silica  27-1,  zinc  oxide  72 -9=100. 

Pyr.,  etc. — B.B.  in  the  forceps  glows  and  fuses  with  difficulty  to 
a  white  enamel ;  the  varieties  from  New  Jersey  fuse  from  3  '5  to  4. 
The  powdered  mineral  on  charcoal  in  R.F.  gives  a  coating  yellow 

while  hot  and  white  on  cooling,  which,  moistened  with  solution  of  cobalt,  and  treated  in  O. 
F. ,  is  colored  bright  green.  With  soda  the  coating  is  more  readily  obtained.  Decomposed 
by  hydrochloric  acid  with  separation  of  gelatinous  silica. 

Obs. — From  Vieille-Montagne  near  Moresnet ;  also  at  Stolberg  ;  at  Raibel  in  Carinthia  ; 
at  Kucsaina  in  Servia,  and  in  Greenland.  In  New  Jersey,  at  both  Franklin  and  Stirling  in 
such  quantity  as  to  constitute  an  important  ore  of  zinc.  It  occurs  intimately  mixed  with 
zincite  and  franklinite,  and  is  found  massive  of  a  great  variety  of  colors,  from  pale  honey- 
yellow  and  light  green  to  dark  ash-gray  and  flesh-red  ;  sometimes  in  crystals  (troostite). 


DIOFTASE.    Emerald-Copper. 

Ehombohedral;   tetartohedral.     72  A  72  =126°  24';   O  A  E  =148°  38'; 
c  =  0-5281.     Cleavage:  R  perfect.     Twins:  twinning- 
plane  R.     Also  massive. 

1I.=5.  G.=3-278-3-348.  Lustre  vitreous.  Color 
emerald-green.  Streak  green.  Transparent — subtrans- 
lucent.  Fracture  conchoidal,  uneven.  Brittle.  Double 
refraction  strong,  positive. 

Comp. — Q.  ratio  for  Cu  :  Si  :  H=l  :  2  :  1;  formula  H2CuSiO4 
(Ramm.)  =  Silica  38 1,  copper  oxide  50-4,  water  11-5=100. 

Pyr.,  etc. — In  the  closed  tube  blackens  and  yields  water.  B.B. 
decrepitates,  colors  the  flame  emerald-green,  but  is  infusible.  With 
the  fluxes  gives  the  reactions  for  copper.  With  soda  on  charcoal  a 
globule  of  metallic  copper.  Decomposed  by  acids  with  gelatinization. 

Obs. — Dioptase  occurs  disposed  in  well-defined  crystals  and  amor- 
phous on  quartz,  occupying  seams  in  a  compact  limestone  west  of  the 
hill  of  Altyn-Tubeh  in  the  Kirghese  Steppes ;  also  in  the  Siberian 
gold-washings.  Also  reported  as  found  in  the  Duchy  of  Nassau,  be- 
tween Oberlahnstein  and  Braubach. 

PIIENACITE.— Be2Si04.    Ehombohedral.    Colorless.    Kesembles  quartz.    Takovaja ;  Miask ; 
Durango,  Mexico. 


280  DESCRIPTIVE   MINERALOGY. 

FRIEDELITE.— Rhombohedral.  0  A  72=147°;  R  A  72=123°  42'.  Cleavage:  0  easy. 
H.=4.75.  Gr.=8.07.  Also  massive,  saccharoidal.  Color  rose-red.  Translucent.  Double 
refraction  strong,  axis  negative.  Analysis,  Si02  36.12,  MnO  (FeO  tr)  53 '05,  MgO,  CaO  2-96, 
H2O  7-87=100.  This  corresponds  to  the  formula  Mn4Si3O10  +  2HoO.  Tf  the  water  is  basic, 
as  in  dioptase,  with  which  it  seems  to  be  related  in  form,  the  formula  is  H4Mn4Si3Oi2  = 
R,SiO4.  This  requires  SiO2  36'00,  MnO  56*80,  H2O  7*20=100.  Occurs  with  diallogite  and 
alabandite  at  the  manganese  mine  of  Adervielle,  Hautes-Pyrenees.  (Bertrand,  C.  11.,  May, 
1876.) 


HELVITE. 

Isometric :  tetrahedral.     Cleavage  :  octahedral,  in  traces. 

H.== 6-0-5.  G.  =  3-1-3*3.  Lustre  vitreous,  inclining  to  resinous.  Color 
honey-yellow,  inclining  to  yellowish-brown,  and  siskin-green.  Streak  un- 
colored.  Subtranslucent.  Fracture  uneven. 

Comp.— Q.  ratio  for  R  :  Si=l  :  2  ;  for  Mn  +  Fe  :  Be  =  l  :  1 ;  formula  3(Be.Mn,Fe)2Si04-f- 
(Mn.Fe)S  (Ramm.).  Analysis  by  Teich,  Lupikko,  Finland,  Si02  30 '31,  BeO  10-51,  MnO 
37-87,  FeO  10-37,  CaO  4-72,  ign  0-22=99-95. 

Pyr.,  etc. — Fuses  at  3  in  R.F.  with  intumescence  to  a  yellowish-brown  opaque  bead,  becom- 
ing darker  in  R.F.  With  the  fluxes  gives  the  manganese  reaction.  Decomposed  by  hydro- 
chloric acid,  with  evolution  of  sulphuretted  hydrogen,  and  separation  of  gelatinous  silica. 

Obs. — Occurs  in  gneiss  at  Schwarzenberg  in  Saxony  ;  at  Breitenbrunn,  Saxony ;  at  Horte- 
kulle  near  Modum,  and  also  at  Brevig  in  Norway,  in  zircon-syenite. 

DANALITE. 

Isometric.  In  octahedrons,  with  planes  of  the  dodecahedron ;  the  dode- 
cahedral  faces  striated  parallel  to  the  longer  diagonal. 

H.=r5'5-6.  G.  =  3'427.  Lustre  vitreo-resinous.  Color  flesh-red  to  gray. 
Streak  similar,  but  lighter.  Translucent.  Fracture  subconchoidal,  uneven. 
Brittle. 

Comp — 3(Be,Fe,Mn,Zn)2SiO4  +  (Fe,Mn,Zn)S.  Analysis  :  J.  P.  Cooke,  Rockport,  SiOo 
31-73,  FeO  27 "40,  MnO  6'28,  ZnO  17 '51,  BeO  13  -83,  S  5 '48= 102 '23.  By  subtracting  from 
the  analysis  oxygen  2 '74,  equivalent  to  the  sulphur,  the  sum  is  99-49. 

Pyr.,  etc. — B.B.  fuses  readily  on  the  edges  to  a  black  enamel.  With  soda  on  charcoal  gives 
a  slight  coating  of  zinc  oxide.  Perfectly  decomposed  by  hydrochloric  acid,  with  evolution  of 
sulphuretted  hydrogen  and  separation  of  gelatinous  silica. 

Obs. — Occurs  in  the  Rockport  granite,  Cape  Ann,  Mass. ,  small  grains  being  disseminated 
through  this  rock ;  also  near  Gloucester,  Mass.  , 

EULYTITE  (Kieselwisoiuth,  Germ.). — Isometric,  tetrahedral;  in  minute  crystals  often 
aggregated  together.  H.  =4-5-5.  G.  =6 -106.  Color  grayish-white  to  brown.  Comp.  A  uni- 
silicate  of  bismuth,  Bi4Si3Oi2.  Schneeberg.  Agricolite.  Composition  similar,  but  form 
monoclinic.  Occurs  in  globular  masses  having  a  radiated  structure,  and  in  indistinct  groups 
of  crystals.  Schne.eberg  (color  hair-brown)  and  Johanngeorgenstadt  (color  wine-yellow). 

BISMUTOFERRITE.— Cryptocrystalline;  generally  massive.  H.=3'5.  G.=4-47.  Color 
olive-green.  Analysis  (Frenzel)  SiO2  24 '05,  FeO3  33-12,  Bi2O3  42-83=100.  Schneeberg. 
Hypocldorite  is  hornstone  mixed  with  the  above  mineral  and  other  impurities. 


Garnet    Group. 
GARNET.    Granat,  Germ. 

Isometric;    dodecahedron,  f.  537,  and  the    trapezohedron   2-2,   f.    538, 
the  most  common  forms ;   octahedral   form    very   rare.     Distorted  forms 


OXYGEN    COMPOUNDS ANHYDROUS    SILICATES. 


281 


shown  in  f.  345-352,  pp.  105,106.  Cleavage:  dodecahedral,  sometimes  quite 
distinct.  Twins :  twinning-plane  octahedral.  Also  massive ;  granular, 
coarse,  or  fine,  and  sometimes  friable ;  lamellar,  lamellae  thick  and  bent. 
Also  very  compact,  crypto-crystalline  like  saussurite. 


539 


H.  =  6'5-7'5.  G.=3*15-4-3.  Lustre  vitreous — resinous.  Color  red, 
brown,  yellow,  white,  apple-green,%  black;  some  red  and  green  colors  often 
bright.  Streak  white.  Transparent — subtranslucent.  Fracture  subcon- 
choiclal,  uneven.  Brittle,  and  sometimes  friable  when  granular  massive; 
very  tough  when  compact  cryptocrystalline.  Sometimes  doubly  refracting 
in  consequence  of  lamellar  structure,  or  in  some  cases  from  alteration. 

Comp.,  Var. — Garnet  is  a  unisilicate  of  elements  in  the  sesquioxide  and  protoxide  states, 
having  the  general  formula  R3ftSi3Oi2.  There  are  three  prominent  groups,  based  on  the 
nature  of  the  predominating  sesquioxide. 

I.  ALUMINA  GARNET,  in  which  aluminum  (Al)  predominates. 

II.  IRON  GARNET,  in  which  iron  (Fe)  predominates,  usually  with  some  aluminum. 

III.  CHROME  GARNET  in  which  chromium  (-Gr)  is  most  prominent. 

There  are  the  following  varieties  or  subspecies,  based  on  the  predominance  of  one  or  another 
of  the  protoxides  : 

A.  GROSSULARITE,  or  Lime-Alumina  garnet.  B.  PYROPE,  or  Magnesia- Alumina  garnet. 
C.  ALMA*TDITE,  or  Iron- Alumina  garnet.  D.  SPESSARTITK,  or  Manganese- Alumina  gar  net. 
E.  ANDRADJTE,  or  Lime-Iron  garnet,  including  1,  ordinary;  2,  manganesian,  or  Rothoffite  : 
8,  yttriferous,  or  Yttcr-garnet*  F.  BREDUERGITE,  or  Lime-Magnesia-Iron  garnet.  G. 
OUVAROVITE,  or  Lime- Chrome  garnet.  Excepting  the  last,  these,  subdivisions  blend  with  one 
another  more  or  less  completely. 

A.  Li  me- Alumina  gar  net ;  G-ROSSULARITE.    Cinnamon  stone.  A  silicate  mainly  of  aluminum 
and  calcium  ;  formula  mostly  Ca3iVlSi3012  —  Silica  40'0,  alumina  22 '8,  lime  87-2=100.     But 
some  calcium  often  replaced  by  iron,  and  thus  graduating  toward  the  Almandite  group.    Color 
(a)  white ;  (b)  pale  green ;  (c)  amber-  and  honey-yellow ;   (d)  wine-yellow,  brownish-yellow, 
cinnamon-brown;  rarely  (e)  emerald-green  from  the  presence  of  chromium.     G-.  =3'4-3'75. 

B.  Mr  gnesia- Alumina  garnet;  PYROPE.     A  silicate  of  aluminum,  with  various  protoxide 
bases,  among  which  magnesium  predominates  much  in  atomic  proportions,  while  in  small  pro- 
portion in  other  garnets,  or  absent.     Formula  (Mg,Ca,Fe,Mn)3MSi3Oi2.     The  original  pyrope 
is  the  kind  containing  chromium.     In  the  analysis  of  the  Arendal  magnesia-garnet,  Mg  :  Ca  : 
Fe+Mn=3  :  1  :  2;   Si02  42'4o,  A103  22'47,  FeO  9  29,  MnO  6'27,  MgO  13'43,  CaO  (>'53  = 
100-44  Wacht.     G-.  =3 "157.     The  name  pyrope  is  from  Trvpw-fc,  fire-like. 

C .  Iron- Alumina  garnet ;  ALMANDITE.     A  silicate  mainly  of  aluminum  and  iron  (Fe) ; 
formula   Fe^lSisO^^  Silica  36-1,  alumina  20'6,  iron  protoxide  43-3=100;  or  Mn  may  re- 
place some  of  the  Fe,  and  F-e  part  of  the  Al.     Color  fine  deep-red  and  transparent,  and  then 
c  died  precious  garnet ;  also  brownish-red  and  translucent  or  subtranslucent,  common  garnet; 
black,  and  then  referred  to  var.  mefanite.     Part  of  common  garnet  belongs  to  the 

group,  or  is  iron  garnet. 


282  DESCRIPTIVE   MINERALOGY. 

D.  Manganese- Alumina  garnet;   SPESSAKTITE.     Color  dark  hyacinth-red  (fr.  Spessart), 
sometimes  with  a  shade  of  violet,  to  brownish-red.     G.  =3*7-4 '4.     Analysis,  Haddam,   Ct., 
SiO,  36-16,  A1O3  19*76,  FeO  11 '10,  MnO  82 -18,  MgO  0'22,  CaO  0*58=100,  Ramm.. 

E.  Lime-Iron  garnet ;   ANDRADITE.     Aplome.     Color   various,    including  wine-,  .topaz-, 
and  greenish-yellow  (topazolite),  apple-green,  brownish -red,  brownish -yellow,  grayish-green, 
dark  green,  brown,  grayish-black,  black.     G. =3. 64-4. 

Comp. — Ca3FeSisOi2,  this  includes :  (a)  Topazolite,  having  the  color  and  transparency  of 
topaz,  and  also  sometimes  green ;  although  resembling  essonite,  Damour  has  shown  that  it 
belongs  here,  (b)  Colophonite,  a  coarse  granular  kind,  brownish-yellow  to  dark  reddish- 
brown  in  color,  resinous  in  lustre,  and  usually  with  iridescent  hues ;  named  after  the  resin 
colophony,  (c)  Melanite  (named  from  ^e'Aaq,  black),  black,  either  dull  or  lustrous;  but  all 
black  garnet  is  not  here  included.  Pyreneite  is  grayish-black  melanite  ;  the  original  afforded 
Vauquelin  4  p.  c.  of  water,  and  was  iridescent,  indicating  incipient  alteration,  (d)  Dark  green 
garnet,  not  distinguishable  from  some  allochroite,  except  by  chemical  means. 

F.  Lime- Magnesia  Iron  garnet :  BREDBERGITE.     A  variety  from   Sala,  Sweden,  is  here 
included.     Formula  (Ca,Mg)3FeSi3Oi2  =  Silica  37 '2,  iron  sesquioxide  33' 1,  magnesia  12-4, 
lime  17'3=100.     It  corresponds  under  Iron  garnet  nearly  to  aplome  under  Alumina  garnet. 

G.  Lime-  Chrome  garnet  ;  OUVAROVITE.      A  silicate  of  calcium  and  chromium.      Formula 
Ca36rSi3Oi2.     In  the  Ural  variety,  a  fourth  of  the  chromium  oxide  is  replaced  by  aluminum 
oxide  ;  that  is,  Al  :  6r=l  :  3  nearly.     Color  emerald-green.    H.=7'5.    G.  =3 '41-3 '52.    B.B. 
infusible ;  with  borax  a  clear  chrome-green  glass.     Named  after  the  Russian  minister,  Uvarof . 

Pyr.,  eto. — Most  varieties  fuse  easily  to  a  light-brown  or  black  glass  ;  F.  =3  in  almandite, 
spessartite,  grossularite,  and  allochroite  ;  3  '5  in  pyrope ;  but  ouvarovite  is  almost  infusible, 
F.=6.  Allochroite  and  almandite  fuse  to  a  magnetic  globule.  Reactions  with  the  fluxes 
vary  with  the  bases.  Almost  all  kinds  react  for  iron  ;  strong  manganese  reaction  in  spessar- 
tite,  and  less  marked  in  other  varieties ;  a  chromium  reaction  in  ouvarovite,  and  in  most  py- 
rope. Some  varieties  are  partially  decomposed  by  acids ;  all  exce'pt  ouvarovite  are  decomposed 
after  ignition  by  hydrochloric  acid,  and  generally  with  separation  of  gelatinous  silica.  Decom- 
posed on  fusion  with  alkaline  carbonates. 

3319", — Ordinary  garnets  are  distinguished  from  zircon  by  their  fusibility  B.B.,  but  they  fuse 
less  readily  than  vesuvianite  ;  the  vitreous  lustre,  absence  of  prismatic  structure,  and  usually 
the  form,  are  characteristic;  it  has  a  higher  specific  gravity  ttan  tourmaline. 

Obs. — Garnet  crystals  are  very  common  in  mica  schist,  gnt  iss,  syenitic  gneiss,  and  horn- 
blende and  chlorite  schist ;  they  occur  often,  also,  in  granite,  syenite,  crystalline  limestones, 
sometimes  in  serpentine,  and  occasionally  in  trap  and  volcanic  tufa  and  lava. 

Some  localities  are:  Cinnamon-stone  (Essonite),  Ceylon;  Mussa-Alp  in  Piedmont. 
Orossidarite,  Siberia;  Tellemark,  Norway;  Ural.  Almandite,  Ceylon,  Pegu,  Brazil,  and 
Greenland.  Common  garnet  in  large  dodecahedrons,  Sweden ;  Arendal  and  Kongsberg  in 
Norway,  and  the  Zillerthal.  Mtlanite  at  Vesuvius  and  in  the  Hautes-Pyrenees  (Pyreneite}. 
Aplome  at  Schwarzenberg  in  Saxony.  Spessartite  at  Spessart  in  Bavaria,  Elba,  at  St.  Marcel, 
Piedmont.  Pyrope  in  Bohemia,  also  at  Zoblitz  in  Saxony.  Ouvaromte  in  the  Urals. 

In  N.  America  in.  Maine,  Phippsburg,  Rumford,  Windham,  at  Brunswick,  etc.  In  N.  Ilamp., 
Warren.  In  Mass.,  at  Carlisle;  massive  at  Newbury  ;  at  Chesterfield.  In  Conn.,  trapezo- 
hedrons,  •£-!  in. ,  in  mica  slate,  at  Reading  and  Monroe  ;  Haddam.  In  _ZV.  York,  at  Roger's 
Rock ;  Crown  Point,  Essex  Co. ;  at  Amity.  In  JV".  Jersey,  at  Franklin.  In  Penn. ,  in  Chester 
Co.,  at  Pennsbury ;  near  Knauertown,  at  Keims'  mine  ;  at  Chester,  brown;  in  Leiperville, 
red;  near  Wilmington.  In  California,  in  Los  Angeles  Co.,  in  Mt.  Meadows;  ouvarovite  at 
New  Idria ;  pyrope,  near  Santa  Fe,  New  Mexico.  In  Canada,  at  Marmora,  at  Grenville  ; 
chrome -garnet  in  Orford,  Canada. 

The  cinnamon-stone  from  Ceylon  (called  hyacinth)  and  the  precious  garnet  are  used  as  gems 
when  large,  finely  colored,  and  transparent.  The  stone  is  cut  quite  thin,  on  account  of  the 
depth  of  color,  with  a  pavilion  cut  below,  and  a  broad  table  above  bordered  with  small  facets. 
An  octagonal  garnet  measuring  8|  lines  by  6-J  has  sold  for  near  $700.  Pulverized  garnet  is 
sometimes  employed  as  a  substitute  for  emery. 


Vesuvianite  Group. 
ZIRCON. 


Tetragonal.  0  A  1-i  =  147°  22' ;  c  =  0-640373,  Haidinger.  /A  1  = 
132°  10 .  Faces  of  pyramids  sometimes  convex.  Cleavage :  /  imperfect, 
1  less  distinct.  Also  in  irregular  forms  and  grains. 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


283 


H.=7'5.  G-.  =4'05-4-75.  Lustre  adamantine.  Colorless,  pale  yellow- 
ish, grayish,  yellowish-green,  brownish-yellow,  reddish-brown.  (Streak  un- 
eoloredi  Transparent  to  subtranslucent  and  opaque.  Fracture  conchoidal, 
brilliant.  Double  refraction  strong,  positive. 


541 


545 


546 


Saualpe. 


McDowell  Co.,  N.  C. 


Var. — The  colorless  and  yellowish  or  smoky  zircons  of  Ceylon  have  there  been  long  called 
jargons  in  jewelry,  in  allusion  to  the  fact  that,  while  resembling  the  diamond  in  lustre,  they 
were  comparatively  worthless  ;  and  thence  came  the  name  zircon.  The  brownish,  orange,  and 
reddish  kinds  were  called  distinctively  hyacinths — a  name  applied  also  in  jewelry  to  some  topaz 
and  light-colored  garnet. 

Comp.— ZrSiO4  =  Silica  33,  zirconia  67=100.  Klaproth  discovered  the  earth  zirconia  in 
this  species  in  1789. 

Pyr.,  etc. — Infusible  ;  the  colorless  varieties  are  unaltered,  the  red  become  colorless,  while 
dark-colored  varieties  are  made  white  ;  some  varieties  glow  and  increase  in  density  by  igni- 
tion. Not  perceptibly  acted  upon  by  salt  of  phosphorus.  In  powder  is  decomposed  when 
fused  with  soda  on  the  platinum  wire,  and  if  the  product  is  dissolved  in  dilute  hydrochloric 
acid  it  gives  the  orange  color  characteristic  of  zirconia  when  tested  with  turmeric  paper.  Not 
acted  upon  by  acids  except  in  fine  powder  with  concentrated  sulphuric  acid.  Decomposed 
by  fusion  with  alkaline  carbonates  and  bisulphates. 

Diff. — Distinguished  by  its  adamantine  lustre,  hardness,  and  infusibility  ;  the  occurrence  of 
square  prismatic  forms  is  also  characteristic. 

Obs. — Occurs  in  crystalline  rocks,  especially  granular  limestone,  chloritic  and  other  schists  ; 
gneiss,  syenite  ;  also  in  granite  ;  sometimes  in  iron-ore  beds. 

Found  in  alluvial  sands  in  Ceylon  ;  in  the  gold  regions  of  the  Ural ;  at  Arendal  in  Norway  ; 
at  Fredericks  varn,  in  zircon-syenite ;  in  Transylvania  ;  at  Bilin  in  Bohemia. 

In  N.  America,  in  JV.  York,  at  Moriah,  Essex  Co. ,  and  in  Orange  Co. ;  in  Warwick  ;  near 
Amity  ;  at  Diana  in  Lewis  Co. ;  also  at  Rossie.  In  2T.  Jersey,  at  Franklin ;  at  Trenton  in 
gneiss.  In  N.  Car.,  in  Buncombe  Co.;  in  the  sands  of  the  gold  washings  of  McDowell  Co. 
In  California,  in  the  auriferous  gravel  of  the  north  fork  of  the  American  river,  and  else- 
where. In  Canada,  at  Grenville,  etc. 


VESUVIANITE.    IDOCRASE. 

Tetragonal.  O  A  \4  =  151°  45' ;  c  =  0-537199  (v.  Kokscharof).  O  A  1 
=  142°  46i'  1  A  1,  ov.  1-i,  =  129°  21'.  Cleavage :  I  not  very  distinct,  O 
still  less  so.  Columnar  structure  rare,  straight  and  divergent,  or  irregular. 
Sometimes  granular  massive.  Prisms  usually  terminating  in  the  basal  plane 
O ;  rarely  in  a  pyramid  or  zirconoid ;  sometimes  the  prism  nearly  wanting, 
and  the  form  short  pyramidal  with  truncated  summit  and  edges. 


284 


DESCRIPTIVE   MINERALOGY. 


551 


G.  =  3-34:9-3 -45.      Lustre    vitreous;    often    inclining   to    re- 

iuous.  Color  brown  to  green, 
and  the  latter  frequently  bright 
and  clear ;  occasionally  sulphur- 
yellow,  and  also  pale  blue  ;  some- 
times green  along  the  axis, 
and  pistachio-green  transversely. 
Streak  white.  Subtransparent — 
faintly  subtranslucent.  Fracture 
subconchoidal — uneven.  Double 
refraction  feeble,  axis  negative. 


Comp.,  Var, — Q.  ratio  for  R  :  R-  :-  Si= 
4:3:7  (according  to  the  latest  investi- 
gations of  Rammelsberg).  R— Ca  (also 
Mg,  Fe,  orH2,K2,Na2);  R=A1  and  also  Pe. 
If  we  neglect  the  water  the  empirical  for- 


2  X 


Sandford,  Me. 


mula  is  R8R2Si7O28,  where  the  quantivalent  ratio  of  bases  to  silicon  is  1  :  1.  The  ratio  of 
R  :  ft  varies  much,  which,  as  stated  by  Rammelsberg,  is  the  explanation  of  the  different 
varieties.  Analyses  by  Rammelsberg.  (1)  Monzoni ;  (2)  Wilui,  Siberia. 


(1) 
(2) 


SiOa 
37-32 
38-40 


16-08 
13-72 


FeO3 

3-75 

5-54 


FeO 
2-91 


MgO 
2-11 

6-88 


CaO 

35-34 

35-04 


Na20(K2O) 
016 
0-66 


HoO 

2-08=  99-75 
0.82=101-06. 


Pyr.,  etc. — B.B.  fuses  at  3  with  intumescence  to  a  greenish  or  brownish  glass.  Magnus 
states  that  the  density  after  fusion  is  2  "93-2  945.  With  the  fluxes  gives  reactions  for  iron, 
and  a  variety  from  St.  Marcel  gives  a  strong  manganese  reaction.  Cyprine  gives  a  reaction  for 
copper  with  salt  of  phosphorus.  Partially  decomposed  by  hydrochloric  acid,  and  completely 
when  the  mineral  has  been  previously  ignited. 

Diff. — Resembles  some  brown  varieties  of  garnet,  tourmaline,  and  epidote,  but  its  tetragonal 
form  and  easy  fusibility  distinguish  it. 

Obs. — Vesuvianite  was  first  found  among  the  ancient  ejections  of  Vesuvius  and  the  dolo- 
mitic  blocks  of  Somma.  It  has  since  been  met  with  most  abundantly  in  granular  limestone  ; 
also  in  serpentine,  chlorite  schist,  gneiss,  and  related  rocks.  It  is  often  associated  with  lime- 
garnet  and  pyroxene.  It  has  been  observed  imbedded  in  opal. 

Occurs  at  Vesuvius  ;  at  Ala,  in  Piedmont ;  at  Monzoni  in  the  Fassathal ;  near  Christiansand, 
Norway  ;  on  the  Wilui  river,  near  L.  Baikal ;  in  the  Urals,  and  elsewhere. 

In  N.  America,  in  Maine ,  at  Phippsburg  and  Rumford,  abundant;  Sandford  (f.  551).  In 
N.  York,  at  Amity.  In  N.  Jersey,  at  Newton.  In  Canada,  at  Calumet  Falls ;  at  Grenville. 

MELILITE  from  Capo  di  Bove,  and  HUMBOLDTILITE  from  Mt.  Somma,  are  similar  in  com- 
position. Analysis  of  the  melilite  by  Damour.  SiOa  38  '34,  iUO3  8  '61,  FeO3 10  '02,  CaO  32  '05, 
MgO  6-71,  Na2O  212,  K20  1'51=99'36.  Tetragonal.  Color  honey-yellow. 


Epidote  Group. 

The  species  of  the  Epidote  Group  are  characterized  by  high  specific 
gravity,  above  3  ;  hardness  above  5  ;  fusibility  B.B.  below  4  ;  anisometric 
crystallization,  and  therefore  biaxial  polarization  ;  the  dominant  prismatic 
angle  112°  to  117°  ;  fibrous  forms,  when  they  occur,  always  brittle  ;  colors 
white,  gray,  brown,  yellowish-green,  and  deep  green  to  black,  and  some- 
times reddish. 


The  prismatic  angle  in  zoisite  and  other  orthorhombic  species  is  /A  / ;  but  in  epidote  it  is 
the  angle  over  a  horizontal  edge  between  the  planes  0  and  i-i,  the  orthodiagonal  of  epidote 
corresponding  to  the  vertical  axis  of  zoisite,  as  explained  under  the  latter  species. 


OXYGEN   COMPOUNDS — ANHYDKOUS    SILICATES. 


285 


EPIDOTE,    Pistazite. 

Monoclinic.  C  —  89°  27' ;  £2  A  v2  =  63°  8',  O  A 1-1  =  122°  23' ;  c  :  5  :  d 
=  0-48436  :  0-30719  :  1.  £Ml-i  =  154°  3',  O  A  -l-i  =  154°  15',  i-i  A  -1 
—  101°  48',  a'-*  A  1  =  104°  15'.  Crystals  usually  lengthened  in  the  direc- 
tion of  the  orthodiagonal,  or  parallel  to  i-i;  sometimes  long  acicular. 
Cleavage :  i-i  perfect ;  l-i  less  so.  Twins :  twinning-plane  l-i ;  also  i-i. 
Also  fibrous,  divergent,  or  parallel ;  also  granular,  particles  of  various  sizes, 
sometimes  fine  granular,  and  forming  rock-masses. 


552 


553 


554 


-If 


H.  =  6-7.  G.  =  3'25-3'5.  Lustre  vitreous,  on  i-i  inclining  to  pearly  or 
resinous.  Color  pistachio-green  or  yellowish-green  to  brownish-green, 
greenish -black,  and  black  ;  sometimes  clear  red  and  yellow  ;  also  gray  and 
grayish-white.  Pleuchroism  often  distinct,  the  crystals  being  usually  least 
yellow  in  a  direction  through  l-i  (see  p.  162).  Streak  nncolored,  grayish. 
Subtransparent — opaque;  generally  subtranslucent.  Fracture  uneven. 
Brittle. 


Var. — Epidote  has  ordinarily  a  peculiar  yellowish-green  (pistachio)  color,  seldom  found  in 
other  minerals.  But  this  color  passes  into  dark  and  light  shades — black  on  one  side,  and 
brown  on  the  other.  Most  of  the  brown  and  nearly  all  the  gray  epidote  belongs  to  the  species 
Zoisite  ;  and  the  reddish- brown  or  reddish-black,  containing  much  oxide  of  manganese,  to 
the  species  Piedmontite,  or  Manganepidot ;  while  the  black  is  mainly  of  the  species  AUanite* 
or  Ceriuin-epidote. 

Comp. — Quantivalent  ratio  for  Ca  :  R  :  Si— 4  :  9  :  12,  and  H  :  Ca=l  :  4.  The  formula  is 
then  HaCa-ittsSioOae.  R  is  Fe  or  Al,  the  ratio  varying  from  1  :  2  to  1  :  6.  Analysis,  Unter- 
sulzbach,  Tyrol,  by  Ludwig :  SiO>  37 '83,  rV!O3  22'63,  Fe03  15 '02,  FeO  0'93,  CaO  23'27,  HLO 
2  '05  =  100 '73.  As  first  shown  by  Ludwig,  epidote  contains  about  2  p.  c.  water,  which  is 
given  off  only  at  high  temperatures. 

Pyr.,  etc. — In  the  closed  tube  gives  water  at  a  high  temperature.  B.B.  fuses  with  intumes- 
cence at  3-3  "5  to  a  dark  brown  or  black  mass  which  is  genernally  magnetic.  Reacts  for  iron 
and  sometimes  for  manganese  with  the  fluxes.  Partially  decomposed  by  hydrochloric  acid, 
but  when  previously  ignited,  gelatinizes  with  acid.  Decomposed  on  fusion  with  alkaline'  car- 
bonates. 

Diff. — Distinguished  often  by  its  peculiar  yellowish-green  color ;  yields  a  magnetic  globule, 
B.B.  Prismatic  forms  often  longitudinally  striated,  but  they  have  not  the  angle,  cleavage, 
or  brittleness  of  tremolite. 

Obs. — Epidote  is  common  in  many  crystalline  rocks,  as  syenite,  gneiss,  mica  schist,  horn- 
bleudic  schist,  serpentine,  and  especially  those  that  contain  the  ferriferous  mineral  horn- 
blende. It  often  accompanies  beds  of  magnetite  or  hematite  in  such  rocks.  It  is  sometimes 
found  in  geodes  in  trap ;  and  also  in  sandstone  adjoining  trap  dikes,  where  it  has  been 
formed  by  metamorphism  through  the  heat  of  the  trap  at  the  time  of  its  ejection.  It  also 
occurs  at  times  in  nodules  in  different  quartz-rorks  or  altered  sandstones.  It  is  associated 
often  with  quartz,  pyroxene,  feldspar,  axinite,  chlorite,  etc.,  in  the  Piedmontese  Alps. 

Beautiful  crystallizations  come  from  Bourg  d'Oisans,  Ala,  and  Traversella,  in  Piedmont ; 
Zermatt  and  elsewhere  in  Switzerland ;  Monzoni  in  the  Fassathal ;  the  Untersulzbachthal  and 
Zillerthal  in  the  Tyrol. 

In  N.  America,  occurs  in  Mass.,  at  Chester  ;  at  Athol ;  at  Rome.     In  Conn.,  at  Haddam. 


286  DESCRIPTIVE   MINEKALOGY. 

In  JV.  York,  at  Amity  ;  near  Monroe,  Orange  Co. ;  at  Warwick.  In  N.  Jersey ',  at  Franklin. 
In  Penn.,  at  E.  Bradford.  In  Michigan,  in  the  Lake  Superior  region.  In  Canada,  at  St. 
Joseph. 

PIEDMONTITE  (Manganepidot,  Germ.). — A  manganese  epidote  ;  formula,  H.jCatRsSieOse, 
with  R  principally  Mn  (also  Al,Fe).  Color  reddish-brown.  St.  Marcel,  Aosta  valley,  Pied- 
mont. 

ALLANITE. 

Monoclinic,  isomorphous  with  epidote.     C=  89°  V ;   O  A  14  =  122°  50J', 

i-2  A  *-2  =  63°   58' ;    c  :  1)  :  d  = 

555  0-483755  :  0-312187  :  1.      Crystals 

either  short,  flat  tabular,  or  long 
and  slender,  sometimes  acicular. 
Twins  like  those  of  epidote.  Cleav- 
age :  i-i  in  traces.  Also  massive, 
and  in  angular  or  rounded  grains. 

H.= 5-5-6.  G.= 3-0-4-2.  Lustre 
submetallic,  pitchy,  or  resinous — 
occasionally  vitreous.  Color  pitch- 
brown  to  black,  either  brownish,  greenish,  grayish,  or  yellowish.  Streak 
gray,  sometimes  slightly  greenish  'or  brownish.  Sub  translucent — opaque. 
Fracture  uneven  or  subconchoidal.  Brittle.  Double  refraction  either  dis- 
tinct, or  wanting. 

Var. — Allanite  (Cerine) .  In  tabular  crystals  or  plates.  Color  black  or  brownish-black. 
G.  =3 '50-3 '95  ;  found  among  specimens  from  East  Greenland,  brought  to  Scotland  by  C. 
Giesecke.  Bucklandite  is  anhydrous  allanite  in  small  black  crystals  from  a  mine  of  magnetite 
near  Arendal,  Norway.  Referred  here  by  v.  Rath  on  the  ground  of  the  angles  and  physical 
characters. 

Orthite.  Including,  in  its  original  use,  the  slender  or  acicular  prismatic  crystals,  often  a 
foot  long,  containing  some  water.  But  these  graduate  into  massive  forms,  and  some  orthites 
are  anhydrous,  or  as  nearly  so  as  much  of  the  allanite.  The  name  is  from  bp66s,  straight. 
The  tendency  to  alteration  and  hydration  may  be  due  to  the  slenderuess  of  the  crystals,  and 
the  consequent  great  exposure  to  the  action  of  moisture  and  the  atmosphere.  II.  =5-6. 
G.  =2 '80-3- 75.  Lustre  vitreous  to  greasy. 

Comp. — Not  altogether  certain,  as  analyses  vary  considerably,  some  showing  the  presence 
of  considerable  water.  According  to  Rammelsberg  the  Q.  ratio  for  bases  to  silicon  =  1  :  1 
(ep!ddte=l£  :  1).  Allanite  has  then  the  garnet  formula,  R3R-Si30I2,  where  R=Ce(La,Di), 
Fe(Mn),  Ca(Mg),  and  occasionally  Y,Na,,Ka,  etc.;  R^i^lorFe.  Analysis,  allanite  (Ramrn.), 
Fredrikshaab,  SiOa  33 "78,  A103  14 '03,  FeO3  6-36,  FeO  13 "63,  CeO  12-63,  LaO(DiO)  5 '67,  CaO 
12-12,  H,0  1-78=100. 

Pyr.,  etc. — Some  varieties  give  water  in  the  closed  tube.  B.B.  fuses  easily  and  swells  up 
(F.  =2*5)  to  a  dark,  blebby,  magnetic  glass.  With  the  fluxes  reacts  for  iron.  Most  varieties 
gelatinize  with  hydrochloric  acid,  but  if  previously  ignited  are  not  decomposed  by  acid. 

Obs, — Occurs  in  albitic  and  common  feldspathic  granite,  syenite,  zircon- syenite,  porphyry, 
white  limestone,  and  often  in  mines  of  magnetic  iron.  Allanite  occurs  in  Greenland  ;  at 
Criffel  in  Scotland  ;  at  Jotun  Fj  eld  in  Norway ;  at  Snarum,  near  Dresden;  near  Schmiede- 
feld  in  the  Thuringerwald.  Cerine  occurs  at  Bastnas  in  Sweden.  Orthite  occurs  at  Finbo 
and  Ytterby  in  Sweden ;  also  at  Krageroe,  etc.,  in  Norway  ;  at  Miask  in  the  Ural. 

In  Mass.,  at  the  Bolton  quarry.  In  Conn.,  at  Haddam.  In  N.  Yoi'k,  Moriah,  Essex  Co.; 
at  Monroe,  Orange  Co.  In  N.  Jersey,  at  Franklin.  In  Penn. ,  at  E.  Bradford  in  Chester  Co. ; 
at  Eastou.  Amherst  Co.,  Va.  In  Canada^  at  St.  Paul's,  C.  W. 

MUROMONTITE  and  BODENITE  from  Marienberg,  Saxony;  and  MICHAELSONITE  from 
Brevig,  are  minerals  related  to  allanite. 

ZOISITB. 

Orthorhombic.  /A  1  =  116°  40',  0  A  14  =  131°  !£' ;  c:l'.d  =  1-1493 
:  1-62125  :  1.  Crystals  lengthened  in  the  direction  of  the  vertical  axis,  and 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


287 


Corn- 


vertically  deeply  striated  or  furrowed.     Cleavage  :  i-l  very  perfect, 
monly  in  crystalline  masses  longitudinally  furrowed. 
Also  compact  massive. 

H.  =  6-6-5.  G.:=3-ll-3-3S.  Lustre  pearly  on  £-£ ; 
vitreous  on  surface  of  fracture.  Color  grayish- white, 
gray,  yellowish,  brown,  greenish-gray,  apple-green ; 
also  peach-blossom-red  to  rose-red.  Streak  uiicolored. 
Transparent  to  subtranslucent.  Double  refraction 
feeble,  optic-axial  plane  i-l ;  bisectrix  positive,  normal 
to  i-l ;  DesCl. 

Var. — A.  LiME-ZoisiTE.  1.  Ordinary.  Colors  gray  to  white 
and  brown.  2.  Rose-red,  or  Thulite.  G.  =8*124  ;  fragile;  dichro- 
ism  strong1,  especially  in  the  direction  of  the  vertical  axis  ;  in  this 
direction  reddish,  transversely  colorless ;  from  Norway,  Piedmont. 
fiaussurite,  which  forms  with  smaragdite  the  euphotide  of  the  Alps, 
is  a  lime-soda  zoisite. 

Comp. — A  lime-epidote,  with  little  or  no  iron,  and  thus  differing  from  epidote.  Q.  ratio 
as  in  epidote,  H  :  Ca=l  :  4,  and  Ca  :  B  :  Si=4  :  9  :  12,  whence  the  formula  H^Ca^sSieOae. 
Analysis,  Ramm.,  Goshen  (G.--3'341)  BiOj  40'OG,A1O3  3067,  FeO3  2'45,  CaO  23'91,  MgO 
0  49,  H-jO  2*25 =99  83.  The  amount  of  iron  sesquioxide  varies  from  0  to  6*33  p.  c.  ;  if  much 
more  is  present,  amounting  to  a  sixth  atomically  of  the  protoxide  bases,  the  compound 
appears  to  take  the  monoclinic  form  of  epidote,  instead  of  the  orthorhombic  of  zoisite. 

Pyr,,  etc, — B.B.  swells  up  and  fuses  at  3-3 "5  to  a  white  blebby  mass.  Not  decomposed  by 
acid  ;  when  previously  ignited  gelatinizes  with  hydrochloric  acid. 

Obs.— Occurs  at  Saualpe  in  Carinthia  ;  Baireuth  in  the  Fichtelgebiroje  ;  Sterzing,  Tyrol ; 
Lake  Geneva ;  Schwarzwald ;  Arendal,  etc.  In  the  United  States,  found  in  Vermont,  at 
Willsboro  and  Montpelier.  In  Mass.,  at  Goshen,  Chesterfield,  etc.  In  Penn.,  in  Chester  Co.; 
at  Unionville,  white  ( Unionite).  In  Tenn. ,  at  the  Ducktown  copper  mines. 

JADEITE  is  one  of  the  kinds  of  pale  green  stones  use  d  in  China  for  making  ornaments,  and 
passing  under  the  general  name  of  jade  or  nephrite.  Mr.  Pumpelly  remarks  that  the  feUsui 
is  perhaps  the  most  prized  of  all  stones  among  the  Chinese.  In  composition  mainly  a  silicate 
of  aluminum  and  sodium.  In  its  high  specific  gravity  like  zoisite. 

GADOLINITE.— Monoclinic  (DesCl.).  Color  greenish-black.  Contains  yttrium,  cerium,  and 
generally  beryllium  ;  though  the  last  is  sometimes  absent,  through  alteration  (DesCl.). 
Sweden  ;  Greenland  ;  Norway. 

MOSANDRITE. — A  silicate  containing  titanium,  cerium,  and  calcium.     Brevig,  Norway. 


ILVAITE.    Lievrite.     Yenite. 

Orthorhombic.    7 A 1  =112°  38',  O  A 14  =  146°  24' ;  c  :  I  :  a  =  0-66608 
1-5004: :  1.     O  A  1  =  141°  24',  O/\24=  138°  29'.    Lateral 
faces  usually  striated  longitudinally.     Cleavage :  parallel 
to  the  longer  diagonal,  indistinct.     Also  columnar  or  com- 
pact massive. 

II.  =  5 -5-6.  G.= 3*7-4-2.  Lustre  submetallic.  Color 
iron-black,  or  dark  grayish-black.  Streak  black,  inclining 
to  green  or  brown.  Opaque.  Fracture  uneven.  Brittle. 


Comp. — Q.  ratio,  for  R+R  :  Si  :  H— 9  :  8:1,  and  for  bases,  including 
hydrogen,  to  silicon  5  :  4  (Stadeler).  Sipocz  by  the  analysis  of  entirely 
unaltered  crystals  (G.  =4'037)  from  Elba  confirms  the  conclusions  of 
Stadeler  in  regard  to  the  presence  of  chemically  combined  water,  and 
adopts  the  same  formula,  viz.: — H2Ca2Fe4FeSi4Oi8.  This  requires  : 
Silica  29 '34,  iron  sesquioxide  19*56,  iron  protoxide  35  21,  lime  13*69, 
water  2 '20  =  100 ;  manganese  protoxide  is  also  sometimes  present  in  small  quantities.  Ram 
melsberg  considered  the  water  as  due  to  alteration. 


DESCRIPTIVE    MINERALOGY. 


Pyr.,  etc. — B.B.  fuses  quietly  at  2 '5  to  a  black  magnetic  bead.  With  the  fluxes  reacts  for 
iron.  Some  varieties  give  also  a  reaction  for  manganese.  Gelatinizes  with  hydrochloric  acid. 

Obs, — Found  in  Elba,  and  at  the  mine  of  Temperino  in  Tuscany.  Also  at  Fossum  and  at 
Sk'een  in  Norway  ;  in  Siberia ;  near  Andreasberg  ;  ^near  Predazzo,  Tyrol ;  at  Schneeberg ;  at 
Hebrun  in  Nassau  ;  at  Kangerdluarsuk  in  Greenland. 

Reported  as  formerly  found  at  Cumberland,  R.  I.;  also  at  Milk  Row  quarry,  Somerville, 
Mass. 

AKDKNNITE!  (Dewalquite). — Near  ilvaite  in  form.  Habit  prismatic;  vertically  striated. 
Composition  given  by  the  analyses,  Lasaulx  and  Bettendorf,  Si02  29 '60,  rArl03  23*50,  MnO 
25-88,  Fe03  l-«8,  CaO  1'81,  MgO  3 '38,  V2O5  9'20,  ign.  404=99'09.  Color  dark  rosin-brown. 
In  thin  splinters  transparent.  Other  varieties,  of  a  bright  sulphur -yellow  color  (but  opaque 
and  dull),  contain  arsenic  (9-33  p.  c.  As2O5)  instead  of  vanadium.  Between  these  two  ex- 
tremes are  a  series  of  compounds  containing  both  arsenic  and  vanadium.  Lasaulx  regards 
the  arsenic-ardennite  as  having  come  from  the  other  through  alteration.  Locality,  Ottrez  in 
the  Ardennes,  Belgium.  ROSCOELITE  (p.  345)  is  another  silicate  containing  vanadium. 


AXINITE. 


Triclinic.  Crystals  usually  broad,  and  acute-edged.  Making  m  =  0, 
P  =  'f,u  =  _I/,a  (brachyd.) :  I  (macrod.) :  c  =  0-49266  : 1 :  0-45112.  Cleav- 
age :  i-l  (v)  quite  distinct ;  in  other  directions  indistinct.  Also  massive, 
lamellar,  lamellae  often  curved  ;  sometimes  granular. 


558 


Dauphiny. 


Dauphiny, 


H.  =6-5-7.  G.=3-271,  Haidingerf  a  Cornish  specimen.  Lustre  highly 
glassy.  Color  clove-brown,  plum-blue,  and  pearl-gray;  exhibits  trichroism, 
different  colors,  as  cinnamon-brown,  violet-blue,,  olive-green,  being  seen  in 
different  directions.  Streak  -uncolored.  Transparent  to  subtranslucent. 
Fracture  conchoidal.  Brittle.  Pyroelectric,  with  two  axes,  the  analogue  (L) 
and  antilogue  (T)  poles  being  situated  as  indicated  in  f.  558  (G.  Rose). 

Comp. — Analyses  vary.  If  it  contains  2  p.  c.  water  (Ramm.),  and  if  B2  replaces  Al,  then 
it  is  a  unisilicate  with  the  formula  RvftsSieOg.?,  R=Fe,Mn,Ca,Mg,  and  K2,  while  R=B2,A1 
(B2  :  Al=l  :  2).  Analysis  (Ramm.),  Oisans,  Dauphine,  SiO2  43'46,  B2O3  5'61,  A103  16'33, 
Fe03  2-80,  FeO  6-78,  MnO  2-62,  CaO  2019.  MgO  1-73,  KaO  0-11,  H20  1-45=101-08. 

Pyr.,  etc. — B.B.  fuses  readily  with  intumescence,  imparts  a  pale  green  color  to  the  O.F., 
and  fuses  at  2  to  a  dark  green  to  black  glass ;  with  borax  in  0.  F.  gives  an  amethystine  bead 
(manganese),  which  in  R.F.  becomes  yellow  (iron).  Fused  with  a  mixture  of  potassium  bisul- 


OXYGEN   COMPOUNDS — ANHYDROUS    SILICATES. 


289 


phate  and  fluor  on  the  platinum  loop  colors  the  flame  green  (boron).  Not  decomposed  by 
acids,  but  when  previously  ignited,  gelatinizes  with  hydrochloric  acid. 

Obs. — Axinite  occurs  near  Bourg  d'Oisans  in  Dauphiny  ;  at  Santa  Maria,  Switzerland;  at 
Kongsberg  ;  in  Normark  in  Sweden  ;  in  Cornwall ;  in  Devonshire,  near  Tavistock ;  at  Phips- 
burg,  Maine  ;  at  Wales,  Maine  ;  at  Cold  Spring,  N.  Y. 

DANBURITE.— Triclinic.  CaB2Si2O8= Silica  48' 8,  boron  trioxide  28*5,  lime  22 •?= 100. 
Occurs  with  feldspar  in  imbedded  masses  of  yellow  color  in  dolomite,  at  Danbury,  Ct. 


IOLITE.     Cordierite.     Dichroite. 


561 


Orthorhombic.     In  stout  prisms  often  hexagonal.     1 1\  1=  119°  10' 
60°  50',  O  A  l-£  =150°  49'.     Cleavage  :  i-l  distinct ;  i-l 
and  O  indistinct.     Crystals  often  transversely  divided 
or  foliated  parallel  with  O.     Twins :  twinning-plane 
/.     Also  massive,  compact. 

II. =7-7-5.  G.= 2-56-2-67.  Lustre  vitreous.  Color 
various  shades  of  blue,  light  or  dark,  smoky-blue  ;  pleo- 
chroic,  being  often  deep  blue  along  the  vertical  axis, 
and  brownish-yellow  or  yellowish-gray  perpendicular  to 
it.  Streak  uncolored.  Transparent — translucent.  Frac- 
ture subconchoidal. 


and 


Comp. — Q.  ratio  for  bases  and  silicon  4  :  5  or  1  :  1£.  The  state  of  oxidation  of  the  iron  is 
still  unascertained,  and  hence  there  is  uncertainty  as  to  the  proportion  between  the  protoxides 
and  sesquioxides.  The  ratio  usually  deduced  for  R  :  R  :  Si  is  1  :  3  :  5.  The  formula  R2ft2Si5 
O)8,  which  corresponds  to  this  ratio,  =,  if  R=Mg,Fe  and  Mg  :  Fe=2  :  1,  Silica  49'4, 
alumina  33 '9,  magnesia  8 '8,  iron  protoxide  7 '9  =  100. 

Pyr.,  etc. — B.B.  loses  transparency  and  fuses  at  5-5 '5.  Only  partially  decomposed  by 
acids.  Decomposed  on  fusion  with  alkaline  carbonates. 

Obs. — lolite  occurs  in  granite,  gneiss,  hornblendic,  chlorite  and  hydro-mica  schist,  and  allied 
rocks,  with  quartz,  orthoclase  or  albite,  tourmaline,  hornblende,  andalusite,  and  sometimes 
beryl.  Also  rarely  in  volcanic  rocks.  Occurs  at  Bodenmais,  Bavaria  ;  at  Ujordlersoak  in 
Greenland  ;  at  Krageroe  in  Norway  ;  Tunaberg  in  Sweden  ;  Lake  Laach.  At  Haddam,  Conn.; 
at  Brimfield,  Mass.;  also  at  Richmond,  N.  H. 

Alt. — The  alteration  of  iolite  takes  place  so  readily  by  ordinary  exposure,  that  the  mineral 
is  most  commonly  found  in  an  altered  state,  or  enclosed  in  the  altered  iolite.  For  the  dis- 
tinguishing characters  of  the  different  kinds  of  altered  iolite,  see  FINITE,  FAHLUNITE, 
etc.,  under  HYDROUS  SILICATES. 


Mica  Group. 

The  minerals  of  the  Mica  group  are  alike  in  having  (I)  the  prismatic 
angle  120°  ;  (2)  eminently  perfect  basal  cleavage,  affording  readily  very 
thin,  tough  laminae ;  (3)  potash  almost  invariably  among  the  protoxide 
bases  and  alumina  among  the  sesquioxide ;  (4)  the  crystallization  approxi- 
mately either  hexagonal  or  orthorhombic.  and  therefore  the  optic  axis,  or 
optic-axial  plane,  at  right  angles  (or  nearly  so)  to  the  cleavage  surface. 

Sodium  is  sparingly  present  in  some  micas,  and  is  characteristic  of  the  hydrous  species 
paragonite  (p.  332).  Lithium,  rubidium,  and  caesium  occur  in  lepidolite,  and  lithium  in  some 
biotite.  Fluorine  is  often  present,  probably  replacing  oxygen.  Titanium  is  found  sparingly 
in  several  kinds,  and  is  a  prominent  ingredient  of  one  species,  astrophyllite.  It  is  usually 
regarded  as  in  the  state  of  titanium  dioxide  replacing  silica ;  but  it  is  here  made  basic, 

19 


290 


DESCRIPTIVE   MINEKALOGY. 


The  species  of  the  Mica  group  graduate  into  the  hydrous  micas  of  the  Margarodite  group 
(p.  331) ;  and  through  these  they  also  approach  the  foliated  species  of  the  Talc  and  Chlorite 
groups,  especially  the  latter. 

PHLOGOPITE. 

Orthorhombic.      7A/=120°,   and   habit   hexagonal.      Prisms   usually 
oblong  six-sided  prisms,  more  or  less  tapering,  with  irregular 
562          sides ;    rarely,  when   small,  with   polished   lateral   planes. 
Cleavage  basal,  highly  eminent.     Not  known  in  compact 
massive  forms. 

H.=2-5-3.  Gr.  =  2-78-2-S5.  Lustre  pearly,  often  sub- 
metallic,  on  cleavage  surface.  Color  yellowish- brown  to 
brownish-red,  with  often  something  of  a  copper-like  reflec- 
tion;  also  pale  brownish-yellow,  green,  white,  colorless. 
Transparent  to  translucent  in  thin  folia.  Thin  laminae 
tough  and  elastic.  Optical-axial  divergence  3°-20°,  rarely 
less  than  5°. 

Oomp. — The  bases  include  magnesium  and  little  or  no  iron.  Q.  ratio 
R  :  Si=l  :  1.  Formula  probably  (Ramm.)  K2Mg6AlSi5020  — Silica  4073, 
alumina  13-93,  magnesia  32'57,  potash  12 '77=100. 

Pyr.,  etc. — In  the  closed  tube  gives  a  little  water.  Some  varieties 
give  the  reaction  for  fluorine  in  the  open  tube,  while  most  give  little  or 
no  reaction  for  iron  with  the  fluxes.  B.  B.  whitens  and  fuses  on  the  thin 
edges.  Completely  decomposed  by  sulphuric  acid,  leaving  the  silica  in 
thin  scales. 

Obs. — Phlogopite  is  especially  characteristic  of  serpentine  and  crystalline  limestone  or 
dolomite. 

Occurs  in  limestone  in  the  Vosges.  Includes  probably  the  mica  found  in  limestone  at  Alt- 
Kemnitz,  near  Hirschberg  ;  that  of  Baritti,  Brazil,  of  a  golden-yellow  color,  having  the  optical 
angle  5°  30'  and  parallel  to  the  shorter  diagonal  (Grailich) ;  and  a  brown  mica  from  limestone 
of  Upper  Hungary,  affording  Grailich  the  angle  4°-5°. 

Occurs  in  New  York,  at  Gouverneur ;  at  Pope's  Mills,  St.  Lawrence  Co.  ;  at  Edwards ; 
Warwick;  Natural  Bridge  ;  at  Sterling  Mine,  Morris  Co.,  N.  J.  ;  Newton,  N.  J.;  at  St.  Je- 
rome, Canada  ;  at  Burgess,  Canada  West. 

ASPIDOLITE  (v.  Kobell). — Approaches  in  composition  a  soda-phlogopite.  Green.  Foliated. 
Zillerthal,  Tyrol. 

MANGANOPHYLLITE. — Q.  ratio  for  R  :  R  :  Si=3  :  1  :  4  (nearly).  Foliated  like  the  micas. 
Color  bronze-red.  Analysis,  Igelstrom,  SiO2  38-50,  A103  ll'OO,  FeO  3 '78,  MnO  21'40,  CaO 
3-20,  MgO  15-01,  K2O(Na20)  5'51,  ign.  1-60=100.  Paisberg,  Sweden. 

BIOTITB. 

Hexagonal  (V).  R  A  R  —  62°  57'  (crystals  f r.  Vesuvius,  Hessenberg) ;  c  = 
4-911126.  Habit  often  rnonoclinic.  Prisms  commonly  tabular.  Cleavage  : 

basal  highly  eminent.  Often  in  disseminated 
.scales,  sometimes  in  massive  aggregations  of 
cleavable  scales. 

H.=2-5-3.  G.=2-7-3-l.  Lustre  splendent, 
and  more  or  less  pearly  on  a  cleavage  surface, 
and  sometimes  submetallic  when  black ;  lateral 
surfaces  vitreous  when  smooth  and  shining. 
Colors  usually  green  to  black,  often  deep  black 
in  thick  crystals,  and  sometimes  even  in  thin 
laminae,  unless  the  laminae  are  very  thin  ;  such 
thin  laminae  green,  blood-red,  or  brown  by  transmitted  light ;  rarely  white. 


OXYGEN   COMPOUNDS — ANHYDROUS    SILICATES.  291 

Streak  tmcolored.  Transparent  to  opaque.  Optically  uniaxial.  Some- 
times biaxial  with  slight  axial  divergence,  from  exceptional  irregularities, 
but  the  angle  not  exceeding  5°  and  seldom  1°. 

Comp.,  Var. — Biotite  is  a  magnesia-iron  mica,  part  of  the  aluminum  (Al)  being  replaced 
by  iron  (Fe),  and  Fe  and  Me  existing  among  the  protoxide  bases.  Black  is  the  prevailing  color, 
but  brown  to  white  also  occur.  The  results  of  analyses  vary  much,  and  for  the  reason  already 
stated — the  non-determination,  in  most  cases,  of  the  degree  of  oxidation  of  the  iron. ;  and 
the  exact  atomic  ratio  for  the  species  and  it's  limits  of  variation  are  therefore  not  precisely 
understood.  The  Q.  ratio  of  bases  to  silicon  is  generally  1:1,  that  is  the  formula  in  general 
R,Si04,  where  R=K,(Na.,Li2)Fe,Mg(Ca),  or  Al,Fe(3R=ft). 

Analyses  :  1,  Bally  ellin  ;  2,  Vesuvius  ;  3,  Portland,  Conn. : 

SiO2  A1O3  FeO3  FeO  CaO            MgO  K20  NaaO    Li2O  ign 

(1)  35-55  17-08  23-70  5'50  3"68  9-45  0'35     4'30=99'61,  Haughton. 

(2)  40-91  17-79  3-00  7 '03  0'30           19 '04  9  -96 =98-03,  Chodnew. 

(3)135-61  20-03  0-13  21 '85  119MnO    5'23  9-69  0-52      0'93  1-87,  F  0'76,  TiO2  1"46, 

Cltr.=99'27,  Hawes. 

The  above  analyses  give  the  ratio  of  unisilicates,  when  the  water  is  neglected ;  in  others 
the  ratio  of  1  :  1  is  obtained  only  when  the  water  is  brought  into  account. 

Pyr.,  etc. — Same  as  phlogopite,  but  with  the  fluxes  it  gives  strong  reactions  for  iron. 

ObS; — A  common  constituent  of  many  volcanic  rocks.  Fine  specimens  obtained  at  Vesu- 
vius ;  L.  Baikal ;  Zillerthal ;  Pargas  ;  Miask  ;  Sala.  Also  from  Greenwood  Furnace,  N.  Y. ; 
Moriah,  N.  Y.  ;  Easton,  Penn.  ;  Topsham,  Me.,  etc. 

The  biotite  of  Vesuvius,  according  to  the  optical  examination  of  Hintze,  is  monocUnic. 
(See  also  Tscherrnak,  Min.  Mitth.,  1876.  187.) 


LEPLDOMELANE. 

Hexagonal  (?).  In  small  six-sided  tables,  or  an  aggregate  of  minute  scales. 
Cleavage :  basal,  eminent,  as  in  other  micas. 

H.  =  3.  G.  =  3*0.  Lustre  adamantine,  inclining  to  vitreous,  pearly. 
Color  black,  with  occasionally  a  leek-green  reflection.  Streak  grayish- 
green.  Opaque,  or  translucent  in  very  thin  laminae.  Somewhat  brittle,  or 
but  little  elastic.  Optically  uniaxial ;  or  biaxial  with  a  very  small  axial 
angle. 

* 

Gomp. — An  iron-potash  mica.  Q.  ratio  for  bases  and  silicon  1:1;  for  R  :  R,  mostly  1  :  3, 
but  varying  to  1  to  more  than  3  ;  of  doubtful  limits,  on  account  of  the  doubts  as  to  the  state 
of  the  iron  in  most  of  the  analyses.  Differs  from  biotite  in  the  smaller  proportion  of  prot- 
oxides and  little  Al  and  Mg,  but  appears  to  agree  with  it  in  optical  characters. 

Pyr.,  etc. — B.B.  at  a  red  heat  becomes  brown  and  fuses  to  a  black  magnetic  globule. 
Easily  decomposed  by  hydrochloric  acid,  depositing  silica  in  scales.  Analysis,  Cooke,  Rock- 
port,  Mass.,  SiO.2  39-91,  A103  1673,  FeO3  12'07,  FeO  17-48,  MnO  0-54,  MgO  0-62,  K,0  10'66, 
Na2O(Li,O)  0-59,  H,O  1-50,  F0'45  =  100. 

Obs. — Occurs  at  Persberg  in  Wermland,  Sweden  ;  at  Abborf orss  in  Finland ;  in  Ireland,  in 
Donegal  and  Leinster  Cos.  ;  at  Ballyellin,  etc.  From  Cape  Ann,  Mass.  (Annite). 

ASTROPHYLLITE. — Usually  in  tabular  prisms.  Color  bronze-yellow.  Analysis,  Pisani,  SiO2 
33-22,  TiO>  7-66,  A1O3  4"32,  Fe03  4 '05,  FeO  25 '48,  MnO  10  "70,  MgO  1'37,  CaO  1'22,  Na2O 
2-71,  K2O  6-29,  H,O  2 '01  =99 '03.  Brevig,  Norway  ;  El  Paso  County,  Colorado. 


MUSCOVITE.     Kaliglimmer,  Germ. 

Monoclinic  (Tscherrnak).  If\I  =120°.  Cleavage:  basal  eminent; 
occasionally  also  separating  in  fibres  parallel  to  a  diagonal.  Twins  :  often 
observable  by  internal  markings,  or  by  polarized  light ;  composition  parallel 


292  DESCRIPTIVE   MINERALOGY. 

to  /consisting  of  six  individuals  thus  united  ;  sometimes  a  union  of  I  to 
i-L  Folia  often  aggregated  in  stellate,  plumose,  or  globular  forms ;  or  in 
scales,  and  scaly  massive. 

564  565  566 


Miask,  Ural.  Binnenthal. 

H. =2-2*5.  G.=2*75-3'l.  Lustre  more  or  less  pearly.  Color  white, 
gray,  brown,  hair-brown,  pale  green,  and  violet,  yellow,  dark  olive-green, 
rarely  rose-red ;  often  different  for  transmitted  and  reflected  light,  and  dif- 
ferent also  in  vertical  and  transverse  directions.  Streak  un colored.  Trans- 
parent to  translucent.  Thin  laminae  flexible  and  elastic,  very  tough.  Double 
refraction  strong ;  optic-axial  angle  4r4°-78°  ;  the  axial  plane  makes  an  angle 
of  88°  20'  (Tschermak)  with  the  base. 

Oomp — The  quantivalent  ratio  for  bases  arid  silicon  is  generally  4  :  5  (1  :  1J),  rarely  3  :  4, 
etc.  Water  is  generally  present,  sometimes  as  much  as  5  p.  c.;  and  the  kinds  containing 
from  3  to  5  p.  c.  water  have  been  referred  to  the  species  margarodite  (p.  331).  If  the 

i 
water  is  regarded  as  chemically  combined,  that  id,  as  basic,  the  Q.  ratio  for  R  :  ft  :  Si  is  then 

— 1  :  3  :  4  (R  :  Si— 1  :  1),  also  1:6:8,  1:2:4,  1:3:5,  etc.  R  here  is  potassium  (K) 
mostly,  but  also  hydrogen  (H).  ft— aluminum  mostly,  also  iron.  Fluorine  is  often  present, 
but  at  most  not  more  than  about  1  p.  c.  Analysis,  Smith  and  Brush,  Monroe,  Ct.,  SiO2  46 '50, 
A103  33-91.  FeO3  2'69,  MgO  0'90  Na2O  2 -70,  K,O  7*32,  H2O  4'68,  F  0'82,  01  0'31=99'78. 

Pyr.,  etc. — In  the  closed  tube  gives  water,  which  with  brazil-wood  often  reacts  for  fluorine. 
B.B.  whitens  and  fuses  on  the  thin  edges  (F.  =5 '7,  v.  Kobell)  to  a  gray  or  yejlow  glass.  With 
fluxes  gives  reactions  for  iron  and  sometimes  manganese,  rarely  chromium.  Not  decomposed 
by  acids.  Decomposed  on  fusion  with  alkaline  carbonates. 

Obs. — Muscovite  is  the  most  common  of  the  micas.  It  is  one  of  the  constituents  of  granite, 
gneiss,  mica  schist,  and  other  related  rocks,  and  is  occasionally  met  with  in  granular  lime- 
stone, trachyte,  basalt,  iava ;  and  occurs  also  disseminated  sparingly  in  many  fragmental 
rocks.  Coarse  lamellar  aggregations  often  form  the  matrix  of  topaz,  tourmaline,  and  other 
mineral  species  in  granitic  veins. 

Siberia  affords  laminee  of  mica  sometimes  exceeding  a  yard  in  diameter  ;  and  other  remark- 
able foreign  localities  are  Finbo  in  Sweden,  and  Skutterud  in  Norway.  Faclmie  or  chromium 
mica  occurs  at  Greiner  in  the  Zillerthal,  at  Passeyr  in  the  Tyrol,  and  on  the  Dorfner  Alp,  as 
well  as  at  Schwarzenstein. 

In  N.  Hamp.,  at  Acworth,  Grafton,  etc.,  in  granite,  the  plates  at  times  a  yard  across  and 
perfectly  transparent.  In  Maine,  at  Paris  ;  at  Buckfield.  In  Mass. ,  at  Chesterfield  ;  at  Goshen. 
In  Conn.,  in  Portland  ;  near  Middletown.  In  N.  York,  near  Warwick;  Edenville  ;  in  the 
town  of  Edwards.  In  Perm.,  at  Pennsbury;  at  Unionville  ;  Delaware  Co.,  at  Middletown. 
In  Maryland,  at  Jones's  Falls.  In  western  North  Carolina,  where  it  is  mined. 


LEPIDOLITE.     Lithia  Mica.     Lithionglimmer,  Germ. 

Orthorhombic.     /A  /  =  120°.     Forms  like  those  of  muscovite.     Cleav- 
age :  basal,  highly  eminent.     Also  massive  scaly-granular,  coarse  or  tine. 
H.=2-5-4.     GK =2*84-3.     Lustre  pearly.     Color  rose-red,  violet-gray,  or 


OXYGEN   COMPOUNDS. ANHYDROUS    SILICATES. 


293 


lilac,  yellowish,   grayish-white,   white.      Translucent.      Optic-axial   angle 

70°-78°     sometimes  45°-GO°. 


Comp.  —  Q.  ratio  for  bases  and  silicon  mostly  1  :  l£  ;  and  for  R  :  R  :  Si=l  :  3  :  6,  or  1  :  4 

:  8  ;  the  formula  in  the  latter  case  is  R-6Al4Sii2O39.  R  includes  potassium,  also  lithium, 
rubidium,  and  coesium  ;  and,  in  the  Zinnwald  mica,  thallium  has  been  detected.  Fluorine  is 
present,  and  the  ratio  to  oxygen  mostly  1  :  12.  Analysis,  Reuter,  from  Rozena,  SiO2  50  "43, 
A1O3  28-07,  MnOs  0'88,  MgO  1'42,  K,O  10*59,  Na-2O  1-46,  Li,O  1'23,  F  4'86=98'94. 

Pyr.,  etc.  —  In  the  closed  tube  gives  water  and  reaction  for  fluorine.  B.B.  fuses  with  in- 
tumescence at  2-2  '5  to  a  white  or  grayish  glass,  sometimes  magnetic,  coloring  the  flame 
purplish-red  at  the  moment  of  fusion  (lithia).  With  the  fluxes  some  varieties  give  reactions 
for  iron  and  manganese.  Attacked  but  not  completely  decomposed  by  acids.  After  fusion, 
gelatinizes  with  hydrochloric  acid. 

Obs.  —  Occurs  in  granite  and  gneiss,  especially  in  granitic  veins,  and  is  associated  some- 
times with  cassiterite,  red,  green,  or  black  tourmaline,  amblygonite,  etc.  Found  near  Uto 
in  Sweden  ;  at  Zinnwald  in  Bohemia  ;  Penig,  etc.  in  Saxony  ;  in  the  Ural  ;  at  Rozena  in 
Moravia  ;  on  Elba  ;  at  St.  Michael's  Mount  in  Cornwall.  In  the  United  States,  at  Paris  and 
Hebron,  Me.  ;  near  Middletown,  Conn. 

Named  lepidolite  from  Ae/r/f,  scale,  after  the  earlier  German  name  8c?iuppenstem,  alluding 
to  the  scaly  structure  of  the  massive  variety  of  Rozena. 

CKYOPHYLLITE  (Cooke)  —  Q.  ratio  R  :  R  :  Si=:3  :  4  :  14,  with  R—  Fe,K2,Li2(Na,Rb,Cs,)2 
and  ft=Al.  Orthorhombic.  In  scales  like  the  micas.  Color  by  transmitted  light  emerald- 
green.  Cape  Ann,  Mass. 


Scapolite    Group. 

In  the  species  of  the  Scapolite  group,  the  quantivalent  ratio  varies  from 
1  :  1  :  2,  1  :  2  :  3,  1  :  3  :  4,  to  1  :  2  :  4  and  1  :  2  :  6|,  but  the  species  are 
closely  alike  in  the  square-prismatic  forms  of  their  crystals,  in  the  small 
number  and  the  kinds  of  occurring  planes,  and  in  their  angles.  The  species 
are  white,  or  grayish-white,  in  color,  except  when  impure,  and  then  rarely 
of  dark  color  ;  the  hardness  5-6'5.  G.  =  2-5-2-8.  The  alkali-metal  present, 
when  any,  is  sodium,  with  only  traces  of  potassium.  An  increase  in  the 
amount  of  alkali  is  accompanied  by  an  increase  in  the  silica. 


MEIONITE. 

Tetragonal:   O  M-i  =  156°  18';  c  =  0-439.     Sometimes  hemihedral  in 
the  planes  3-3,  the  alternate  being  wanting.     Cleavage  :  i-i 
and  /  rather  perfect,  but  often  interrupted. 

H.=5-5-6.  G.  =  2-6-2-74.  Lustre  vitreous.  Colorless 
to  white.  Transparent  to  translucent ;  often  much  cracked 
within. 


Comp.— Q.  ratio  f or  R  :  R  :  Si=l  :  2  :  3  ;  formula  R6R4Si9O36.  If  R= 
Ca  :  Na2  =  10  :  1,  and  R=A1 ;  this  is  equivalent  to  Silica  41/6,  alumina 
31 '7,  lime  24 '1,  soda  2 '6  =  100.  Neminar  has  found  that  meionite  loses 
1  p.  c.  water  at  a  very  high  temperature,  so  that  R  must  be  also  replaced 
by  H2  ;  his  analysis  gives  approximately  the  ratio  1  :  2  :  3. 

Pyr.,  etc. — B.B.  fuses  with  intumescence  at  3  to  a  white  blebby  glass. 
Decomposed  by  acid  without  gelatinizing  (v.  Rath). 

Obs. — Occurs  in  small  crystals  in  geodes,  usually  in  limestone  blocks,  on  Monte 
near  Naples. 


294: 


DESCRIPTIVE   MINERALOGY. 


WERNERITE,     Scapolite. 

Tetragonal:  O  A l-i  =  156°  14J-' ;  c  =  0-4398.  Often  hemihedral  in 
planes  3-3  and  a-2  (p.  30).  Cleavage :  i-i  and  /  rather 
distinct,  but  interrupted.  Also  massive,  granular,  or 
with  a  faint  fibrous  appearance  ;  sometimes  columnar. 
II.  =  5-6.  G-.  =  2-63-2-8.  Lustre  vitreous  to  pearly 
externally,  inclining  to  resinous ;  cleavage  and  cross- 
fracture  surface  vitreous.  Color  white,  gray,  bluish, 
greenish,  and  reddish,  usually  light.  Streak  uncolored. 
Transparent — faintly  subtranslucent.  Fracture  sub- 
con  choidal.  Brittle. 


Comp.— Q,  ratio  for  R  :  R  :  Si=l  :  3  :  4  (R+R  :  Si=l  :  1) ; 

formula  RRSi.2O8=Ca(JsTa,)AlSi2O,.  Analysis,  v.  Rath.  Pargas,  SiO2  45  -46,  A1O3  30'90,  CaO 
17-22,  Na2O  2-29,  K2O  1'31,  H2O  1-29=98 '53.  Some  varieties  vary  widely  from  the  above 
ratio. 

Pyr,,  etc.— B.B.  fuses  easily  with  intumescence  to  a  white  blebby  glass.  Imperfectly  de- 
composed by  hydrochloric  acid. 

Diff- — Recognized  by  its  square  form  ;  resembles  feldspar  when  massive,  but  has  a  charac- 
teristic fibrous  appearance  on  the  cleavage  surface  ;  it  is  also  more  fusible,  and  has  a  higher 
specific  gravity. 

Obs. — Occurs  in  metamorphic  rocks ;  sometimes  in  beds  of  magnetite  accompanying  lime- 
stone. Some  localities  are  :  Arendal,  Norway ;  Wermland  ;  Pargas,  Finland  ;  L.  Baikal,  etc. 
In  the  following  those  of  ths  wernerite  and  ekebergite  are  not  yet  distinguished.  In  MOM., 
at  Bolton ;  Westfield.  In  Conn. ,  at  Monroe.  In  N.  York,  in  Warwick  ;  in  Orange  and 
Essex  Co. ,  etc.  In  N.  Jersey,  at  Franklin  and  Newton.  In  Canada,  at  G.  Calurnet  Id.  ; 
at  Hunterstown ;  Grenville. 

The  following  are  other  members  of  the  scapolite  group  : 

SARCOLITE.— Q.  ratio  for  R  :  R  :  Si=l  :  1  :  2.  In  minute  flesh-red  crystals  at  Mt. 
Somma. 

PARANTHITE. — Q.  ratio=l  :  3  :  4.  EKEBERGITE.  Q.  ratio=l  :  2  :  4|,  containing  6-8  p. 
c.  soda.  MIZZONITE.  Q.  ratio=l  :  2  :  5£,  containing  lOp.  c.  soda.  In  crystals  at  Mt.  Sornma, 
DIPYRE.  Q.  ratio=l  :  2  :  6,  and  for  Ca  :  Na2=l  :  1.  MARIALITE.  Q.  ratio=l  :  2  :  6,  and 
for  Ca  :  Na2=l  :  2. 


Nephelite    Group. 

NEPHELITB.     Nepheline. 


Hexagonal. 
569 


and 


135°  55'  ;  G  —  0-839.  Usual  forms  six-sided 
twelve-sided  prisms  with  plane  or  modified  sum- 
mits. Fig.  569,  summit  planes  of  a  crystal.  Cleav- 
age :  ./distinct,  O  imperfect.  Also  massive,  com- 
pact ;  also  thin  columnar. 

II:  =5  -5-6.  G.  =  2.5-2-65.  Lustre  vitreous- 
greasy  ;  a  little  opalescent  in  some  varieties.  Color- 
less, white,  or  yellowish  ;  also  when  massive,  dark- 
green,  greenish  or  bluish-gray,  brownish  and  brick- 
red.  "Transparent  —  opaque.  Fracture  subcon- 
choidal.  Double  refraction  feeble  ;  axis  negative. 

Var.  —  1.    Glassy,  or  Sommite.     Usually  in  small  crystals  or 
grains,  with  vitreous  lustre,  first  found  on  Mt.  Somma,  in  the 
region  of    Vesuvius.      Davyne  and  cawlinite    belong    here. 
2.  Elceolile.    In  large  coarse  crystals,  or  massive,  with  a  greasy  lustre. 


Vesuvius. 


OXYGEN   COMPOUNDS. ANHYDROUS    SILICATES.  295 

Comp. — Somewhat  uncertain,  as  all  analyses  give  a  little  excess  of  silica  beyond  what  is 
required  for  a  unisilicate.  Assuming  that  nephelite  is  a  true  unisilicate,  the  Q.  ratio  for 
i 

R  :  R  :  Si=l  :  3  :  4,  and  the  formula  is  (Na,K)2A-lSi2Os  (Ramm. );  some  of  the  Na2  being 
replaced  by  Ca.  Analysis,  Scheerer,  Vesuvius,  SiO2  44'03,  A-1O3  33 '28,  Fe03  (MnO8)  0'65, 
CaO  177,  Na2O  15'44,  K2O  4-94,  H2O  0-2 1  =  100 -32.  The  variety  Elceolite  has  the  same 
composition. 

Pyr.,  etc. — B.B.  fuses  quietly  at  3 '5  to  a  colorless  glass.     Gelatinizes  with  acids. 

Diff, — Distinguished  by  its  gelatinizing  with  acids  from  scapolite  and  feldspar,  as  also  from 
apatite,  from  which  it  differs  too  in  its  greater  hardness.  Massive  varieties  have  a  character- 
istic greasy  lustre. 

Obs, — Nephelite  occurs  both  in  ancient  and  modern  volcanic  rocks,  and  also  metamorphic 
rocks  allied  to  granite  and  gneiss,  the  former  mostly  in  glassy  crystals  or  grains  (sommite),  the 
latter  massive  or  in  stout  crystals  (dceolite) .  Nephelite  occurs  in  crystals  in  the  older  lavas  of 
Somma ;  at  Capo  di  Bove,  near  Rome ;  in  doleryte  of  Katzenbuckel,  near  Heidelberg,  etc. 
Elgeolite  is  found  in  Norway  ;  in  the  Ilmen  Mts.  ;  Urals ;  at  Litchfield,  Me.  ;  in  the  Ozark 
Mts. ,  Arkansas. 

Named  nepheline  by  Haiiy  (1801),  from  v£0e/,i?,  a  cloud,  in  allusion  to  its  becoming  cloudy  when 
immersed  in  strong  acid ;  elceolite  (by  Klaproth),  from  e/uwoj;,  02,7,  in  allusion  to  its  greasy  lustre. 

GIESECKITE  is  shown  by  Blum  to  be  a  pseudomorph  after  this  species  (see  p.  330). 

CANCKINITE. — Hexagonal,  and  in  six-  and  twelve-sided  prisms,  sometimes  with  basal  edges 
replaced;  also  thin  columnar  and  massive.  H.  =5-6.  G.  =2'42-2'5.  Color  white,  gray, 
yellow,  green,  blue,  reddish ;  streak  uncolored.  Lustre  subvitreous,  or  a  little  pearly  or 
greasy.  Transparent  to  translucent. 

COMP.— Same  as  for  nephelite,  with  some  RC03  and  water.  Analysis,  Whitney,  Litchfield, 
Me.,  SiO,  37-42,  A103  27'70,  CaO  3*91,  Na2O  20'98,  K.O  0'67,  CO2  5 '95.  H20  2'82,  Fe03 
(MnO3)  0-86  =  100-31. 

PYK.  ,  ETC.— In  the  closed  tube  gives  water.  B.B.  loses  color,  and  fuses  (F.=2)  with  intu- 
mescence to  a  white  blebby  glass,  the  very  easy  fusibility  distinguishing  it  readily  from 
nephelite.  Effervesces  with  hydrochloric  acid,  and  forms  a  jelly  on  heating,  but  not  before. 

OBS. — Found  at  Miask  in  the  Urals;  at  Barkevig,  Norway;  at  Ditro  in  Transylvania 
(ditroyte)  ;  at  Litchfield,  Me. 


4 

SODALITB. 

Isometric.  In  dodecahedrons.  Cleavage :  dodecahedral,  more  oY  less 
distinct.  Twins  :  see  f.  272,  p.  93.  AW  massive. 

H.  =  5'5-6.  G.  — 2- 136-2-401.  Lustre  vitreous,  sometimes  inclining  to 
greasy.  Color  gray,  greenish,  yellowish,  white  ;  sometimes  blue,  lavender- 
blue,  light  red.  Subtransparent — translucent.  Streak  uncolored.  Frac- 
ture conchoidal — uneven. 

,  Comp.— 3Na2A-lSi,0 8+ 2NaCl= Silica 371,  alumina 31 '71,  soda25'55,  chlorine  7 '31 =101 '65. 
Some  varieties  contain  considerably  less  chlorine. 

Pyr.,  etc. — In  the  closed  tube  the  blue  varieties  become  white  and  opaque.  B.B.  fuses 
with  intumescence,  at  3  "5-4,  to  a  colorless  glass.  Decomposed  by  hydrochloric  acid,  with 
separation  of  gelatinous  silica. 

Obs. — Occurs  in  mica  slate,  granite,  syenite,  trap,  basalt,  and  volcanic  rocks,  and  is  often 
associated  with  nephelite  (or  elaaolite)  and  eudialyte.  Found  in  West  Greenland  ;  on  Monte 
Somma;  in  Sicily;  at  Miask,  in  the  Ural;  near  Brevig,  Norway.  A  blue  variety  occurs 
at  Litchfield,  Me.,  and  at  Salem,  Mass. 

MICROSOMMITE. — Occurs  in  very  minute  hexagonal  crystals  in  masses  of  leucitic  lava 
ejected  from  Mt.  Somma.  Composition  :  a  unisilicate  of  potassium,  calcium,  and  aluminum, 
with  small  quantities  of  sodium  chloride  and  calcium  sulphate. 


296  DESCRIPTIVE   MINERALOGY. 


HAUYNITE. 

Isometric.  In  dodecahedrons,  octahedrons,  etc.  Cleavage :  dodecahe- 
dral  distinct.  Commonly  in  rounded  grains  often  looking  like  crystals 
with  a  fused  surface. 

H.=5'5-6.  G.  =  2'4-2'5.  Lustre  vitreous,  to  somewhat  gre.asy.  Color 
bright  blue,  sky-blue,  greenish-blue ;  asparagus-green.  Streak  slightly 
bluish  to  colorless.  Subtranspareut  to  translucent.  Fracture  flat  conchoi- 
dal  to  uneven. 

Comp, — 2N"a2(Ca)A:lSi208+CaSO4 ;  if  in  the  silicate  Na2  is  replaced  by  Ca,  the  atomic 
ratio  here  being  5:1,  this  gives  Silica  84  '1,3,  alumina  29 '18,  lime  10 '62,  soda  14-09,  sulphur 
trioxide  =  100.  A  little  potassium  is  also  often  present. 

Pyr.,  etc. — In  the  closed  tube  retains  its  color.  B.  B.  in  the  forceps  fuses  at  4'5  to  a  white 
glass.  Fused  with  soda  on  charcoal  affords  a  sulphide,  which  blackens  silver.  Decomposed 
by  hydrochloric  acid  with  separation  of  gelatinous  silica. 

Obs. — Occurs  in  the  Vesuvian  lavas,  on  Somma ;  in  the  lavas  of  the  Campagna,  Rome ;  in 
basalt  at  Niedermendig  and  Mayen,  L.  Laach,  etc. 

NOSITE  (Nosean).— A  8oda-ha.uyin.te ;  2Na2AlSi2O8  +  Na.>SO4,  with  also  a  little  calcium. 
Isometric ;  often  granular  massive.  Common  as  a  microscopic  ingredient  of  most  phonolytes. 
Lake  Laach,  etc. 

LAPIS-LAZULI  (Lasurstein,  Germ.). — Not  a  homogeneous  mineral  according  to  Fischer  and 
Vogelsang.  The  latter  calls  it  u  a  mixture  of  granular  calcite,  ekebergite,  and  an  isometric, 
ultramarine  mineral,  generally  blue  or  violet."  Much  used  as  an  ornamental  stone. 


LEUCITE. 

Tetragonal,  according   to   v.  Rath,     c  =  0-52637.     Usual   form    as   in 
f.  570,  closely  resembling  a  trapezohedron.     Twins  : 
570  twinning-plane  2-a  ;  crystals  often  very  complex,  con- 

sisting of  twinned  lamellae,  as  indicated  by  the  stria- 
tions  on  the  planes.  Often  disseminated  in  grains ; 
rarely  massive  granular. 

H.=5-5-6.  G.=2-44:-2-56.  Lustre  vitreous.  Color 
white,  ash-gray  or  smoke-gray.  Streak  uncolored. 
Translucent — opaque.  Fracture  conchoidal.  Brittle. 
Optically  uniaxial ;  double  refraction  weak,  negative 
(from  Aquacetosa),  positive  (from  Frascati). 

Comp Formula  K2AlSi4Oi2= Silica  55 '0,  alumina  23 '5,  potash 

21-53=100.  Q.  ratio  for  K  :  Al  :  Si=l  :  3  :  .8,  for  bases  to  silicon  1  :  2. 

Pyr.,  etc. — B.B.  infusible  ;  with  cobalt  solution  gives  a  blue  color  (alumina).  Decomposed 
by  hydrochloric  acid  without  gelatinization. 

Diff. — Distinguished  from  analcite  by  its  infusibility  and  greater  hardness. 

Obs. — Leucite  is  confined  to  volcanic  rocks,  and  is  common  in  those  of  certain  parts  of 
Europe  ;  also  found  in  those  of  the  western  United  States.  At  Vesuvius  and  some  other 
parts  of  Italy  it  is  thickly  disseminated  through  the  lava  in  grains.  It  is  a  constituent  in  the 
nephelin-doleryte  of  Merches  in  the  Vogelsberg  ;  abundant  in  trachyte  between  Lake  Laach 
and  Andernach,  on  the  Rhine. 

The  question  as  to  whether  the  crystals  of  leucite  belong  to  the  isometric  or  the  tetragonal 
system  has  excited  much  discussion.  Hirschwald  (Tsch.  Min  Mitth.,  1875,  227)  shows  that 
while  implanted  crystals  are  sometimes  distinctly  tetragonal,  others,  especially  those  which 
are  imbedded,  are  as  clearly  isometric,  while  between  the  two  there  exist  many  transition 
cases.  He  claims  that  the  mineral  is  in  fact  isometric,  but  having  a  polysymmetric  develop- 
ment, there  existing  a  wide  variation  from  the  isometric  type.  The  question  cannot  be  con- 
sidered as  entirely  decided. 


OXYGEN   COMPOUNDS. — ANHYDROUS    SILICATES.  297 


Feldspar   Group. 

The  feldspars  are  characterized  by  specific  gravity  below  2'85  ;  hardness 
6  to  7  ;  fusibility  3  to  5  ;•  oblique  or  clinohedral  crystallization  ;  prismatic 
angle  near  120°  ;  two  easy  cleavages,  one  basal,  the  other  brachydiagonal, 
inclined  together  either  90°,  or  very  near  90°  ;  cleavage  a  prominent  fea- 
ture of  many  massive  kinds,  and  distinct  in  the  grains  of  granular  varieties, 
giving  them  angular  forms  ;  close  isomorphism,  and  a  general  resemblance 
in  the  systems  of  occurring  crystalline  forms  ;  transition  from  granular 
varieties  to  compact,  hornstone-like  kinds,  called  felsites,  which  sometimes 
occur  as  rocks;  often  opalescent,  or  having  a  play  of  colors  as  seen  in  a 
direction  a  little  oblique  to  i-l  ;  often  aventurine,  from  the  dissemination 
of  microscopic  crystals  of  foreign  substances  parallel  for  the  most  part  to 
the  planes  O  and  /. 

The  bases  in  the  protoxide  state  are  calcium,  sodium,  potassium,  and  in 
one  species  barium;  the  sesquioxide  base  is  only  aluminum;  the  quantivalent 
ratio  of  R  :  R  is  constant,  1:3;  while  that  of  the  silicon  and  bases  varies 
from  1  ;  1  to  3  :  1,  the  amount  of  silicon  increasing  with  the  increase  of  the 
alkali  metals,  and  becoming  greatest  when  alkalies  are  the  only  protoxides. 

The  included  species  are  as  follows  : 

Crystallization.     Approx.  Q.  ratio  R,R,Si. 

ANORTHITE  Lime  feldspar  Triclinic  1  :  3 

LABRADOKITE  Lime-soda  feldspar  "  1:3 

HYALOPIIANE  Baryta-potash  feldspar  Monoclinic  1  :  3 

ANDESITE  Soda-lime  feldspar  Triclinic  1  :  3 

OLIGOCLASE  k'      "        "  lk  1:39 

ALBITE  Soda  feldspar  "  1  :  3     12 

ORTHOCLASE  Potash  feldspar  Monoclinic  1:3     12 

To  the  above  list  should  be  added,  according-  to  DesCloizeaux,  the  tridinic,  potash  feldspar, 
MICROCLINE,  which  has  the  composition  of  orthoclase. 

The  above  ratios  are  only  approximate,  for  the  analyses  show  a  wide  variation  in  the 
amount  of  silicon,  and  an  exactly  proportionate  variation  in  the  amount  of  alkali  ;  the  two 
elements  vary  in  most  cases,  as  has  been  long  recognized,  according  to  a  simple  law.  There 
seems  hence  to  be  a  gradual  transition  between  the  successive  species  ;  but  this  is  due,  in  part, 
to  mixtures  produced  by  contemporaneous  crystallization  (compare  perthite,  p.  000,  and  the 
description  of  microdine,  p.  000). 

The  unisilicate  ratio  of  1  :  1  for  bases  and  silicon  is  found  in  anorthite  only,  as  shown  above. 
With  Ca  alone,  as  in  this  species,  the  Q.  ratio  for  Al  and  Si  is  3  :  4  ;  with  Na2  alone,  3  :  12; 
and  for  kinds  containing  combinations  of  the  two,  exact  combinations  of  these  ratios,  7wNa2  : 

4ff»+l$B 

ft-Ca,  giving  the  ratio  o  :  —       -  • 
m+n 

An  explanation  of  the  above  fact,  and  of  the  variation  in  ratio  shown  by  analyses,  was  offered 
by  Hunt,  and  has  since  been  developed  by  Tscherrnak.  The  existence  of  two  distinct  triclinic 
feldspars  is  assumed:  anorthite  CaAlSi208,  and  albite  Na.27VlSi6O10,  and  the  other  species 
(sometimes  embraced  under  the  general  term  PLAGIOCLASE)  are  regarded  as  due  to  isomor- 
phous  mixtures  of  these  two  members  in  different  proportions.  They  have  then  the  general 


formula  (Na^O*.)'  For  labradorite  the  ratio  of  m  :  n  is  mostly  3  :  2,  also  3  :  1,  etc.; 
for  andesite  the  ratio  of  m  :  n  varies  about  1  :  2,  and  f  or  oligoclase  the  ratio  of  m  :  n  is  3  :  10, 
also  1  :  3,  etc.  In  accordance  with  the  above  formula,  if  Ca  :  Na=6  :  1,  then  Al  :  Si= 
1  :  2-303  ;  for  Ca  :  Na=3  :  1,  Al  :  Si=l  :  1'257;  for  Ca  :  Na=l  :  1,  Al  :  Si=l  :  3'33  ;  for 
Ca  :  Na=l  :  3,  Al  :  Si  =  l  :  4'4  ;  for  Ca  :  Na=i  :  6,  Al  :  Si=l  :  5. 

This  method  of  viewing  the  feldspar  species  has  the  advantage  of  explaining  the  wide  varia- 
tion in  their  composition,  and  is  generally  accepted  among  German  mineralogists.  DesCloi- 
zeaux regards  his  observations  upon  the  optical  characters  of  the  feldspars  (see  p.  298)  as 
showing  that  they  are  in  fact  distinct  species,  and  not  indeterminate  isornorphous  mixtures. 


298 


DESCRIPTIVE    MINERALOGY. 


Optical  properties  of  the  triclinic  feldspars. — The  following-  table  contains  the  more  import- 
ant optical  properties  of  the  feldspar  species  as  determined  by  DesCloizeaux  (C.  R.,  Feb  8, 
1875,  and  April  17,  1876).  Bx= Bisectrix. 


Acute  bisectrix  .  . 

ANOETHITE. 
always  — 
Position      of 
the  Bx.  has 
no     simple 
relation   to 
the    planes 
observed 
on  the  crvs- 
•tals. 

p  <  v(—  Bx.) 
Inclined. 

84°  58' 
85°  59' 
(Somma) 

LABRADORITE. 
always  + 

30°  40' 
56° 

27°-28° 

37°25'-36'25' 

p  >  ®(  +  Bx.) 
Crossed;  also 
slight  in- 
clined. 

88°  15' 
87°  48' 
(Labrador) 

OLIGOCLASE. 
generally     — 
sometimes  + 

18°  10' 
68° 

Line  parallel 
to  the  edge 
0\i-l. 

(I                     U 

p  <  ®(+Bx.) 
Crossed;  also 
slight  in- 
dined. 

89°  35' 
88C  31' 
(Sunstone, 
Tvedestrand) 

ALBITE. 
always  + 

15° 
78°  35' 

20° 

96°  28'  (front) 
p  <  <+Bx.) 
Inclined  ; 
probably  also 
slight  hori- 
zontal. 

80°  39' 
81°  59' 
(Roc   tourne) 

MICROCLINE. 

always  — 
15°  26' 

5°  6' 

p  <  0(+Bx.) 
Horizontal 
(—  Bx.)    also 
inclined 

(+BX.) 

87"  54' 

Amazonst'ne, 
Mursinsk. 

Angle  made  by  the  +  Bx. 
with  a  normal  to  i-l  (g) 
Same,   with   normal   to 
0(p)  

Angle  made  by  the  line 
in  which  the  plane  of 
the  optic-axes  cuts  i-%, 
with  edge  i-l/0(g'  /p). 
Same,   with  edge  i-l  I 
(a'  m) 

Ordinary  dispersion:  .  .  . 
Parallel  or  perpendicular 
to  plane   of  polariza- 
tion. 

Optic-axial  angle  (in  air) 
for  red  rays  

for  blue  rays  

The  axial  divergence  is  quite  constant  for  albite,  labradorite,  and  anorthite,  but  varies  for 
oligoclase  even  in  different  sections  taken  from  the  same  specimen.  Andesine  (q.  v.)  is 
regarded  by  DesCloizeaux  as  an  altered  oligoclase. 

DesCloizeaux  gives  the  following  method  of  distinguishing  bettceen  tJie  feldspars  by  optical 
means :  It  is  necessary  to  obtain  a  transparent  plate  parallel  to  the  easiest  cleavage  ( 0). 
Such  sections  obtained  from  crystals  or  lamellar  masses  of  aibite,  oligoclase,  labradorite,  and 
the  majority  of  those  of  microcline,  show  hemitropic  bauds,  more  or  less  close  together, 
arranged  along  the  plane  parallel  to  the  second  cleavage  (i-i) ;  for  orthoclase  and  microline 
in  simple  crystals,  two  sections  placed  in  opposite  positions  serve  to  produce  the  same  effect. 
These  sections  are  thus  brought  between  the  crossed  Nicols  of  a  polarization-microscope. 

(1)  For  orthoclase  the  maximum  extinction  takes  place  when  the  two  sections  are  parallel 
to  their  plane  of  contact ;  the  edge  0/i-i  being  in  the  plane  of  polarization  of  the  micro- 
scope. 

(2)  For  microcline,  the  whole  structure  consists  of  a  multitude  of  very  fine  parallel  bands ; 
the  section  may  show  microcline  alone,  either  hemitropic  or  not  hemitropic,  or  microcline  and 
orthoclase  ;  the  extinction  can  take  place  at  30°  54'  between  the  adjoining  bands  of  the  same 
plate  of  the  macle  (microcline  alone),  at  30°  54'  between  the  two  plates  of  the  made  (micro- 
cline in  bands),  or  at  15C  27'  between  the  adjoining  bands  (microcline  and  orthoclase).    In  the 
last  case  the  whole  of  two  lamellae  of  the  macle  show  at  the  same  time  an  extinction  oblique 
to  the  plane  of  composition,  belonging  to  the  microcline,  and  one  parallel  to  this  plane  for  the 
orthoclase. 

(3)  For  albite,  the  extinction  between  two  bands  takes  place  at  an  angle  of  6°  32'. 

(4)  For  oligoclase,  the  extinction  is  simultaneous  in  the  two  bands,  and  when  the  plane  of 
composition  coincides  with  the  plane  of  polarization  of  the  polariscope,  it  shows  that  the 
structure  is  homogeneous. 

(5)  For  labradorite,  the  extinction  takes  place  at  10°  24'  between  the  alternate  lines  of  the 
hemitropic  lamellae. 

It  follows  from  this  that  a  plane  normal  to  the  plane  of  the  axes  cuts  the  base  along  a  line 
making  with  the  edge  O/i-%  the  following  angles : 

0°  in  orthoclase, 
15°  27'  in  microcline, 
3°  16'  in  albite, 
5°  12'  in  labradorite. 

A  variation  of  one  or  two  degrees  from  the  above  mean  angles  was  observed  in 
specimens. 


OXYGEN   COMPOUNDS — ANHYDROUS    SILICATES.  290 

DifF. — The  feldspars  are  distinguished  from  other  species  by  the  characters  already  stated, 
prominent  among  which  are  :  cleavage  in  two  directions,  nearly  or  quite  at  right  angles  to 
each  other  ;  also  hardness,  etc. 

The  triclinic  feldspars  can  in  most  cases  be  distinguished  from  orthoclase  by  the  fine  stria- 
tion  due  to  repeated  twinning.  This  striation  can  often  be  seen  by  the  unaided  eye  upon  the 
cleavage  face  (0).  And  its  existence  can  always  be  surely  tested  by  the  examination  of  a  thin 
section  in  polarized  light,  the  alternate  bands  of  color  showing  the  same  fact. 

The  separation  of  the  different  triclinic  species  can  be  surely  made  by  complete  analysis 
only,  or  at  least  by  the  determination  of  the  amount  of  alkali  present.  The  degree  of  fusi- 
bility, the  color  of  the  flame,  and  the  effect  produced  by  digestion  in  acids,  are  often  import- 
ant aids.  In  the  hands  of  a  skilled  observer  the  optical  examination  may  give  decisive  results. 


ANORTHITE.     Indianite.       .      . 

Triclinic.  c\l:a  =  0-86663  :  1-57548  :  1.  /A  1'  =  120°  31',  O  A 
(over  2-£)  =  94°  10',  O  f\  I'  =  114°  6i',  O  A  7=  110° 
40',  0  A  24  =  98°  46'  ;  a  =  93°  13£',  ft  =  115°  55J-', 
7  =  91°  Hi'  Cleavage  :  O,  i-l  perfect,  the  latter 
least  so.  Twins  similar  to  those  of  albite.  Also  mas- 
sive. Structure  granular,  or  coarse  lamellar. 

H.=6-7.  (3-.=2-6ti-2-78.  Lustre  of  cleavage 
planes  inclining  to  pearly  ;  of  other  faces  vitreous. 
Color  white,  grayish,  reddish.  Streak  uncolored. 
Transparent  —  translucent.  Fracture  conchoidal. 
Brittle. 

Var. — Anorthite  was  described  from  the  glassy  crystals  of  Som- 

ma.     Indianite  is  a  white,  grayish,  or  reddish  granular  anorthite  from  India,  first  described 
in  1802  by  Count  Bourn  on. 

Comp.— Q.  ratio  for  R  :  Al  :  Si=l  :  3  :  4.  Formula  CaMSi2O8= Silica  43-1,  alumina  36-8, 
lime  20' 1  —  100.  The  alkalies  are  sometimes  present  in  very  small  amounts. 

Pyr.,  etc. — B.B.  fuses  at  5  to  a  colorless  glass.  Decomposed  by  hydrochloric  acid,  with 
separation  of  gelatinous  silica. 

Obs. — Occurs  in  some  granites;  occasionally  in  connection  with  gabbro  and  serpentine 
rocks ;  in  some  cases  along  with  corundum  ;  in  many  volcanic  rocks.  Found  in  the  old  lavas 
in  the  ravines  of  Monte  Somma ;  Pesmeda-Alp,  Tyrol;  in  the  Faroe  islands;  in  Iceland; 
near  Bogoslovsk  in  the  Ural,  etc. 

BYTOWNITE  has  been  shown  by  Zirkel  to  be  a  mixture.     Bytown,  Canada. 


LABRADORITE. 

Triclinic.  1 A  T  =  121°  37',  O  A  i4  =  93°  20',  O  A  /  =  110°  50',  0  A  T 
=  113°  34' ;  Marignac.  Twins  :  similar  to  those  of  albite.  Cleavage :  O 
easy ;  i-l  less  so ;  /  traces.  Good  crystals  rare  ;  generally  massive  granular, 
and  in  grains  cleavable ;  sometimes  cryptocrystalline  or  hornstone-like. 

H.  =  6.  G.:=2'67-2'76.  Lustre  of  O  pearly,  passing  into  vitreous; 
elsewhere  vitreous  or  subresinous.  Color  gray,  brown,  or  greenish,  some- 
times colorless  and  glassy ;  rarely  porcelain- white ;  usually  a  change  of 
colors  in  cleavable  varieties.  Streak  uncolored.  Translucent — subtrans- 
lucent. 

Comp.,  Var — Q.  ratio  for  R  :  Al :  Si— 1  :  3  :  6,  but  varying  somewhat  (see  p.  297). 
Formula  RAlSi3Oi0;  here  R=Ca  and  Na2.  The  atomic  ratio  for  Na  :  Ca— 2  :  3  generally, 
this  corresponds  to  Silica  52-9,  alumina  30 '3,  lime  12 '3,  soda  4*5=100. 

Var.  1.   Cleavable.     (a)  Well  crystallized  to  (b)  massive.     Play  of  colors  either  wanting,  as 


300  DESCRIPTIVE   MINERALOGY. 

in  some  colorless  crystals ;  or  pale  ;  or  deep ;  blue  and  green  are  the  predominant  colors  ;  but 
yellow,  fire-red,  and  pearl-gray  also  occur.  By  cutting  very  thin  slices,  parallel  to  i-l,  from 
the  original  labradorite,  they  are  seen  under  the  microscope  to  contain,  besides  strise,  great 
numbers  of  minute  scales,  like  the  aventurine  oligoclase,  which  are  probably  gothite  or  hema- 
tite. These  scales  produce  an  aventurine  effect  which  is  quite  independent  of  the  play  of 
colors  which  arises  from  the  interference  of  the  rays  of  light  reflected  by  innumerable  inter- 
nal lamelise  (ReuucJi).  The  various  forms  of  minerals  (micropbik&ea,  microphyllites,  etc. )  en- 
closed in  the  labradorite,  and  their  relation  to  it  in  position,  have  been  thoroughly  investigated 
by  Schrauf  (Ber.  Ak.,  Wien,  Dec.,  1869). 

Pyr,,  etc. — B.B.  fuses  at  3  to  a  colorless  glass.  Decomposed  with  difficulty  by  hydrochloric 
acid,  generally  leaving  a  portion  of  undecomposed  mineral. 

Obs. — Labradorite  is  a  constituent  of  some  rocks,  both  metamorphic  and  igneous;  e.g., 
diabase,  doleryte,  basalt,  etc.  The  labradoritic  metamorphic  rocks  are  most  common  among 
the  formations  of  the  Archa3an  or  pre-Silurian  era.  Such  are  part  of  those  of  British  America, 
northern  New  York,  Pennsylvania,  Arkansas;  those  of  Greenland,  Norway,  Finland,  Sweden, 
and  probably  of  the  Vosges.  Being  a  feldspar  containing  comparatively  little  silica,  it  occurs 
mainly  in  rocks  which  include  little  or  no  quartz  (free  silica). 

Kiew  has  furnished  fine  specimens  ;  also  Labrador.  It  is  met  with  in  many  places  in 
Canada  East.  Occurs  at  Essex  Co.,  N.  Y.  ;  also  in  St.  Lawrence,  Warren,  Scoharie,  and 
Green  Cos.  In  Pennsylvania,  at  Mineral  Hill,  Chester  Co.  ;  in  the  Witchita  Mts.,  Arkansas, 
etc. 

Labradorite  was  first  brought  from  the  Isle  of  Paul,  on  the  coast  of  Labrador,  by  Mr.  Wolfe, 
a  Moravian  missionary,  about  the  year  1770,  and  was  called  by  the  early  mineralogists  Labra- 
dor stone  (Labradorstein),  and  also  chatoyant,  opaline,  or  Labrador  feldspar.  Labradorite 
receives  a  fine  polish,  and  owing  to  the  chat  ryant  reflections,  the  specimens  are  often  highly 
beautiful.  It  is  sometimes  used  in  jewelry. 

MASKELYNITE. — Occurs  in  transparent,  isometric,  grains  in  the  meteorite  of  Shergotty. 
Same  composition  as  labradorite. 


ANDESITE.    Andesine. 

Triclinic.  Approximate  angles  from  Esterel  crystals  (DesCL):  O  A«-£, 
left,  87°-88°,OA/=:lll0-1120,  (9  A/ =  115°,  If\i-i  =  119°-120°,  /' M-l 
=120°,  0A2-fc  =  101°-1020.  Twins:  resembling  those  of  albite.  Sel- 
dom in  crystals.  Cleavage  more  uneven  than  in  albite.  Also  granular 
massive. 

H.=5-6.  G.^2'61-2'74:.  Color  white,  gray,  greenish,  yellowish,  flesh- 
red.  Lustre  subvitreous,  inclining  to  pearly. 

Oomp.— Q.  ratio  1:3:8,  but  varying  to  1  :  3  :  7.  General  formula  RAlSi4OiQ ;  R=Na2  and 
Ca  in  the  ratio  1  :  1  to  3  :  1 ;  if  the  ratio  is  1  :  1,  the  formula  corresponds  to  Silica  59 '8,  alu- 
mina 25-5,  lime  7'0,  soda  7  -7=100. 

Pyr.,  etc. — Andesite  fuf-es  in  thin  splinters  before  the  blowpipe.  Saccharite  melts  only  on 
thin  edges  ;  with  borax  forms  a  clear  glass.  Imperfectly  soluble  in  acids. 

Obs. — Occurs  in  many  rocks,  especially  some  trachytes.  The  original  locality  was  in  the 
Andes,  at  Marmato ;  also  in  the  porphyry  of  1'Esterel,  France  ;  in  the  Vosges  Mts.  ;  at  Vap- 
nefiord,  Iceland,  in  honey-yellov/  transparent  crystals,  etc.  In  North  America,  found  at 
Chlteau  Richer,  Canada,  forming  with  hypersthene  and  ilmenite  a  wide-spread  rock ;  color 
flesh-red.  .- 

Andesite  is  regarded  by  DesCloizeaux  as  an  altered  oligoclase,  but  many  careful  analyses 
point  to  a  feldspar  having  the  composition  given  above. 


HYALOFHANE. 

Monoclinic,  like  orthoclase,  and  angles  nearly  the  same.  6y=64016', 
/A  /  =  118°  41',  O  A  l-i  =  130°  55$'.  Cleavage  :  0  perfect,  i-l  somewhat 
less  so.  In  small  crystals,  single,  or  in  groups  of  two  or  three. 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


301 


H.=6-6*5.  Gr. = 2*80,  transparent ;  2*905,  translucent.  Lustre  vitreous, 
or  like  that  of  adnlaria.  Color  white,  or  colorless ;  also  flesh-red.  Trans- 
parent to  translucent. 

Comp.— Q.  ratio  f  or  R  :  R  :  Si=l  :  3  :  8.  Formula  (Ba,K2)AlSi4Oi2.  Analysis  of  hyalo- 
phane  from  the  Binnenthal  by  Stockar-Escher,  Si02  52'67,  A1O3  21-12,  MgO  0'04,  CaO  0-46, 
BaO  15-05,  Na2O  214,  K2O  7-82,  H20  0 '58  =  99  -88. 

Pyr.,  etc. — B.B.  fuses  with  difficulty  to  a  blebby  glass.     Unacted  upon  by  acids. 

Obs. — Occurs  in  a  granular  dolomite  near  Imfeld,  in  the  Binnenthal,  Switzerland  ;  also  at 
Jakobsbergin  Sweden. 


OLIGOCLASB. 

Triclinic.    /A  T  =  120°  42',  O  A  i-l,  ov.  2-5'  =  93°  50',  0  A  /=  110°  55', 
O  A  I  =  114°  40'.     Cleavage  :  O,  i-l  perfect,  the 
latter  least  so.     Twins :  similar  to  those  of  albite. 
Also  massive. 

H.=6-7.  G.=2-56-2-72;  mostly  2-65-2-69. 
Lustre  vitreo-pearly  or  waxy,  to  vitreous.  Color 
usually  whitish,  with  a  faint  tinge  of  grayish- 
green,  grayish- white,  reddish-white,  greenish, 
reddish ;  sometimes  aventurine.  Transparent, 
subtranslucent.  Fracture  conchoidal  to  uneven. 

Comp.,  Var.—Q.  ratio  for  R  :  Al  :  Si  =  l  :  3  :  9,  though 
with  some  variations  (see  p.  297).  Formula  RAlSi5Oi4,  with 
R=:Na(K2),Ca.  The  ratio  of  3  :  1  for  Na  :  Ca  corresponds  in 
this  formula  to  Silica  61  -9,  alumina  24 '1,  lime  5'2,  soda  8-8=100. 

Var.  1.  Gleamble  ;  in  crystals  or  massive.  2.  Compact  massive ;  oligodase-feUite  ;  includes 
part,  at  least,  of  the  so-called  compact  feldspar  orfelsite,  consisting  of  the  feldspar  in  acorn- 
pact,  either  fine  granular  or  flint-like  state.  3.  Aventurine  oligodase,  or  sunstone.  Color 
grayish-white  to  reddish-gray,  usually  the  latter,  with  internal  yellowish  or  reddish  fire-like 
reflections  proceeding  from  disseminated  crystals  of  probably  either  hematite  or  gothite.  4. 
Moonstone  pt.  A  whitish  opalescence. 

Pyr.,  etc.— B.B.  fuses  at  3'5  to  a  clear  or  enamel-like  glass.  Not  materially  acted  upon  by 
acid?. 

Obs. — Occurs  in  porphyry,  granite,  syenite,  serpentine,  and  also  in  different  eruptive  rocks. 
It  is  sometimes  associated  with  orthoclase  in  granite,  or  other  granite-like  rocks.  Among  its 
localities  are  Pargas  in  Finland  ;  Schaitansk,  Ural ;  in  protogine  of  the  Mer-de-G-lace,  in  the 
Alps ;  in  fine  crystals  at  Mb.  Somma  ;  as  sunstone  at  Tvedestrand,  Norway ;  in  Iceland, 
colorless,  at  Hafnefjord  (Jwfnefiordite).  In  the  United  States,  at  Unionville,  Pa.  ;  also  at 
Haddam,  Ct.  ;  Mineral  Hill,  Delaware  Co.,  Pa.  ;  at  the  emery  mine,  Chester,  Mass. 

Named  in  1826  by  Breithaupt  from  o'.iyor*  little,  and  /c/Uw,  to  cleave. 

TSCHERMAKITE  (v.  Kobell). — Supposed  to  be  a  magnesia-feldspar,  but  the  conclusion 
was  probably  based  on  the  analysis  of  impure  material.  Later  investigations  (Hawes,  Pisani) 
make  it  an  oligoclase.  Occurs  with  kjerulfine  from  Bamle,  Norway. 


ALBITE. 

Triclinic.  /  A  T  =  120°  47',  O  A  i-l  =  93°  36',  0  A  T  =  114°  42',  O  A  1 
=  110°  5(X,  0A2-r=136°  50',  O  A 2-8  =  133°  14'.  Cleavage:  O,  i-l 
perfect,  the  first  most  so;  14  sometimes  distinct.  Twins:  twinning-plane 
i-$,  axis  of  revolution  normal  to  *'-£,  this  is  the  most  common  method,  and 
its  repetition  gives  rise  to  the  fine  striations  (p.  91)  upon  the  plane  O,  whicli 
are  so  characteristic  of  the  triclinic  feldspars ;  twinuing-plane,  2-£  (f.  578) 


302 


DESCRIPTIVE   MINERALOGY. 


analogous  to  the  Baveno  twins  of  orthoclase  ;  also  twinning-axis,  the  vertical 
axis  (f.  575) ;  twinning-axis,  the  macrodiagonal  axis*  (5),  the  peridine  twins. 
Double  twins  not  uncommon.  True  simple  crystals  very  rare.  Also  mas- 
sive, either  lamellar  or  granular ;  the  laminae  sometimes  divergent ;  granular 
varieties  occasionally  quite  fine  to  impalpable. 


573 


574 


575 


578 


579 


Pericline. 


Middletown,  Ct. 


II.  =  6-7.  G.  =  2-  59-2-65.  Lustre  pearly  upon  a  cleavage  face  ;  vitreous 
in  other  directions.  Color  white,  also  occasionally  bluish,  gray,  reddish, 
greenish,  and  green  ;  sometimes  having  a  bluish  opalescence  or  play  of  colors 
on  O.  Streak  uncolored.  Transparent—  subtranslucent.  Fracture  uneven. 
Brittle. 

Comp.,  Var  —  Q.  ratio  Na  :  Al  :  Si=l  :  3  :  12.  Formula  Na2AlSi6O16—  Silica  68'6,  alumina 
19-6,  soda  11'8  =  100.  A  small  part  of  the  sodium  is  replaced  usually,  if  not  always,  by 
potassium,  and  also  by  calcium  (here  Na2  by  Ca).  But  these  differences  are  not  externally 
apparent. 

Var.  1.  Ordinary,  (a)  In  crystals  or  cleavable  massive.  The  angles  vary  somewhat, 
especially  for  plane  7'.  (1}  Aventuri/ie  ;  similar  to  aventurine  oligoclase  and  orthoclase.  (c) 
Moonstone  ;  similar  to  moonstone  under  oligoclase  and  orthoclase.  Peristerite  is  a  whitish 
adularia-like  albite,  slightly  iridescent,  having  G.  =2'H26  ;  named  from  Trepiarepd,  pigeon,  the 
colors  resembling  somewhat  those  of  the  neck  of  a  pigeon,  (d)  Peridine  is  in  large,  opaque, 
white  crystals,  short  and  broad,  of  the  forms  in  f.  577  (f.  334,  p.  101)  ;  from  the  chlorite  schists 
of  the  Alps.  Lamellar  ;  cleavelandite,  a  white  kind  found  at  Chesterfield,  Mass. 

Pyr.,  etc.  —  B.B.  fuses  at  4  to  a  colorless  or  white  glass,  imparting  an  intense  yellow  to  the 
flame.  Not  acted  upon  by  acids. 

Obs.  —  Albite  is  a  constituent  of  several  rocks,  as  dioryte,  etc.  It  occurs  with  orthoclase  in 
some  granite.  It  is  common  also  in  gneiss,  and  sometimes  in  the  crystalline  schists.  Veins 
of  albitic  granite  are  often  repositories  of  the  rarer  granite  minerals  and  of  fine  crystalliza- 
tions of  gems,  including  beryl,  tourmaline,  allanite,  columbite,  etc.  It  occurs  also  in  some 
trachyte,  in  phonolyte,  in  granular  liniestone  in  disseminated  crystals,  as  near  Modane  in 
Savoy.  Some  localities  for  crystals  are  :  Schneeberg  in  Passeir,  in  simple  crystals  ;  Col  du 
Bonhomme  ;  St.  Gothard,  and  elsewhere  in  the  Alps  ;  Penig,  etc.  ,  Saxony  ;  Arendal  ;  Green- 
land ;  Island  of  Elba. 

In  the  U.  S.  ,  in.  Maine,  at  Paris.  In  Mas*.  ,  at  Chesterfield  ;  at  Goshen.  In  Conn.  ,  at 
Haddam  ;  at  Middletown.  In  N.  York,  at  Granville,  Washington  Co.  ;  at  Moriah,  Essex  Co. 
In  Penn.,  at  Unionville,  Delaware  Co. 

The  name  Albite  is  derived  from  albus,  white,  in  allusion  to  its  color,  and  was  given  the 
species  by  Gahn  and  Berzelius  in  1814. 


*  Vom  Rath  has  recently  shown  this  to  be  the  true  method  of  twinning  in  this  case,  and 
hence  that  the  explanation  of  Rose  (given  on  p.  101)  is  incorrect. 


OXYGEN   COMPOUNDS  —  ANHYDROUS    SILICATES. 


303 


ORTHOCLASE. 

Monoclinic.  C=  63°  53',  /A  1=  118°  48',  0  A  14  =  153°  28';  c  :  b  :  d 
=  0-84:4:  :  1-5183  :  1.  O  A  l-i  =  129°  41',  6>  A  2-i  =  99°  38',  O  A  2  =  98° 
4'.  Cleavage  :  0  perfect ;  i-l  less  distinct ;  i-i  faint ;  also  imperfect  in  tlie 
direction  of  one  of  the  faces  /.  Twins:  twinning-plane,  i-i  (Carlsbad 
twins)  f.  582,  but  the  clinopinacoid  (i-l)  the  composition-face  (see  p.  98) ; 
twinning-plane  the  base  (O)  f.  583  ;  also  the  clinodorne,  24  (JBaveno  twins), 
as  in  f.  588,  in  which  the  prism  is  made  np  of  two  adjoining  planes  O  and 
two  i-l,  and  is  nearly  square,  because  O  A  i-l  =  90°,  and  O  A  24  =  135°  3' ; 
/A  /—  169°  28' ;  also  the  same  in  a  twin  of  4  crystals,  f .  587,  each  side  of 
the  prism  then  an  O  (see  also  p.  99).  Often  massive,  granular ;  sometimes 
lamellar.  Also  compact  crypto-crystalline,  and  sometimes  flint-like  or 
jasper-like. 


580 


581 


582 


583 


588 


Loxoclase. 

H.^6-6-5.  Gr.  =  2-44-2-62,  mostly  2-5-2-6.  Lustre  vitreous;  on  cleav- 
age-surface sometimes  pearly.  Color  white,  gray,  flesh-red,  common ; 
greenish- white,  bright-green.  Streak  un colored.  Transparent  to  trans- 
lucent. Fracture  conchoidal  to  uneven.  Optic-axial  plane  sometimes  in 
the  orthodiagonal  section  and  sometimes  in  the  clinodiagonal ;  acute  bisec- 
trix always  negative,  normal  to  the  orthodiagonal. 

Compi.,  Var. — Q.  ratio  for  K  :  Al  :  Si=l  :  3  :  12.  Formula  K2AlSir)O16  =  Silica  64 •?,  alu- 
mina 18  4,  potash  16'9  — 100;  with  sodium  sometimes  replacing  part  of  the  potassium.  The 
orthoclase  of  Carlsbad  contains  rubidium.  The  varieties  depend  mainly  on  structure,  varia- 
tions in  angles,  the  presence  of  soda,  and  the  presence  of  impurities. 

The  amount  of  sodium  detected  by  analyses  varies  greatly,  the  variety  sanidin  (see  below) 
sometimes  containing  6  per  cent.  The  variations  in  angles  are  large,  and  they  occur  some- 
times even  in  specimens  of  the  same  locality.  The  crystallization  is  normally  monoclinic, 
and  the  variations  are  simply  irregularities.  There  are  also  large  optical  variations  in  ortho- 
clase, on  which  see  DesCl.  Min.,  i. ,  329. 

Var.  1.  Ordinary.  In  crystals,  or  cleavable  massive.  Adularia  (adular).  Transparent, 
cleavable,  usually  with  pearly  opalescenfc  reflections,  and  sometimes  with  a  play  of  colors  like 
labradorite,  though  paler  in  shade.  Moonstone  belongs  in  part  here,  the  rest  being  albite  and 
oligoclase.  SuntstoitC,  or  ave/it urine  feldspar :  In  part  ortboclase,  rest  albite  or  oligoclase 
(q.  v.).  Amaeonstone:  Bright  verdigris-green,  and  cleavable,  mostly  mixtures  of  orthoclase 
and  microcliue  (Dx.).  Koenig  concludes  that  the  coloring  matter  of  the  Pike's  Peak  amazon- 
stone  is  an  organic  compound  of  iron,  which  has  been  infiltrated  into  the  mass. 

Sanidin  of  Nose',  or  glassy  feldspar  (including  much  of  the  Ice-spar,  part  of  which  is  anor- 


304  DESCRIPTIVE   MINERALOGY. 

thite).  Occurs  in  transparent  glassy  crystals,  mostly  tabular  (whence  the  name  from  oavic,  a 
board),  in  lava,  pumice,  trachyte,  phonolite,  etc.  Proportion  of  soda  to  potash  varies  from 
1  :  20  to  2  :  1.  Wiyacolite  is  the  same  ;  the  name  was  applied  to  glassy  crystals  from  Mt. 
Somma  (Eisspath,  Wern.). 

Chesterlite.  In  white  crystals,  smooth,  but  feebly  lustrous,  implanted  on  dolomite  in  Ches- 
ter Co. ,  Penn.,  and  having  wide  variations  in  its  angles.  It  contains  but  little  soda.  Accord- 
ing to  DesCloizeaux  the  chesterlite  consists  of  a  union  of  parallel  bands  of  orthoclase  and  a 
triclinic  feldspar  of  the  same  composition,  which  he  calls  microdine  (see  below). 

Loxodase.  In  grayish-white  or  yellowish  crystals,  a  little  pearly  or  greasy  in  lustre,  often 
large,  feebly  shining,  lengthened  usually  in  the  direction  of  the  clinodiagonal.  0  A  l=\\fr 
30',  0AJ'  =  112°  50',  lAl'=l2Q°  20',  0 f\i-l  (cleavage  angle) =90°,  Breith.  G.=2-6-2'62, 
Plattner.  The  analyses  find  much  more  soda  than  potash,  the  ratio  being  about  3:1,  but 
how  far  this  is  due  to  mixture  with  albite  has  not  been  ascertained.  From  Hammond,  St. 
Lawrence  Co.,  N.  Y.  Named  from  Ao^?,,  transverse,  and  /cAa«,  I  cleave,  under  the  idea  that 
the  crystals  are  peculiar  in  having  cleavage  parallel  to  the  orthodiagonal  section.  Perthite. 
A  flesh-red  aventurine  feldspar,  consisting  of  interlaminated  albite  and  orthoclase,  as  shown 
by  Breithaupt.  From  Perth,  Canada  East. 

COMPACT  ORTHOCLASF]  or  ORTHOCLASE-FELSITE. — This  crypto-crystalline  variety  is  com- 
mon and  occurs  of  various  colors,  from -white  and  brown  to  deep  red.  There  are  two  kinds 
(a)  the  jasper-like,  with  a  subvitreous  lustre  ;  and  (b)  the  ceratoid  or  wax-like,  with  a  waxy 
lustre.  Some  red  kinds  look  closely  like  red  jasper,  but  are  easily  distinguished  by  the  fusi- 
bility. The  orthoclase  differs  from  the  albite  felsite  in  containing  much  more  potash  than 
soda.  The  Swedish  name  Halleflinta  means  false  flint. 

Pyr.,  etc.— B.B.  fuses  at  5  ;  varieties  containing  much  soda  are  more  fusible.  Loxoclase 
fuses  at  4.  Not  acted  upon  by  acids. 

Obs. — Orthoclase  is  an  essential  constituent  of  many  rocks  ;  here  are  included  granite, 
gneiss,  and  mica  schist;  also  syenite,  trachyte,  phonolyte,  etc.,  etc. 

Fine  crystals  are  found  at  Carlsbad  in  Bohemia ;  Katherinenburg,  Siberia  ;  Arendal,  Nor- 
way ;  Baveno  in  Piedmont ;  in  Cornwall ;  in  the  Urals  ;  the  Mourne  mountains,  Ireland,  etc. ; 
in  the  trachyte  of  the  Drachenfels  on  the  Rhine.  In  the  U.  States,  orthoclase  is  found  in 
N.  Hamp. ,  at  Acworth.  In  Conn. ,  at  Haddam  and  Middletown.  In  N.  York,  at  Rossie  ; 
in  the  town  of  Hammond ;  in  Lewis  Co. ;  near  Natural  Bridge  ;  in  Warwick ;  and  at  Amity 
and  Edenville.  In  Penn.,  in  crystals  at  Leiperville,  Delaware  Co.,  etc.  In  N.  Car.,  at 
Washington  Mine,  Davidson  Co.;  beautiful  Amazonstone  at  Pike's  Peak,  Col.  Massive  ortho- 
clase is  abundant  at  many  localities. 

MICROCLINE.  A  triclinic  potash  feldspar. — The  name  microdine  was  originally  given  by 
Breithaupt  to  a  whitish  or  reddish  feldspar  from  the  zircon-syenite  of  Fredericksvarn  and 
Brevig,  Norway,  on  the  ground  that  it  was  triclinic.  It  was  shown  by  DesCloizeaux  that  this 
feldspar  was  merely  a  variety  of  orthoclase  remarkable  for  its  large  amount  of  soda.  Recently 
the  latter  author  has  proposed  to  retain  this  name  for  a  feldspar  found  in  the  midst  of  gran- 
ites, pegmatite,  and  gneiss,  which  is  shown  both  by  the  angle  between  its  cleavage  planes, 
and  also  by  its  optical  properties,  to  be  really  triclinic. 

Form  generally  like  that  of  orthoclase.  Cleavage  basal  and  clinodiagonal,  and  also  easy 
parallel  to  both  prismatic  faces  (1  and  1');  for  the  optical  properties  see  p.  298.  Often  asso- 
ciated with  orthoclase  in  regular  parallel  bands,  especially  in  the  amazonstone  ;  albite  is  also 
hometimes  present,  though  irregularly.  Analysis  of  a  "pure  microdine  "  from  Magnet  Cove 
byPisani.  G.=2-54. 

SiO2  A103  FeO3  K.O  Na2O  ign. 

64-30  19-70  0-74  15  "60  0'48  0-35=101  -17 

The  association  of  orthoclase  and  microdine  was  observed  in  specimens  from  the  Ilmen 
Mts.;  Urals ;  Arendal ;  Greenland ;  Labrador  ;  Everett,  Mass.;  Delaware,  Chester  Co.,  Penn.; 
Pike's  Peak,  Col.  The  purest  microdine  was  that  of  a  greenish  color  from  Magnet  Cove, 
Ark.  ;  it  enclosed  crystals  of  segirite,  and  was  not  mixed  with  orthoclase. 

SuBSILICATES. 

Humite  or  Chondrodite  Group,  including  three  sub-species  : 

I.  Humite;  II.   Chondrodite;  III.  Clinohumite. 

The  existence  of  three  types  of  forms  among  the  crystals  of  humite  (Vesuvius)  was  early 
shown  by  Scacchi ;  they  have  since  then  been  further  investigated  by  vom  Rath  (Pogg.  Erg., 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


305 


Bd.  v.,  321,  1871  ;  ibid.,  vi.,  385,  1873).  The  chemical  identity  of  the  species  humite  and 
chondrodite  was  shown  by  Ramrnelsberg  ;  later  Kokscharof  proved  that  the  crystals  of  chon- 
drodite  from  Pargas,  Finland,  were  identical  in  form  and  angles  with  Scacchi' s  type  II,  of 
humite,  and  the  same  has  also  been  shown  of  the  Swedish  crystals  by  vom  Rath.  In  1875 
the  author  described  crystals  of  chondrodite  from  Brewster,  N.  Y. ,  belonging  to  each  of  the 
three  types  of  humite  ;  he  showed,  moreover,  then  and  later  (Feb.,  1876),  that  contrary  to 
what  had  been  previously  assumed,  the  crystals  of  both  type  II.  and  type  III.  were  monoclinic, 
not  orthorhombic.  DesCloizeaux  and  Klein  have  since  proved  (Jahrb.  Min.,  1876,  No.  6) 
th,e  monoclinic  character  of  type  III.  of  the  Vesuvian  humite,  and  the  former  that  of  the 
Swedish  crystals  (type  II.)  ;  he,  moreover,  proved  the  orthorhombic  character  of  the  crystals 
of  type  I. ,  Vesuvius.  In  accordance  with  these  facts  DesCloizeaux  has  proposed  that  the  three 
types  be  regarded  as  distinct  species,  with  the  names  given  above. 


I.  HUMITE.     Including  type  I.  ,  Scacchi,  Vesuvius.    Also  rare  crystals  from  Brewster,  N.  Y. 
The  latter  large,  coarse,  and  having  suffered  more  or  less  alteration. 


Orthorliombic.  Holohedral.  i-2  (o2)  A  i~2  =  130°  19';  O  (A)  A  3-1  (?)  — 
102°  4:8'  ;  O  A  14  (i2)  =  124°  16'  ;  O  A  34  (e5)  =  103°  47'  ;  0  A  14  (es)  =  126° 
21'  ;  0  A  1-2  (Vs)  =  121°  44'.  Twins  :  twinning-plane  -|4,  also  f  4,  in  both 
cases  the  angle  of  the  horizontal  prism  is  nearly  120°.  Optic-axial  plane 
parallel  to  the  base,  acute  bisectrix  positive,  normal  to  i-1.  Dispersion 
almost  zero.  2Ha  =  78°  18'  -79°  for  red  rays.  (DesCl.) 


590 


592 


Vesuvius. 


Brewster. 


Brewster. 


II.  CHONDRODITE.   Including  type  II.  of  Scacchi,  Vesuvius  ;  also  crystals  from  Finland, 
Sweden,  and  with  few  exceptions  those  of  Brewster,  N.  Y. 


Monoclinic.  A  A  i  —  122°  29';  A  A  e2  =  109°  5';  J.  A  #'  —  108°  58'; 
-A:?*8  =103°  12';  A  /\n2'  =  103°  9';  A  A  r1  =  135°  20';  ^.Ar8  =  125° 
50';  <7  A  r8  =  146°  24';  6yA  w,8  =  135°  40' :  C l\rij  =  135°  41'. 

The  letters  (those  employed  by  Scacchi)  correspond  to  the  following 
symbols  : — 

A  =  0    i  =  14   e2  =  —24   n2  =  —  2   7-1  =  — 4~S   r5—  — 
C  =  i-l    #=£4   e2'—      2-i   ?i8'=   '2   r^ 

Twins  :  twinning  plane  \-i  (±?)  and  f4  (±?),  (both  having  a  prismatic 
angle  nearly  120°) ;  also  the  basal  plane  O  (Brewster,  K  Y.,  I.  593). 
Optic-axial  plane  makes  an  angle  of  26°  with  the  base ;.  acute  bisectrix 

20 


306 


DESCRIPTIVE   MINERALOGY. 


positive,  normal  to  the  clinopinacoid  (C).     2Ha=88°  48'  for  red  rays, 
Brewster,  K  Y.  (E.  S.  D.).  2Ha=86°  14'-87°  20'  (red  rays),  Sweden,  (DesCl.) 

The  above  angles  are  those  given  by  DesCloizeaux,  the  author's  own  measurements  on  the 
crystals  from  Brewster  (not  yet  completed),  point  to  a  smaller  variation  from  the  rectangular 
type.  DesCloizeaux  makes  the  plane  er=i-i^  and  r4— 7,  r2=l,  r3—  — 1. 


595 


Brewster. 


Brewster. 


Vesuv  us 


III.  CLINOHUMITE.    Including  type  III.  of  Scacchi,  Vesuvius ;  also  rare  finely  polished 
red  crystals  from  Brewster,  N.  Y. 

Monoclinic.  A  A  e2  =  133°  40' ;  A  A  e2'  =  133°  40' ;  A  A  ^2  =  125°  13' ; 
At\m  =  114°  55' ;  A  A  m2  =  92°  58' ;  A  A  n  =  132°  14' ;  A  A  n2  =  122° 
57';  ^A?i4  =  97°  23';  A/\n*f  =  97°  23' ;  ^4  A  r3  =  131°  23  ;  A  A?-4  =  125° 
47' ;  <7A  r3  =132°  56' ;  C f\  r*  =  137°  25'.  DesCloizeaux. 

These  letters  (those  employed  by  Scacchi)  correspond  to  the  following 
symbols : — 

A—O      i  —\-\     n—     4-    n^——  4 


DesCloizeaux  makes  the  plane  <?4'  =  i-i,  r8  —  /,  and  r*  =  —  1,  and  r5  =  1. 
Twins:  twinning-plane  —  f-a;  also  the  basal  plane  (Brewster).  Optic-axial 
plane  makes  an  angle  of  7-2°  with  the  base,  Brewster  (Dana)  ;  same  angle 
for  Yesuvian  crystals  equals  12°  28'  (Klein),  about  11°  (DesCl.X  Acute 
bisectrix  positive,  normal  to  clinopinacoid.  2Ha=84°  40'-85°  15',  yellow 
(Kl.).  =  84°  38'-85°  4'  white  crystals,  and  =86°  40'-87°  14'  brown  crystals 
(DesCl.).  Sections  of  crystals  often  shows  a  complex  twinned  structure. 

In  other  physical  and  in  chemical  characters  these  three  sub-species  are 
hardly  to  be  distinguished. 

H.=6-6-5.  G.=3-118-3-24.  Lustre  vitreous— resinous.  Color  of 
crystals  yellowish-white,  citron-yellow,  honey-yellow,  hyacinth-red,  brownish 
(Vesuvius) ;  also  deep  garnet-red  (Brewster).  Color  of  the  mineral  occur- 
ring massive  and  in  rounded  imbedded  grains  (chondrodite  at  least  in  part) 
as  of  crystals,  also  sometimes  olive-green,  apple-green,  gray,  black.  Streak 
white,  or  slightly  yellowish,  or  grayish.  Transparent — subtranslucent. 
Fracture  subconchoidal — uneven. 


OXYGEN   COMPOUNDS ANHYDROUS    SILICATES. 


307 


Comp. — The  chemical  investigations  of  Rammelsberg  and  vom  Rath  have  served  to  show 
a  considerable  variation  in  composition  in  the  different  varieties,  but  do  not  give  decidedly 
different  formulas  to  the  three  types  of  Scacchi,  that  is,  the  three  minerals  described  above. 

In  general  Q.  ratio  for  Mg  :  Si=4  :  3  (1£  :  1),  and  the  formula  then  Mg6Si3Oi4  ;  or,  as  pre- 
ferred by  Rammelsberg,  Mg  :  Si=5  :  4  (1^  :  1),  and  the  formula  is  then  Mg5Si2O9.  In  all 
cases  part  of  the  magnesium  is  replaced  by  iron,  and  part  of  the  oxygen  by  fluorine  (F2),  the 
amount  varying  from  2$  to  8J  p.  c.,  but  certainly  not  dependent  (v.  Rath  and  Ramm.)  upon 
the  three  types. 
Analyses : — • 

SiOo     FeO    MffO       F 

CaO  0-23  A103  0-82=99-68,  v.  Rath. 
CaO  0-74  -MO3  I'06=100'82,  Ramm. 

A103  0-48=99-72,  Hawes. 

A1O3  0-72=99-26,  v.  Rath. 

A1O3  0-24=99-86,  v.  Rath. 

=101-68,  Ramm. 

Pyr.,  etc. — B.B.  infusible  ;  some  varieties  blacken  and  then  burn  white.  Fused  with  salb 
of  phosphorus  in  the  open  tube  gives  a  reaction  for  fluorine.  With  the  fluxes  a  reaction  for 
iron.  Gelatinizes  with  acids.  Heated  with  sulphuric  acid  gives  off  silicon  fluoride. 

Diff. — Distinguishing  characters  are  :  infusibility  ;  gelatinizing  with  acids ;  fluorine  reac- 
tion with  sulphuric  acid. 

Obs. — The  localities  of  the  crystallized  minerals  have  already  been  mentioned. 

The  granular  chondrodite  (?)  occurs  mostly  in  limestone.  It  is  found  in  Finland  and 
in  Sweden  ;  at  Taberg  in  Wermland  ;  at  Boden  in  Saxony  ;  on  Loch  Ness  in  Scotland  ;  at 
Achmatovsk  in  the  Ural,  etc.  Abundant  in  the  counties  of  Sussex,  N.  J. ,  and  Orange,  N.  Y., 
where  it  is  associated  with  spinel.  In  N.  Jersey,  at  Bryam  ;  at  Sparta;  at  Vernon,  Lockwood, 
and  Franklin.  'In  N.  York,  in  Orange  Co.,  in  Warwick,  Monroe,  etc.  ;  near  Edenville ;  at 
the  Tilly  Foster  Iron  Mine,  Brewster,  Putnam  Co.  In  Mass. ,  at  Chelmsford.  In  Penn. ,  near 
Chadsford.  In  Canada,  in  limestone  at  St.  Crosby  ;  St.  Jerome  ;  St.  Adele  ;  Grenville,  etc., 
abundant. 


Si02 

FeO 

MgO 

F 

I. 

Humite,  Vesuvius, 

35-63 

5-12 

54-45 

2-43 

II. 

Chondrodite,  Vesuvius, 

33-26 

2-30 

57-92 

5-04 

II. 

Chondrodite,  Brewster4 

34-10 

7-28 

53-72 

4-14 

II. 

Chondrodite,  Sweden, 

33-96 

6-83 

53-51 

4-24 

III. 

Clinolmmite,  Vesuvius, 

36-82 

5-48 

54-92 

2-40 

Chondrodite  (?),  K  Jersey, 

33-97 

3-48 

56-97 

7-44 

Rhombohedral.    j 
596  597 


TOURMALINE.    Turmalin,  Germ. 


=  103 


=:  0-89526.    iAj  = 
600 


Gouverneur,  N.  Y.  St.  Lawrence  Co. ,  N.Y. 

154°  59',  i  A  4  =  133°   8',  i-2  A  J5  =  155°  14',  *-2  A  ¥  =  142°  26'.     Usually 


308  DESCRIPTIVE   MINERALOGY. 

hemihedral,  being  often  unlike  at  the  opposite  extremities,  or  hemimorphic, 
and  the  prisms  often  triangular.  Cleavage :  11,  —\.  and  *-2,  difficult. 
Sometimes  massive  compact;  also  columnar,  coarse  or  fine,  parallel  or 
divergent. 

II.=7-7'5.  G.  =  2-94r-3'3.  Lustre  vitreous.  Color  black,  brownish- 
black,  bluish-black,  most  common  ;  blue,  green,  red,  and  sometimes  of  rich 
shades ;  rarely  white  or  colorless ;  some  specimens  red  internally  and  green 
externally ;  and  others  red  at  one  extremity,  and  green,  blue,  or  black  at 
the  other.  Dichroic  (p.  161).  Streak  uncolored.  Transparent — opaque  ; 
greater  transparency  across  the  prism  than  in  the  line  of  the  axis.  1  rac- 
ture  subconchoidal — uneven.  Brittle.  Pyroelectric  (p.  165). 

Var.— 1.  Ordinary.  In  crystals,  (a)  Rubellite  ;  the  red  sometimes  transparent,  (b)  Indi- 
colite  ;  the  blue,  either  pale  or  bluish -black  ;  named  from  the  indigo-blue  color,  (c)  Brazilian 
Sapphire  (in  jewelry);  Berlin-blue  and  transparent;  (d)  Brazilian  Emerald,  Chrysolite  (or 
Peridot)  of  Brazil ;  green  and  transparent,  (e)  Peridot  of  Ceylon  ;  honey-yellow.  (/)  Ack- 
roite ;  colorless  tourmaline,  from  Elba,  (g)  Aphrizite  ;  black  tourmaline,  from  Krageroe, 
Norway,  (h)  Columnar  and  black ;  coarse  columnar.  Resembles  somewhat  hornblende,  but 
has  a  more  resinous  fracture,  and  is  without  distinct  cleavage  or  anything  like  a  fibrous 
appearance  in  the  texture. 

Comp. — Q.  ratio  of  all  varieties  for  R  :  Si=3  :  2  (Rammelsberg),  conseqiiently  the  general 

n    i  i  ii 

formula  is  R3(R6,R)Si05.  R  may  represent  here  H,  K,  Na,  Li ;  also  R=Mg(Ca),Fe,Mn,  and 
R=:A:1,B2  ;  further  than  this  the  Si  is  often  in  part  replaced  by  F2.  Rammelsberg  distin- 
guishes two  groups,  where  the  Q.  ratio  for  B  :  Al  :  Si=3  :  0  :  8,  and  (2)  with  the  Q.  ratio  for 
B  :  Al  :  Si=l  :  3  :  3.  In  the  first  group  fall  most  of  the  yellow,  brown,  and  black  varieties, 

the  bivalent  elements  (Mg,Fe)  predominating,  the  general  formula  being  Rad^-R^Si.iOao. 
The  second  group  includes  the  colorless,  red,  and  slightly  green  kinds,  the  univalent  elements 

appearing  most  prominent,  especially  lithium.     The  general  formula  is  R6(R3)ftbSiuO46. 

Several  distinct  varieties  are  made  under  these  groups,  which  will  be  sufficiently  illustrated 
by  the  following  analyses,  by  Rammelsberg.  I.  Gouverneur,  brown-;  G.  =3*049.  II.  Haddam, 
black;  G.=3'136.  III.  Goshen,  blu ish- black ;  G.=3'203.  IV.  Paris,  Me.,  red;  G.=3'019. 
V.  Chesterfield,  Mass.,  green;  G.=3'069. 

Si02  B,03  A103  FeO  MnO  MgO  CaO  Na20  K2O  Li2O       F  H,O 

I.  38-85  (8-35)  31'32  1-14  1489  1'60  1-28  0-26 2-31=100-00 

II.   37-50  (9-02)  30-87  8 '54 8-60  1-33  1'60  0'73 —  1-81  =  100-00 

III.  36-22  10-65  33-35  11-95  1'25  0'63 1-75  0'40  0'84    0'82  2-21  =  100'82 

IV.  38-19  9-97  42-63 1-94  0-39  0-45  2'60  0'68  1-17     1-18  2'00=100'20 

V.    38-46  9-73  36-80  6-38  0'78  1'88  —  2 -47  0'47  0-72    0'55  2-31  =  100'55 

Fyr.,  etc. — I.  fuse  rather  easily  to  a  white  blebby  glass  or  slag ;  II.  fuse  with  a  strong  heat 
to  a  blebby  slag  or  enamel ;  III.  fuse  with  difficulty,  or,  in  some,  only  on  the  edges;  IV.  fuse 
on  the  edges,  and  often  with  great  difficulty,  and  some  are  infusible  ;  V.  infusible,  but  becom- 
ing white  or  paler.  With  the  fluxes  many  varieties  give  reactions  for  iron  and  manganese. 
Fused  with  a  mixture  of  potassium  bisulphate  and  fluorite  gives  a  strong  reaction  for  boracic 
acid.  By  heat  alone  tourmaline  loses  weight  from  the  evolution  of  silicon  fluoride  and  per- 
haps also  boron  fluoride ;  and  only  after  previous  ignition  is  the  mineral  completely  decom- 
posed by  fluohydric  acid.  Not  decomposed  by  acids  (Ramm. ).  After  fusion  perfectly  decom- 
posed by  sulphuric  acid  (v.  Kobell).  - 

Diff. — Distinguished  by  its  form,  occurring  commonly  in  three  sided,  or  six-sided  prisms; 
absence  of  cleavage  (unlike  hornblende).  It  is  less  easily  fusible  than  garnet  or  vesuvianite. 
B.B.  (see  below)  gives  a  green  flame  (boron). 

Obs. — Tourmaline  is  usually  found  in  granite,  gneiss,  syenite,  mica,  chloritic  or  talcose  schist, 
dolomite,  granular  limestone,  and  sometimes  in  sandstone  near  dykes  of  igneous  rocks.  The 
variety  in  granular  limestone  or  dolomite  is  commonly  brown. 

Prominent  localities  are  Katherinenburg  in  Siberia  ;  Elba  ;  Windisch  Kappell  in  Carinthia  ; 
Rozena;  Airolo,  Switzerland;  St.  Gothard.  In  Great  Britain.  Bovey  Tracey  in  Devon; 
Cornwall,  at  different  localities  ;  Aberdeen  in  Scotland,  etc. 

In  the  U.  States,  in  Maine,  at  Paris  and  Hebron.  In  Mass.,  at  Chesterfield ;  at  Goshen,  blue. 
In  N.  Hamp.,  Graf  ton  ;  Acworth,  etc.  In  Conn.,  at  Monroe  and  Haddam,  black.  In  N.  York, 


OXYGEN    COMPOUNDS ANHYDKOUS    SILICATES. 


309 


near  Gouverneur;  near  Port  Henry,  Essex  Co.,  enclosing  orthoclase  (see  p.  109) ;  Pierrepont; 
near  Edenville.  In  Penn. ,  near  Unionville ;  at  Chester  ;  Middletown,  and  elsewhere.  In 
Canada,  at  G-.  Calumet  Id.  ;  at  Fitzroy,  C.  W.  ;  at  Hunterstown,  C.  E. ;  at  Bathurst  and 
Elrasley,  C.  W. 


GrEiiLENiTE. — Tetragonal.  Color  grayish-green.  Q.  ratio  for  R  :  R  :  Si=3  :  3  :  4,  or  3  :  2 
for  bases  and  silicon.  Formula  Ca3RSi2Oio,  with  R=A1  :  Fe=5  :  1  ;  this  requires  Silica  29*9, 
alumina  21 '5,  iron  sesquioxide  6 -6.  lime  4 '20=100.  Mt.  Monzoni,  Fassathal,  Tyrol. 


ANDALUSITE. 


Orthorhombic.  /A  1=  90°  48',  O  A  14  =  144°  32' 
:  1*01405  :  1.  Cleavage  :  I  perfect  in  crystals  from 
Brazil ;  i-l  less  perfect ;  i-$  in  traces.  Massive,  im- 


l  :  a  =  0-71241 


Color  whitish,  rose-red,  flesh-red,  violet,  pearl-gray, 
reddish-brown,  olive-green.  Streak  un colored.  Trans- 
parent to  opaque,  usually  subtranslucent.  Fracture 
uneven,  subconchoidal. 

Var. — 1.  Ordinary.  H.  =--7'5  on  the  basal  face,  if  not  elsewhere. 
2.  Chiastolite  (made),  Sterling,  Mass.  Stout  crystals  having  the 
axis  and  angles  of  a  different  color  from  the  rest,  owing  to  a  regu- 
lar arrangement  of  impurities  through  the  interior,  and  hence  ex- 
hibiting a  colored  cross,  or  a  tesselated  appearance  in  a  transverse 
section.  H.=:3-7'5,  varying  much  with  the  degree  of  impurity. 
The  following  figure  shows  sections  of  some  crystals  (see  also  p.  110). 


2    " 

ZZ 

r    ; 
I 

1 

1 

j 

604 


Comp.— Q.  ratio  for  R  :  Si— 3  :  2  ;  AlSi05  =  Silica36'9,  alumina  63 '1=100.  Sometimes  a 
little  FeO3  is  present. 

Pyr.,  etc. — B.B.  infusible.  With  cobalt  solution  gives  a  blue  color.  Not  decomposed  by 
acids.  Decomposed  on  fusion  with  caustic  alkalies  and  alkaline  carbonates. 

Diff. — Distinguishing  characters:  infusibility  ;  hardness;  and  the  form,  being  nearly  that 
of  a  square  prism,  unlike  staurolite. 

Obs. — Most  common  in  argillaceous  schist,  or  other  schists  imperfectly  crystalline  ;  also  in 
gneiss,  mica  schist,  and  related  rocks.  Found  in  Spain,  in  Andalusia,  and  thence  the  name 
of  the  species  ;  in  the  Tyrol,  Lisens  valley  ;  in  Saxony,  at  Braunsdorf,  and  elsewhere.  In 
Ireland.  In  Brazil,  province  of  Minas  G-eraes  (transparent).  Common  in  crystalline  rocks  of 
Xew  England  and  Canada;  good  crystals  have  been  obtained  in  Delaware  Co.,  Penn.,  etc.; 
also  in  California;  in  Mass.,  at  Sterling  (chiastolite). 


FIBROLITE.     Bucholzite.     Sillimanite. 


Monoclinic.  /A  !•=.  96°  to  98°  in  the  smoothest  crystals  ;  usually  larger, 
the  faces  I  striated,  and  passing  into  i-Z.  Cleavage  :  i-l  very  perfect,  bril- 
liant. Crystals  commonly  long  and  slender.  Also  fibrous  or  columnar 
massive,  sometimes  radiating. 


310  DESCRIPTIVE  MINERALOGY. 

II.  — 6-7.  G.  =  3'2-3'3.  Lustre  vitreous,  approaching  subadamantine. 
Color  hair-brown,  grayish-brown,  grayish- white,  grayish-green,  pale  olive- 
green.  Streak  uncolored.  Transparent  to  translucent. 

Var. — 1.  Sillimanite  In  long-,  slender  crystals,  passing  into  fibrous,  with  the  fibres  separ- 
able. 2.  Fibrolite.  Fibrous  or  fine  columnar,  firm  and  compact,  sometimes  radiated  ;  gray- 
ish-white to  pale  brown,  and  pale  olive-green  or  greenish- gray.  Bucholzite  and  monrolite  are 
here  included  ;  the  latter  is  radiated  columnar,  and  of  the  greenish  color  mentioned. 

Comp AHSi05,  as  for  andalusite^  Silica  86 '9,  alumina  631  =  100. 

Pyr.j  etc — Same  as  given  under  andalusite. 

Diff. — Distinguished  from  tremolite  by  its  infusibility  ;  also  by  its  brilliant  diagonal  cleav- 
age, in  which  and  in  its  specific  gravity  it  differs  from  cyanite. 

Obs. — Occurs  in  gneiss,  mica  schist,  and  related  metamorphic  rocks.  In  the  Fassathal, 
Tyrol  (buchokite}  ;  at  Bodenmais  in  Bavaria,  etc.  In  the  United  States,  at  Worcester,  Mass. 
Near  Norwich,  Conn.  ;  at  Chester,  near  Saybrook  (sillimatiite).  In  N.  York,  in  Monroe, 
Orange  Co.  (monrolite).  In  Penn.,  at  Chester  on  the  Delaware;  in  Delaware  Co.,  etc.  In 
Delaware,  at  Brandywine  Springs.  In  N.  Carolina,  with  corundum. 

Fibrolite  was  much  used  for  stone  implements  in  western  Eurooe  in  the  u  Stone  age." 

WORTIIITE,  a  hydrous  fibrolite  ;  WESTANITE  (Sweden)  is  related  in  composition. 


CYANITE.     Kyanite.     Disthene. 

Triclinic.  In  flattened  prisms  ;  O  rarely  observed.  Crystals  oblong, 
usually  very  long  and  blade-like.  Cleavage  :  i-l  distinct ;  i-i  less  so ;  O 
imperfect.  Also  coarsely  bladed  columnar  to  subfibrous. 

H.  =  5-7'25,  the  least  on  the  lateral  planes.  G.  =  3-45-3'7.  Lustre  vit- 
reous— pearly.  Color  blue,  white,  blue  along  the  centre  of  the  blades  or 
crystals  with  white  margins ;  also  gray,  green,  black.  Streak  uncolored. 
Translucent — transparent. 

Var. — The  white  cyanite  is  sometimes  called  Rhoetwte. 

Comp, — AlSiO  5  =  Silica  36'9,  alumina  63'1  =  100,  like  andalusite  and  fibrolite. 
•    Pyr.,  etc. — Same  as  for  andalusite. 

Diff. — Unlike  the  amphibole  group  of  minerals  in  its  infusibility  ;  occurrence  in  thin-bladed 
prisms  characteristic. 

Obs. — Occurs  principally  in  gneiss  and  mica  slate.  Found  at  St.  Gothard  in  Switzerland  ; 
at  Greiner  and  Pfitsch  in  the  Tyrol;  also  in  Styria  ;  Carinthia  ;  Bohemia.  In  Mass.,  at 
Chesterfield,  etc.  In  Conn.,  at  Litchfield;  at  Oxford.  In  Vermont ,  at  Thetford. 
in  Chester  Co. ;  and  Delaware  Co.  In  N.  Carolina. 


TOPAZ. 

Orthorhombic.  /A  /  =  124°  17',  O  A  l-i  =  138°  3' ;  c  :  I  :  a  =0-90243 
:  1-8920  :  1.  O  A  1  =  134°  25',  1  A  1,  inacr.,  =  141°  0'.  Crystals  usually 
hemihedral,  the  extremities  being  unlike  ;  habit  prismatic.  Cleavage : 
basal,  highly  perfect.  Also  firm  columnar  ;  also  granular,  coarse  or  fine. 

H.:=:8.  Gr.^3-4-3'65.  Lustre  vitreous.  Color  straw-yellow,  wine- 
yellow,  white,  grayish,  greenish,  bluish,  reddish  ;  pale.  Streak  uncolored. 
Transparent — subtranslucent.  Fracture  subconchoidal,  uneven.  Pyro- 


OXYGEN   COMPOUNDS — ANHYDROUS   SILICATES. 


311 


electric.  Optic-axial  plane  i-l ;  divergence  very  variable,  sometimes  differ- 
•ing  much  in  different  parts  of  the  same  crystal ;  bisectrix  positive,  normal 
to  O. 


609 


Trumbull,  Ct. 


S  chneckenstein. 


Oomp. — AlSi05,  with  part  of  the  oxygen  replaced  by  fluorine  (F2)  ;  ratio  of  F2  :  O  =  l  :  5= 
Silicon  15-17,  aluminum  29'58,  oxygen  34*67,  fluorine  20-58=100. 

Pyr.,  etc. — B.B.  infusible.  Some  varieties  take  a  wine-yellow  or  pink  tinge  when  heated. 
Fused  in  the  open  tube  with  salt  of  phosphorus  gives  the  reaction  for  fluorine.  With  cobalt 
solution  the  pulverized  mineral  gives  a  fine  blue  on  heating.  Only  partially  attacked  by  sul- 
phuric acid. 

Diff. — Distinguishing  characters: — hardness,  greater  than  that  of  quartz;  infusibility  ; 
perfect  basal  cleavage.  B.B.  yields  fluorine. 

Obs. — Topaz  occurs  in  gneiss  or  granite,  with  tourmaline,  mica,  and  beryl,  occasionally 
with  apatite,  fluorite,  and  tin  ore  ;  also  in  talcose  rock,  as  in  Brazil,  with  euclase,  etc.,  or 
in  mica  slate.  Fine  topazes  come  from  the  Urals  ;  Kamschatka  ;  Brazil ;  in  Cairngorm, 
Aberdeenshire  ;  at  the  tin  mines  of  Bohemia  and  Saxony.  Physalite  (a  coarse  variety),  occurs 
at  Fossum,  Norway  ;  also  in  Durango,  Mexico ;  at  La  Paz,  province  of  Guanaxuato.  In  the 
United  States,  in  Conn.,  at  Trumbull.  In  2f.  Car.,  at  Crowder's  Mountain.  In  Utah,  in 
Thomas's  Mts.  ;  from  gold  washings  of  Oregon. 


EUCLASE. 

Monoclinic.     O  =  T9°  44'=  0  A  i-i,  I A  1=  115°  0',  O  A 14  =  146°  45' 
c  :  I :  d  =  1-02943  :  1-5446  :  1  =  1  :  1-50043  :  0-97135. 
Cleavage:  i4  very  perfect  and  brilliant;   O,  i-i  much 
less  distinct.     Found  only  in  crystals. 

H.  =  7-5.  G.  =3-098  (Haid.)/  Lustre  vitreous,  some- 
what pearly  on  the  cleavage-face.  Colorless,  pale  moun- 
tain-green, passing  into  blue  and  white.  Streak  un- 
colored.  Transparent ;  occasionally  subtransparent. 
Fracture  conchoidal.  Very  brittle. 

Comp.— Q.  ratio  for  H  :  Be  :  Al  :  Si=l  :  2  :  3  :  4,  forR  :  Si=3  :  2 
(H2=R,  and  3R=A1),  formula,  H2Be2AlSi2Oi0=Silica  41/20,  alumina 
35-22,  glucina  17 '39,  water  619= 100. 

Pyr.,  etc. — In  the  closed  tube,  when  strongly  ignited,  B.B.  gives  off 
water  (Damour).  B.B.  in  the  forceps  cracks  and  whitens,  throws  out 
points,  and  fuses  at  5  '5  to  a  white  enamel.  Not  acted  on  by  acids. 

Obs. — Occurs  in  Brazil,  at  Villa  Rica ;  in  southern  Ural,  near  the  r  ver  Sanarka. 


312 


DESCRIPTIVE   MINEEALOGY. 


DATOLITB.    Humboldtite. 

Monoclimc.  C  =  89°  54/=  O  (below)  A  i-i,  I/\l=  115°  3',  O  A  1-i  = 
162°  27' ;  c  :  I  :  d  =  0-49695  :  1-5712  :  1.  0  A  -  2-*  =  135°  13',  0  A  1  = 
149°  33',  /A  /front  =  115°  3',  24  A  24,  ov.  0,  =  115°  21',  f£  A  t-fc,  ov.  £*, 
=  76°  18',  44  A  44,  ov.  0,  =  76°  88.  Cleavage  :  O  distinct.  Also  botry- 
oidal  and  globular,  having  a  columnar  structure  ;  also  divergent  and  radi- 
ating ;  also  massive,  granular  to  compact. 


612 


613 


614 


Bergen  Hill. 


Bergen  Hill. 


Arendal. 


H.  =  5-5-5.  G.  =  2-8-3;  2'989,  Arendal,  Ilaidinger.  Lustre  vitreous, 
rarely  subresinous  on  a  surface  of  fracture  ;  color  white ;  sometimes  gray- 
ish, pale-green,  yellow,  red,  or  amethystine,  rarely  dirty  olive-green  or 
honey-yellow.  Streak  white.  Translucent;  rarely  opaque  white.  Frac- 
ture uneven,  subconchoidal.  Brittle.  Plane  of  optic-axes  i-l;  angle  of 
divergence  very  obtuse  ;  bisectrix  makes  an  angle  of  4°  with  a  normal  to  i-i. 

Var. — 1.  Ordinary.     In  crystals,  glassy  in  aspect.     Usual  forms  as  in  figures.     2.  Compact 


OXYGEN    COMPOUNDS ANHYDROUS    SILICATES. 


313 


massive.  White  opaque,  breaking-  with  the  surface  of  porcelain  or  Wedgewood  ware.  From 
the  L.  Superior  region.  3.  Botryoidal ;  Botryoliie.  Radiated  columnar,  having  a  botryoidal 
surface,  and  containing  more  water  than  the  crystals.  The  original  locality  of  both  the  crys- 
tallized and  botryoidal  was  Arendal,  Norway.  Haytorite  is  datolite  altered  to  chalcedony, 
from  the  Haytor  Iron  Mine,  England. 

Comp  — Q.  ratio  for  H  :  Ca  :  B  :  Si=l  :  2  :  3  :  4,  like  euclase:  formula  H2Ca2B2Si2010= 
Silica  37 *5,  boron  trioxide  21-9,  lime  35 '0,  water  5 '6 =100.  Botryolite  contains  10 '64  p.c.  water. 

Pyr.,  etc. — In  the  closed  tube  gives  off  much  water.  B.B.  fuses  at  2  with  intumescence  to 
a  clear  glass,  coloring  the  flame  bright  green.  Gelatinizes  with  hydrochloric  acid. 

Diff, — Distinguishing  characters:  glassy  lustre;  usually  complex  crystallization;  B.B. 
fuses  easily  with  a  green  flame  ;  gelatinizes  with  acids. 

Obs. — Datolite  is  found  in  trappean  rocks  ;  also  in  gneiss,  dioryte,  and  serpentine  ;  in  me- 
tallic veins  ;  sometimes  also  in  beds  of  iron  ore.  Found  hi  Scotland  ;  at  Arendal ;  at  Andreas- 
berg  ;  at  Baveno  near  Lago  Maggiore  ;  at  the  Seisser  Alp,  Tyrol ;  at  Toggiana  in  Modena,  in 
serpentine.  In  good  specimens  at  Roaring  Brook,  near  New  Haven ;  also  at  many  other 
localities  in  the  trap  rocks  of  Connecticut ;  in  N.  Jersey,  at  Bergen  Hill  ;  in  the  Lake  Superior 
region,  and  on  Isle  Royale.  Santa  Clara,  Cal. ,  with  garnet  and  vesuvianite. 


TITANITE.    SPHENE. 


Monoclinic.  C  =  60°  17'  =  0  A  i-i  ;  /A  1=  113°  31',  O  A  14  =  159° 
39' ;  c  :  b  :  d  =  0-56586  :  1-3251  :  1.  Cleavage :  I  sometimes  nearly  per- 
fect ;  i-i  and  —1  much  less  so  ;  rarely  (in  greenovite)  2  easy,  —2  less  so  ; 
sometimes  hemimorphic.  Twins  :  twinning-plane  i-i  ;  usually  producing 
thin  tables  with  a  reentering  angle  along  one  side  ;  sometimes  elongated, 
as  in  f.  623.  Sometimes  massive,  compact ;  rarely  lamellar. 


619 


620 


621 


Lederite. 


Spinthere.         Schwarzenstein. 

H.=5-5'5.     G.=3'4—  3-56.     Lustre  adamantine — resinous.    Color  brown, 
gray,  yellow,  green,  and  black.     Streak  white,  slightly  reddish  in  greenovite. 


314 


DESCRIPTIVE   MINERALOGY. 


Transparent — opaque.  Brittle.  Optic-axial  plane  i-\  ;  bisectrix  positive, 
very  closely  normal  to  \-i  (x) ;  double  refraction  strong  ;  axial  divergence 
53°-56°  for  the  red  rays,  46°-45°  for  the  blue  ;  DesCl.  ' 

Oomp.,  Var.— Q.  ratio  for  Ca  :  Ti  :  Si=l  :  2  :  2,  or  making  the  Ti  basic  (Ti=2R),  R  :  Si 
=3:2;  formula  (equivalent  to  RSi05)  CaTiSi06= Silica  30'61,  titanic  oxide  40*82,  lime  28 -57 
=100. 

Var. —  Ordinary,  (a)  Titanite  ;  brown  to  black,  the  original  being  thus  colored,  also  opaque 
or  sub  translucent,  (b)  Sphene  (named  from  afyfy,  a  wedge,}  ;  of  light  shades,  as  yellow,  green- 
ish, etc. ,  and  often  translucent ;  the  original  was  yellow.  Manganesian  ;  Greenomte.  Red 
or  rose-colored,  owing  to  the  presence  of  a  little  manganese.  In  the  crystals  there  is  a  great 
diversity  of  form,  arising  from  an  elongation  or  not  into  a  prism,  and  from  the  occurrence  of 
the  elongation  in  the  direction  of  different  diameters  of  the  fundamental  form. 

Pyr.,  etc. — B.B.  some  varieties  change  color,  becoming  yellow,  and  fuse  at  3  with  intu- 
mescence, to  a  yellow,  brown,  or  black  glass.  With  borax  they  afford  a  clear  yellowish-green 
glass.  Imperfectly  soluble  in  heated  hydrochloric  acid ;  and  if  the  solution  be  concentrated 
along  with  tin,  it  becomes  of  a  fine  violet  color.  With  salt  of  phosphorus  in  R.F.  gives  a 
violet  bead  ;  varieties  containing  much  iron  require  to  be  treated  with  the  flux  on  charcoal 
with  metallic  tin.  Completely  decomposed  by  sulphuric  and  fluohydric  acids. 

Diff. — The  resinous  lustre  is  very  characteristic  ;  and  its  commonly  occurring  wedge-shaped 
form.  B.B.  gives  a  titanium  reaction. 

Obs. — Titanite  occurs  in  imbedded  crystals,  in  granite,  gneiss,  mica  schist,  syenite,  chlorite 
schist,  and  granular  limestone  ;  also  in  beds  of  iron  ore,  and  volcanic  rocks,  and  often  asso- 
ciated with  pyroxene,  hornblende,  chlorite,  scapolite,  zircon,  etc.  Found  at  St.  Gothard,  and 
elsewhere  in  the  Alps;  in  the  protogine  of  Chamouni  (pictite,  Saus.);  at  Ala,  Piedmont 
(ligurile) ;  at  Arendal,  in  Norway  ;  at  Achmatovsk,  Urals ;  at  St.  Marcel  in  Piedmont  (gretin- 
omte,  Duf .) ;  at  Schwarzenstein,  Tyrol ;  in  the  Untersulzbachthal  in  Pinzgau  ;  near  Tavistock ; 
near  Tremadoc,  in  North  Wales. 

Occurs  in  Canada,  at  Grenville,  Elmsley ,  etc.  In  Maine,  at  Sanf ord.  In  Mass. ,  at  Bol- 
ton  ;  at  Pelham.  In  N.  York,  at  Gouverneur  ;  at  Diana,  in  dark-brown  crystals  (lederite) ; 
in  Orange  Co. ;  near  Edenville  ;  near  Warwick.  In  N.  Jersey,  at  Franklin.  In  Penn. ,  Bucks 
Co. ,  near  Attleboro'. 

GUAEINITE. — Same  composition  as  titanite,  but  orthorhombic  (v.  Lang  and  Guiscardi)  in 
crystallization.  Color  yellow.  Mt.  Somma. 

KEILHAUITE  (Yttro titanite). — Near  sphene  in  form  and  composition,  but  containing  alu- 
mina and  yttria.  Arendal,  Norway. 

TSCHEFFKINITE.— Analogous  to  keilhauite  in  composition,  containing,  besides  titanium, 
also  cerium  (La,Di).  Occurs  massive.  Ilmen  Mts. 


STAUROLITE. 


Orthorhombic.    /A  1=  129°  20',  O  A  \-i  =  124°  46' ;  c  :  I :  a  =  1-M06 
2-11233  :  1.     Cleavage  :  i-l  distinct,  but  interrupted ;  J  in  traces.     Twins 

630 


627 


cruciform:  twinning-plane  i-\  (f.  628) ;  \4  (f.  629);  and  f-f  (f.  630).    Fig. 


OXYGEN    COMPOUNDS HYDKOUS    SILICATES. 


315 


631  is  a  drilling  according  to  the  last  method  of  twinning,  and  in  f.  632  both 
methods  are  combined.     See  also 

631  632 


p.  90  and  p.  98.      Crystals  often 
rou 


p. 

with    rough    surfaces.       Massive 
forms  unobserved. 

II.  =  7-7'5.  G.  =  3-4r-3-8.  Sab- 
vitreous,  inclining  to  resinous. 
Color  dark  reddish-brown  to 
brownish-black,  and  yellowish- 
brown.  Streak  nncolored  to 
grayish.  Translucent  —  nearly  or 
quite  opaque.  Fracture  conchoidal. 

Comp.,  Var.—  Q.  ratio,  according-  to  Ramrnelsberg,  f  or  R  :  ft  :  Si=2  :  9  :  6  (where  Ris  Fe 
and  Mg,  and  also  includes  H2,  with  H2  :  R=l  :  3).  Formula  H,R,Al,Pi9O84  (if  Mg  :  Fe=l  :  3) 
=  Silica  30*37,  alumina  51  '92,  iron  protoxide  13  '66,  magnesia  2  "53,  water  1*52=100.  The 
iron  was  first  taken  as  FeO3,  but  Mitscherlich  showed  that  it  was  really  FeO.  Staurolite 
often  includes  impurities,  especially  free  quartz,  as  first  shown  by  Lechartier,  and  since  then 
by  Fischer,  Lasaulx,  and  Rammelsberg.  This  is  the  cause  of  the  variation  in  the  amount  of 
silica  appearing  in  most  analyses,  there  being  sometimes  as  much  as  50  p.  c. 

Pyr.,  etc  __  B.B.  infusible,  excepting  the  magnesian  variety,  which  fuses  easily  to  a  black 
magnetic  glass.  With  the  fluxes  gives  reactions  for  iron,  and  sometimes  for  manganese. 
Imperfectly  decomposed  by  sulphuric  acid. 

Diff.  —  Always  in  crystals  ;  the  prisms  obtuse,  having  an  angle  of  129°. 

Obs.  —  Usually  found  in  mica  schist,  argillaceous  schist,  and  gneiss  ;  often  associated  with 
garneb,  cyanite,  and  tourmaline.  Occurs  with  cyanite  in  paragonite  schist,  at  Mt.  Campione, 
Switzerland  ;  at  the  G-reiner  mountain,  and  elsewhere  in  the  Tyrol  ;  in  Brittany  ;  in  Ireland. 
Abundant  throughout  the  mica  slate  of  New  England.  In  Maine,  at  Windham,  and  elsewhere. 
In  Mass.,  at  Chesterfield,  etc.  In  Penn.  In  Georgia,  at  Canton  ;  and  in  Fannin  Co. 

SCIIORLOMITK.  —  Q.  ratio  for  Ca+Fe-t-Ti  :  Si=2  :  1,  nearly.  Analysis  by  Ramm.,  Arkan- 
sas, SiO2  26-09,  Ti02  21^4,  Fe03  20'11,  FeO  1'57,  CaO  29'38,  MgO  1  -36=99-85.  Color  black. 
Fracture  conchoidal.  Magnet  Cove,  Arkansas  ;  Kaiser  stuhlgebirge  in  Breisgau. 


HYDBOUS    SILICATES. 
I.  GENERAL  SECTION.     A.  BISILICATES. 


PECTOLITE. 

Monoclinic,  isomorphous  with  wollastonite,  Greg.  Cleavage  :  i-i  (orthod.) 
perfect.  Twins  :  twinning-plane  i-i.  Usually  in  close  aggregations  of  aci- 
cular  crystals.  Fibrous  massive,  radiated  to  stellate. 

H.=5.  G.  =  2-68-2'78.  Lustre  of  the  surface  of  fracture  silky  or  sub- 
vitreous.  Color  whitish  or  grayish.  Subtranslucent  to  opaque.  Tough. 
For  Bergen  mineral  optic-axial  plane  parallel  to  orthodiagonal,  and  very 
nearly  normal  to  i-i  ;  acute  bisectrix  positive,  parallel  to  orthodiagonal,  and 
obtuse  bisectrix  nearly  normal  to  cleavage-plane  or  i-i ;  axial  angle  in  oil, 
through  cleavage-plates,  143°-145° ;  DesCl. 

Var. — Almost  always  columnar  or  fibrous,  and  divergent,  the  fibres  often  2  or  3  inches  long, 
and  sometimes,  as  in  Ayrshire,  Scotland,  a  yard.  Resembles  in  aspect  fibrous  varieties  of 
natrolite,  okenite,  thomsonite,  tremolite,  and  wollastonite. 


316 


DESCRIPTIVE   MINERALOGY. 


Comp.— Q.  ratio  for  H  :  Na  :  Ca  :  Si=l  :  1  :  4  :  12,  and  for  R  :  Si  (where  R  includes  Ca, 
and  H2sNa2):=l  :  2,  like  wollastonite ;  hence  formula  HNaCa2Si3O9  =  Silica  54  P2,  lime  33'8, 
soda  9 '3,  water  2*7=100.  If  the  H  does  not  belong  with  the  bases,  then  the  formula  may  be 
(Ramm.)  Na2Ca4Si6On+aq. 

Pyr.,  etc. — In  the  closed  tube  yields  water.  B.  B.  fuses  at  2  to  a  white  enamel.  Gela- 
tinizes with  hydrochloric  acid.  Often  gives  out  a  light  when  broken  in  the  dark. 

Obs. — Occurs  mostly  in  trap  and  related  rocks,  in  cavities  or  seams  ;  occasionally  in  meta- 
morphic  rocks.  Found  in  Scotland,  near  Edinburgh;  in  Ayrshire;  and  at  Taliver,  etc.,  I. 
Skye ;  at  Mt.  Baldo  and  Mt.  Monzoni  in  the  Tyrol ;  in  Wermland  ;  at  Bergen  Hill,  N.  J. ; 
compact  at  Isle  Roy  ale,  L.  Superior. 


Monoclinic. 


inclining 


LAUMONTITE.     Caporcianite. 

C=  68°  40',  /A  7  =86°  16',  O  A  14  =  151°  9' ;  c  :  I  :  d  = 
0-516  :  OS727  :  1.  Prism  with  very  oblique  terminal  plane 
2-a,  the  most  common  form.  Cleavage  :  i-\  and  7 perfect ; 
i-i  imperfect.  Twins  :  twinning-plane  i-i.  Also  columnar, 
radiating  or  divergent. 

II.=3-5-4.  G.  =  2-25-2-36.  Lustre  vitreous, 
to  pearly  upon  the  faces  of  cleavage.  Color  white,  passing 
into  yellow  or  gray,  sometimes  red.  Streak  uncolored. 
Transparent — translucent;  becoming  opaque  and  usually 
pulverulent  on  exposure.  Fracture  scarcely  observable, 
uneven.  Not  very  brittle.  Double  refraction  weak  ;  optic- 
axial  plane  i-\\  divergence  52°  24'  for  the  red  rays;  bisec- 
trix negative,  making  an  angle  of  20°  to  25°  with  a  normal 
to  i-i ;  DesCl. 

Comp Q.  ratio  f or  R  :  R  :  Si  :  H^l  :  3  :  8  :  4 ;  and  R  :  Si=l  :  2  (3R=R).  R=Ca,  B 

=Al,  and  the  formula  is  hence  CaMSi4Oi2+4aq— Silica  50'0,  alumina  21 '8,  lime  11*9,  water 
16-3=100. 

Pyr.,  etc. — Loses  part  of  its  water  over  sulphuric  acid,  but  a  red  heat  is  needed  to  drive 
off  all.  B.B.  swells  up  and  fuses  at  2 '7-3  to  a  white  enamel.  G-elatinizes  with  hydrochloric 
acid. 

Obs. — Laumontite  occurs  in  the  cavities  of  trap  or  amygdaloid  ;  also  in  porphyry  and  sye- 
nite, and  occasionally  in  veins  traversing  clay  slate  with  calcite.  Its  principal  localities  are 
at  the  Faroe  Islands  ;  Disko  in  Greenland  ;  in  Bohemia,  at  Eule  ;  St.  Gothard  in  Switzer- 
land ;  the  Fassathal ;  the  Kilpatrick  hills,  near  Glasgow.  Nova  Scotia  affords  fine  specimens  ; 
also  Lake  Superior,  in  the  copper  region,  and  on  I.  Royale ;  also  Bergen  Hill,  N.  J. 

OKENITE. — Formula  H^CaSisOe  +  aq,  having  half  the  water  basic  — Silica  56 '6,  lime  26  '4, 
water  17 '0=1 00.  Commonly  fibrous.  Color  white,  Faroe  Is.;  Disco,  Greenland;  Iceland. 

GYROLITE. — Occurs  in  radiated  concretions  at  the  Isle  of  Skye;  Nova  Scotia.  Formula 
perhaps  H^CaaSisOg+aq.  CENTRALLASSITE.  Related  to  okenite,  but  contains  1  molecule 
more  water.  In  trap  of  Nova  Scotia. 


CHRYSOCOLLA.    Kieselkupfer,  Germ. 

Cryptocrystalline ;  often  opal-like  or  enamel-like  in  texture ;  earthy. 
Incrusting,  or  filling  seams.  Sometimes  botryoidal. 

H.  — 2-4.  G-.  —  2-2*238.  Lustre  vitreous,  shining,  earthy.  Color  moun- 
tain-green, bluish-green,  passing  into  sky-blue  and  turquois-blue ;  brown  to 
black  when  impure.  Streak,  when  pure,  white.  Translucent — opaque. 
Fracture  conchoidal.  Rather  sectile  ;  translucent  varieties  brittle. 


OXYGEN    COMPOUNDS HYDROUS    SILICATES. 


317 


Comp. — Composition  varies  much  through  impurities,  as  with  other  amorphous  substances, 
resulting  from  alteration.  As  the  silica  has  been  derived  from  the  decomposition  of  other 
silicates,  it  is  natural  that  an  excess  should  appear  in  many  analyses.  True  chrysocolla  cor- 
responds to  the  Q.  ratio  for  Cu  :  Si  :  H,  1:2:  2=CuSiO3  +  2aq=r Silica  34-2,  copper  oxide 
45 '3,  water  20  "5  — 100.  But  some  analyses  afford  1:2:  3,  and  1:2:4.  Impure  chrysocolla 
may  contain,  besides  free  silica,  various  other  impurities,  the  color  varying  from  bluish-green 
to  brown  and  black,  the  last  especially  when  manganese  or  copper  is  present. 

Pyr.,  etc, — In  the  closed  tube  blackens  and  yields  water.  B.B.  decrepitates,  colors  the 
flame  emerald-green,  but  is  infusible.  With  the  fluxes  gives  the  reactions  for  copper.  With 
soda  and  charcoal  a  globule  of  metallic  copper.  Decomposed  by  acids  without  gelatinization. 

Diff. — Color  more  bluish-green  than  that  of  malachite,  and  it  does  not  effervesce  with 
acids. 

Obs. — Accompanies  other  copper  ores,  occurring  especially  in  the  upper  part  of  veins. 
Found  in  most  copper  mines  in  Cornwall ;  at  Libethen  in  Hungary ;  at  Falkenstein  and 
Schwatz  in  the  Tyrol ;  in  Siberia ;  the  Baunat ;  Thuringia ;  Schneeberg,  Saxony ;  Kupfer- 
berg,  Bavaria;  South  Australia  ;  Chili,  etc.  In  Somerville  and  Schuyler's  mines,  New  Jersey  ; 
at  Morgantown,  Pa.  ;  at  Cornwall,  Lebanon  Co.  ;  Nova  Scotia,  at  the  Basin  of  Mines ;  also 
in  Wisconsin  and  Michigan. 

DEMIDOFFITE  ;  CYANOCHALCITE  ;  RESANITE  ;  near  chrysocolla. 

C AT APLEIITE.— Analysis  (Ramm.),  SiO2  39'78,  ZrO2  40-12,  CaO  3 '45,  Na2O  7-59,  H2O  9*24 
=  100 '18.  Hexagonal.  Color  yellowish-brown,  Lamoe,  near  Brevig,  Norway. 


B.  UNISILICATES. 


CALAMINE.     Galmei;    Kieselzinkerz,  Germ. 


Orthorhombic  ;    hemimorphic-hemihedral.     7" A  1=  104:° 
148°  31',  Daubar ;   c  :  I  :  a  =  0  6124  :  1-2850  :  1.     Cleav- 
age :    7,  perfect ;   O,  in  traces.     Also  stalactitic,  mammil- 
lated,  botryoidal,  and   fibrous   forms;    also   massive  and 
granular. 

H.  =  4:-5-5,  the  latter  when  crystallized.  G.  =  3'16-3'9. 
Lustre  vitreous,  O  subpearly,  sometimes  adamantine.  Color 
white ;  sometimes  with  a  delicate  bluish  or  greenish  shade ; 
also  yellowish  to  brown.  Streak  white.  "Transparent — 
translucent.  Fracture  uneven.  Brittle.  Pyroelectric. 

Comp.— Q.  ratio  for  R  :  Si  :  H=l  :!:•£;  Zn2Si04+aq= Silica  25  0, 
zinc  oxide  67 '5,  water  7 -5  =  100. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  whitens,  and  gives  off 
water.  B.B.  almost  infusible  (F.=6);  moistened  with  cobalt  solution 

gives  a  green  color  when  heated.  On  charcoal  with  soda  gives  a  coating  which  is  yellow  while 
hot,  and  white  on  cooling.  Moistened  with  cobalt  solution,  and  heated  in  O.F.,  this  coating 
assumes  a  bright  green  color.  Gelatinizes  with  acids  even  when  previously  ignited.  Decora- 
posed  by  acetic  acid  with  gelatinization.  Soluble  in  a  strong  solution  of  caustic  potash. 

Diff. — Distinguishing  characters:   gelatinizing  with  acids;   inf  usibility  ;  reaction  for  zinc. 

Obs. — Calamine  and  smithsonite  are  usually  found  associated  in  veins  or  beds  in  stratified 
calcareous  rocks  accompanying  blende,  ores  of  iron,  and  lead,  as  at  Aix  la  Chapelle ;  Bleiberg 
in  Carinthia  ;  Retzbanya  ;  Schemnitz.  At  Roughten  Gill  in  Cumberland  ;  at  Alston  Moor ; 
near  Matlock  in  Derbyshire  ;  at  Castleton  ;  Leadhills,  Scotland. 

In  the  United  States  occurs  with  smithsonite  in  Jefferson  county,  Missouri.  At  Stirling 
Hill,  N.  J.  In  Pennsylvania,  at  the  Perkiomen  and  Phenixville  lead  mines ;  at  Bethlehem ; 
at  Friedensville.  Abundant  in  Virginia,  at  Austin's  mines. 


318 


DESCRIPTIVE   MINERALOGY. 


PREHNITE. 

Orthorliombic.  7  A  7=  99°  56',  O  A  14  =  146°  11 J' ;  c  :  J>  :  a  =  0-66963 
:  1-19035  :  1.  Cleavage:  basal,  distinct.  Tabular  crystals  often  united  by 
O,  making  broken  forms,  often  barrel-shaped.  Usually  reniform,  globular, 
and  stalactitic  with  a  crystalline  surface.  Structure  imperfectly  columnar 
or  lamellar,  strongly  coherent ;  also  compact  granular  or  impalpable. 

H.r=6-6:5.  G.  =  2-8-2-953.  Lustre  vitreous;  O  weak  pearly.  Color 
light  green,  oil-green,  passing  into  white  and  gray  ;  often  fading  on  expo- 
sure. Subtransparent — translucent ;  streak  uncolored.  Fracture  uneven. 
Somewhat  brittle. 

Comp. — Q.  ratio  for  R:R:Si:H=2:3:6:l,  whence,  if  the  water  is  basic,  for  bases 
and  silicon,  1:1;  formula  HsC».>AJSiaOri  or  Ca^lSi3Oii+aq= Silica  43'6,  alumina  24-9, 
lime  27-1,  water  4*4=100. 

Pyr.,  etc. — In  the  closed  tube  yields  water.  B.B.  fuses  at  2  with  intumescence  to  a  blebby 
enamel-like  glafs.  Decomposed  by  hydrochloric  acid  without  gelatinizing.  L'oupliolite,  which 
often  contains  dust  or  vegetable  matter,  blackens  and  emits  a  burnt  odor. 

Diff. — B.B.  fuses  readily,  unlike  beryl  and  chalcedony.  Its  hardness  is  greater  than  that  of 
the  zeolites. 

Obs — Occurs  in  granite,  gneiss,  syenite,  dioryte,  and  trappean  rocks  especially  the  last. 
At  Bourg  d'Oisans  in  Isere ;  in  the  Fassathal,  Tyrol ;  Ala  in  Piedmont ;  Joachimsthal  in 
Bohemia  ;  near  Andreasberg ;  Arendal,  Norway  ;  ^Edelfors  in  Sweden ;  in  Dumbartonshire  ; 
in  Renfrewshire. 

In  the  United  States,  in  Connecticut ;  Bergen  Hill,  N.  J. ;  on  north  shore  of  Lake  Superior  ; 
in  large  veins  in  the  Lake  Superior  copper  region. 

CHLORASTHOLITE  and  ZONOCHLORITE  from  Lake  Superior  are  mixtures,  as  shown  by 
Hawes. 

VILLARSITE. — Probably  an  altered  chrysolite.  Formula  R2SiO4+iaq  (or  ia(l)  R=Mg  :  Fe 
=11  :  1.  Traversella. 

CERITE,  Sweden,  and  TRITOMITE,  Norway,  contain  cerium,  lanthanum,  and  didymium. 
THORITE  and  ORANGITE  contain  thorium  Norway. 

PARATHORITE. — In  minute  orthorhombic  crystals,  imbedded  in  danburite  at  Danbury,  Ct.' 
Chemical  nature  unknown. 

PYROSMALITE.— Analysis  by  Ludwig,  Si02  34'66,  FeO  27-05,  MnO  25-60,  CaO  0-52,  MgO 
0'93,  H20  8-31,  Cl  4'88=10l-85>  In  hexagonal  tables.  Color  blackish-green.  Nya-Koppar- 
berg,  etc.,  Sweden. 

APOPHYLLITE. 


Tetragonal. 


635 


red.     Streak  uncolored. 


0  A  l-i  =  128°  38';  c  =  1'2515.     Crystals  sometimes  nearly 

cylindrical  or  barrel- 
shaped.  Twin's  :  twin- 
ning-plane  the  octahe- 
dron 1.  Cleavage :  O 
highly  perfect;  /  less 
so.  Also  massive  and 
lamellar. 

H.=4-5-5.  G.^2-3- 
2'4.  Lustre  of  O  pearly; 
of  the  other  faces  vitre- 
ous. Color  white,  or 
grayish ;  occasionally 
with  a  greenish,  yellow- 
ish, or  rose-red  tint,  flesh- 
Transparent  ;  rarely  opaque.  Brittle. 


v 


OXYGEN   COMPOUNDS — HYDROUS    SILICATES.  319 

Oomp. — Q.  ratio  for  R  :  Si  :  H  usually  taken  as  1  :  4  :  2,  part  of  the  oxygen  replaced  by 
fluorine  (F2).  According  to  Kammelsberg  the  ratio  is  9  :  82  :  16;  he  writes  the  formula 
4(HoCaSijO6+aq)+KF.  This  requires:  Silica  52 '97,  lime  24-72,  potash  5 '20,  water  15'90, 
fluorine  2 '10 =100 '89.  It  maybe  taken  as  a  unisilicate  if  part  of  the  silica  is  considered 
accessory. 

Pyr.,  etc. — In  the  closed  tube  exfoliates,  whitens,  and  yields  water,  which  reacts  acid.  In 
the  open  tube,  when  fused  with  salt  of  phosphorus,  gives  a  fluorine  reaction.  B.B.  exfoliates, 
colors  the  flame  violet  (potash),  and  fuses  to  a  white  vesicular  enamel.  F.  =  1'5.  Decom- 
posed by  hydrochloric  acid,  with  separation  of  slimy  silica. 

Diff. — Distinguishing  characters  :  its  occurrence  in  square  prisms  ;  its  perfect  basal  cleav- 
age, and  pearly  lustre  on  the  base. 

Obs. — Occurs  commonly  in  amygdaloid  and  related  rocks,  with  various  zeolites  ;  also  occa- 
sionally in  cavities  in  granite,  gneiss,  etc.  Greenland,  Iceland,  the  Faroe  Islands,  Andreas- 
berg,  Poonah  and  Ahmednuggar  in  Hindostan,  afford  fine  specimens.  In  America,  found  in 
Nova  Scotia  ;  Bergen  Hill,  N.  J.;  the  Cliff  mine,  Lake  Superior  region. 

CIIALCOMOKPIIITE  (v.  Rath},  from  limestone  inclosures  in  the  lava  of  Niedermend  g. 
Hexagonal.  Essentially  an  hydrous  calcium  silicate. 

EDINGTONITE.— Analysis  by  Heddle,  SiOa  36-98,  A103  22-63,  BaO  26 '84,  CaO  tr,  Na2O  tr., 
H.O  12-46=98-91.  Tetragonal.  Dumbarton,  Scotland. 

GISMONDITE.— Analysis,  Marignac,  SiO2  35 "38,  A103  27'23,  CaO13'12,  K2O2-85,  H.2O21'10 
=  100-18.  Capo  di  Bove,  near  Rome  ;  Baumgarten,  near  G-iessen,  etc. 

CARPHOLITE. — In  radiated  tufts  in  the  tin  mines  of  Schlackenwald  ;  Wippra  in  the  Harz. 
Bases  mostly  in  sesquioxide  state  ( 


SUBSILICATES. 


ALLOPHANE. 


Amorphous.  In  incrustations,  usually  thin,  with  a  mammillary  surface, 
and  hyalite-like  ;  sometimes  stalactitic.  Occasionally  almost  pulverulent. 

H.  —  3.  G.  =  1*85-1'89.  Lustre  vitreous  to  subresinous ;  bright  and 
waxy  internally.  Color  pale  sky-blue,  sometimes  greenish  to  deep  green, 
brown,  yellow,  or  colorless.  Streak  uncolored.  Translucent.  Fracture 
imperfectly  conchoidal  and  shining,  to  earthy.  Yery  brittle. 

Comp — Q.  ratio  for  Al  :  Si  :  H,  mostly=3  :  2  :  6  (or  5) ;  AlSiO5+6aq,  or  AlSi05+5aq= 
Silica  23'75,  alumina  40  "62,  water  35 '63  =  100.  Plumbattophane,  from  Sardinia,  contains  a 
little  lead. 

The  coloring  matter  of  the  blue  variety  is  due  to  traces  of  chrysocolla,  the  green  to  mala- 
chite, and  that  of  the  yellowish  and  brown  to  iron. 

Pyr.,  etc — Yields  much  water  in  the  closed  tube.  B.B.  crumbles,  but  is  infusible.  Givea 
a  blue  color  with  cobalt  solution.  Gelatinizes  with  hydrochloric  acid. 

Obs. — Allophane  is  regarded  as  a  result  of  the  decomposition  of  some  aluminous  silicate 
(feldspar,  etc.) ;  and  it  often  occurs  incrusting  fissures  or  cavities  in  mines,  especially  those 
of  copper  and  limonite,  and  even  in  beds  of  coal.  Found  at  Schneeberg  in  Saxony  ;  at  Gers- 
bach  ;  at  the  Chessy  copper  mine,  near  Lyons ;  near  Woolwich,  in  Kent,  England.  In  the 
XT.  S.  it  occurs  at  Richmond,  Mass.;  at  the  Friedensville  zinc  mines,  Pa.,  etc. 

COLLYRITE. — A  hydrous  silicate  of  aluminum.  Clay-like  in  structure,  white.  Hove, 
England ;  Schemnitz. 

URANOPIIANE,  from  Silesia,  and  URANOTILE  ,  from  Wolsendorf,  Bavaria,  are  silicates  con- 
taining uranium. 


320 


DESCRIPTIVE   MINERALOGY. 


II.  ZEOLITE  SECTION. 


THOMSONITE.     Comptonite. 


Orthorhombie. 


7A  7=  90°  40' ;  O  A 14  =  144°  9' ;  c  :  I  :  a  =0-7225  : 
1*0117  :  1.  Cleavage:  i-l  easily  obtained  ;  i-l  less  so; 
O  in  traces.  Twins :  cruciform,  having  the  vertical 
axis  in  common.  Also  columnar,  structure  radiated  ; 
in  radiated  spherical  concretions ;  also  amorphous  and 
compact. 

H.=5-5-5.  G.— 2-3-2-4.  Yitreous,  more  or  less 
pearly.  Snow-white  ;  impure  varieties  brown.  Streak 
uncolored.  Transparent — translucent.  Fracture  uneven. 
Brittle.  Pyroelectric.  Double  refraction  weak  ;  optic- 
axial  plane  parallel  to  O\  bisectrix  positive,  nornml 
to  i-l ;  divergence  82°-82i°  for  red  rays,  from  Dumbarton  ;  DesCl. 

Var — Ordinary,  (a)  In  regular  crystals,  usually  more  or  less  rectangular  in  outline.  •(&) 
In  slender  prisms,  often  vesicular  to  radiated,  (c)  Radiated  fibrous,  (d)  Spherical  concre- 
tions, consisting  of  radiated  fibres  or  slender  crystals,  (e)  Massive,  granular  to  impalpable, 
and  white  to  reddish-brown.  Ozarkite  is  massive  thorn sonite  ;  rauite  (Norway)  is  related. 

Comp.— Q.  ratio  for  R(=Ca,Naa)  :  ft(Al)  :  Si  :  H=]  :  3  :  4  :  2|,  Ca  :  Na2  =  2  :  1,  or  3  :  1  ; 
formula  2(Ca,Na2)MSi2Ob-f5aq.  Analysis,  Rammelsberg,  Dumbarton,  Si02  38'09.  A103 
31-62,  CaO  12-60,  Na2O  4'62,  H20  13-40=100'20. 

Pyr.,  etc. — At  a  red  heat  loses  13 '3  p.  c.  of  water,  and  the  mineral  becomes  fused  to  a 
white  enamel.  B.B.  fuses  with  intumescence  at  2  to  a  white  enamel.  Gelatinizes  with 
hydrochloric  acid. 

Obs. — Found  in  cavities  in  lava  and  other  igneous  rocks  ;  and  also  in  some  metamorphic 
rocks,  with  elseolite.  Occurs  near  Kilpatrick,  Scotland  ;  in  the  lavas  of  Sorrm-ia,  (comptonite) ; 
in  Bohemia ;  in  Sicily  ;  in  Faroe  ;  the  Tyrol,  at  Theiss ;  at  Monzoni,  Fassathal ;  at  Peter's 
Point,  Nova  Scotia  ;  at  Magnet  Cove,  Arkansas  (ozarkite}. 


NATROLITE.    Mesotype.    Nadelzeolith,  Germ. 

Orthorhombic.  7  A  7=  91°,  O  A  I-i  =  144°  23';  c  \l\  d  =  0-35825  : 
1-0176  :  1.  Crystals  usually  slender,  often  acicular  ;  fre- 
quently interlacing  ;  divergent,  or  stellate.  Also  fibrous, 
radiating,  massive,  granular,  or  compact. 

H.=5-5-5.  G.=2-17-2-25 ;  2-249,  Bergen  Hill, 
Brush.  Lustre  vitreous,  sometimes  inclining  to  pearly, 
especially  in  fibrous  varieties.  Color  white,  or  colorless ; 
also  grayish,  yellowish,  reddish  to  red.  Streak  uncolored. 
Transparent — translucent.  Double  refraction  weak  ;  op- 
tic-axial plane  i-l ;  bisectrix  positive,  parallel  to  edge 
7/7;  axial  divergence  94°-96°,  red  rays,  for  Auvergne 
crystals  ;  95°  12'  for  brevicite ;  DesCl. 

Comp.— Q.  ratio  for  R  :  R  :  Si  :  H=l  :  3  :  6  :  2 ;  and  for  R  :  Si= 

2  :  3(R=Na2,3R=R) ;  formula  N0*MS*tQa«+Sif^==8iliqa  47'29,  alumina  20 "9(5,  soda  16'30, 
water  9 -45 =100. 

Pyr.,  etc -In  the  closed  tube  loses  water,  whitens  and  becomes  opaque.  B.B.  fuses  quietly 

at  2  to  a  colorless  glass.     Fusible  in  the  flame  of  an  ordinary  stearine  or  wax  candle.     Gela- 
tinizes with  acids. 


T\ 


OXYGEN   COMPOUNDS — HYDROUS    SILICATES. 


321 


Diff. — Some  varieties  resemble  pectolite,  thomsonite,  but  distinguished  B.B. 

Obs. — Occurs  in  cavities  in  amygdaloidal  trap,  basalt,  and  other  igneous  rocks  ;  and  some- 
times in  seams  in  granite,  gneiss,  and  syenite.  It  is  found  in  Bohemia  ;  in  Auvergne  ;  Fassa- 
thal,  Tyrol ;  Kapnik  ;  at  Glen  Farg  in  Fifeshire ;  in  Dumbartonshire.  In  North  America, 
occurs  in  the  trap  of  Nova  Scotia ;  at  Bergen  Hill,  N.  J.  ;  at  Copper  Falls,  Lake  Superior. 


16*'; 


SCOLECITE.    Poonahlite. 

Monoclinic.     O=  89°  6',  /A  7=  91°  36',  O  A  14  =  161 
—  03485  :  1-0282  :  1.     Crystals  long  or  short  prisms,  or 
acicular,  rarely  well  terminated,  and  always  compound. 
Twins:  twinn  ing-plane  i-i.     Cleavage:  I  nearly  perfect. 
Also  in  nodules  or  massive ;  fibrous  and  radiated. 

II. =5-5 -5.  G.  =  2-16-2-4.  Lustre  vitreous,  or  silky 
when  fibrous.  Transparent  to  subtranslucent.  Pyro- 
electric,  the  free  end  of  the  crystals  the  antilogne  pole. 
Double  refraction  weak  ;  optic-axial  plane  normal  to  i-l ; 
divergence  53°  41/,  for  the  red  rays ;  bisectrix  negative, 
parallel  to  i-l ;  plane  of  the  axis  of  the  red  rays  and  their 
bisectrix  inclined  about  17°  8'  to  i-i,  and  93°  3'  to  \-i. 


Comp.— Q.  ratio  f  or  R  :  R-  :  Si  :  H=l  :  3  :  6  :  3  ;  forR(3R=ft)  :  Si=2  :  3,  as  in  natrolite ; 
R=Ca,:ft=Al;  formula  CaAlSi3010+oaq  =  Silica  45 '85,  alumina  28'13,  lime  14-26,  water 
13 -76= 100. 

Pyr.,  etc. — B.B.  sometimes  curls  up  like  a  worm  (whence  the  name  from  o-Kd>\-n£,  a  worm, 
which  gives  scoltcite,  and  not  scolesite  or  scolezite)  ;  other  varieties  intumesce  but  slightly,  and 
all  fuse  at  2-2 '2  to  a  white  blebby  enamel.  Gelatinizes  with  acids  like  natrolite. 

Diff. —  Characterized  by  its  pyrognostics. 

Obs. — Occurs  in  the  Berufiord,  Iceland  ;  also  at  Staffa  ;  inSkye,  atTalisker  ;  near  Poonah, 
Hindostan  (Poonahlite) ;  in  Greenland  ;  at  Pargas,  Finland,  etc. 

MESOLITE. — (Ca,Na2)MSi3O10+3aq  (5  p.  c.  Na2O).    Near  scolecite.    Iceland  ;  Nova  Scotia. 

LEVYNITE.— Rhombohedral  Q.  ratio  forR  :  R  :  Si  :  H=l  :  3  :  6  :  4.  Analysis,  Damour, 
Iceland,  Si02  45  "76,  A103  23  "56,  CaO  10  57,  Na20  1'36,  K20  1'64,  H20  17 '33=100-22.  Ire- 
land ;  Faroe  ;  Iceland. 


ANALCITE. 

Isometric  (?) .  Usually  in  trapezohedrons  (f.  54,  p.  18).  Cleavage  ; 
cubic,  in  traces.  Also  massive  granular. 

H.  =  5-5-5.  G-.=2-22-2-29 ;  2-278,  Thomson.  Lustre  vitreous.  Color- 
less ;  white  ;  occasionally  grayish,  greenish,  yellowish,  or  reddish-white. 
Streak  white.  Transparent — nearly  opaque.  Fracture  subconchoidal, 
uneven.  Brittle. 


Comp.— Q.  ratio  f  or  R  :  R  :  Si  :  H=l  :  8  :  8  :  2,  R=Na2,  R=A1=3R ;  R  :  Si=l  :  2.  For- 
mula Na2AlSi4O12  +  2aq=:Silica  54 '47,  alumina  23'29,  soda  14'07,  water  817=100. 

Pyr.,  etc. — Yields  water  in  the  closed  tube.  B.B.  fuses  at  2*5  to  a  colorless  glass.  Gelati- 
nizes with  hydrochloric  acid. 

Diff. — Distinguishing  characters  :  crystalline  form  ;  absence  of  cleavage  ;  fusion  B.B.  with- 
out intumescence  to  a  clear  glass  (unlike  chabazite). 

Obs. — Some  localities  are  :  the  Tyrol ;  the  Kilpatrick  Hills  in  Scotland ;  the  Faroe  Islands  ; 
Iceland ;  Aussig,  Bohemia ;  Nova  Scotia  ;  Bergen  Hill,  New  Jersey  ;  the  Lake  Superior 
region. 

Schrauf  has  found  that  the  analcite  of  Friedeck,  Bohemia,  is  properly  tetragonal;  the 
simplest  crystals  showing  evidence  of  repeated  twinning. 
21 


322 


DESCRIPTIVE   MINERALOGY. 


FAUJASITE. — An  octahedral  zeolite  from  the  Kaiserstuhlgebirge.  Analysis,  Damour,  SiO2 
46-12,  A103  16-81,  CaO  4'79,  Na20  5 '09,  H2O  27 '02=99-83. 

EUDNOPHITE.     Near  analcite.     In  syenite  near  Brevig,  Norway. 

PILINITE.  —In  slender  needles  (orthorhombic) ;  white  ;  lustre  silky.  Analysis  Si02  55-70, 
AlO3(FeO3)  18-64,  CaO  19.51,  L120  (1-18),  H20  4 -97=100.  In  granite  of  Striegau,  Silesia 
(Lasaulx). 


CHABAZITE. 


Khornbohedral.  E  A  R  =  94°  46',  0  A  R  =  129°  15'  ;  c  =  1'06.  Twins  : 
twinning-plane  0,  very  common,  and  usually  in  compound  twins,  as  in 
f  .  644  ;  also  7?,  rare.  Cleavage  rhombohedral,  rather  distinct. 


643 


Haydenite. 


G.= 2-08-2-19.  Lustre  vitreous.  Color  white,  flesh-red  ; 
streak  uncolored.  Transparent — translucent.  Fracture  uneven.  Brittle. 
Double  refraction  weak ;  in  polarized  light,  images  rather  confused ;  axis 
in  some  crystals  (Bohemia)  negative,  in  others  (from  Andreasberg)  posi- 
tive ;  DesCl. 


Var. — 1.  Ordinary.  The  most  common  form  is  the  fundamental  rhombohedron,  in  which 
the  angle  is  so  near  90°  that  the  crystals  were  at  first  mistaken  for  cubes.  Acadialile,  from 
Nova  Scotia  (Acadia  of  the  French  of  last  century),  is  only  a  reddish  chabazite  ;  sometimes 
nearly  colorle?s.  In  some  specimens  the  coloring  matter  is  arranged  in  a  tesselated  manner, 
or  in  layers,  with  the  angles  almost  colorless.  2.  Phacolite  is  a  colorless  variety  occurring  in 
twins  of  mostly  a  hexagonal  form,  and  often  much  modified  so  as  to  be  lenticular  in  shape 
(whence  the  name,  from  <t>a/cos,  a  bean}  ;  the  original  was  from  Leipa  in  Bohemia;  R/\R 
=94°  24',  fr.  Oberstein,  Breith. 

Comp.— Making  part  of  the  water  basic  (at  300°  C.  loses  17-19  p.  c.)  Rammelsberg  writes 
the  formula  (H,K)2CaAlSi5015  +  aq,  where  the  Q.  ratio  for  R  :  ft  :  Si-2  :  3  :  10,  R  =  H,,Na2, 
Ca;  or  (3R— R),  R  :  Si=l  :  2.  The  formula  corresponds  to  Silica  50'50,  alumina  17'26,  lime 
9-43,  potash  1'98,  water  20'83  =  100. 

Pyr.j  etc. —  B.B.  intumesces  and  fuses  to  a  blebby  glass,  nearly  opaque.  Decomposed  by 
hydrochloric  acid,  with  separation  of  slimy  silica. 

Diff. — Its  rhombohedral  form,  resembling  a  cube,  is  characteristic  ;  is  harder,  and  does  not 
effervesce  with  acids  like  calcite  ;  is  unlike  fluorite  in  cleavage  ;  fuses  B.  B.  with  intumes- 
cence to  a  blebby  glass,  unlike  analcite. 

Obs. — Chabazite  occurs  mostly  in  trap,  basalt,  or  amygdaloid,  and  occasionally  in  gneiss, 
syenite,  mica  schist,  hornblendic  schist.  At  the  Faroe  Islands,  Greenland,  and  Iceland  ;  at 
Aussig  in  Bohemia  ;  Striegau,  Silesia.  In  Nova  Scotia,  wine-yellow  or  flesh-red  (the  last  the 
acadi/dlte},  etc.;  at  Bergen  Hill,  N.  J. ;  at  Jones's  Falls,  near  Baltimore  (haydenite). 

SEEBACHITE  (Bauer]  from  Richmond,  Victoria,  is,  according  to  v.  Rath,  identical  with 
phacolite  ;  and  he  suggests  the  same  may  be  true  of  HERSCHELITE,  from  Aci  Castello,  Sicily. 


OXYGEN    CO^IPOUNDS — HYDROUS    SILICATES. 


323 


GMELINITE. 


645 


Khombohedral.  E  A  R  =  112°  26',  O/\R=  O  A-l  =  140°  3' ;  c  = 
0-7254.  Crystals  usually 
hexagonal  in  aspect ;  some- 
times habit  rhombohedral ; 
i  often  horizontally  stri- 
ated. Cleavage:  a  perfect. 
Observed  only  in  crystals, 
and  never  as  twins. 

IL=4-5.  G-.  =  2-04-2-17. 
Lustre  vitreous.  Colorless, 
yellowish-white,  greenish- 
white,  reddish-white  flesh- 
red.  Transparent  to  trans-  C.  Blomidon,  etc. 
lucent.  Brittle. 


C.  Blomidon. 


Comp.— Q.  ratio  f  or  R  :  R  :  Si  :  H=l  :  3  :  8  :  6,  R=Ca(Na2,Ka),  R=A1.  Formula  (Ca,Na2) 
A-lSuOio+6aq.  Analysis  by  Howe,  Bergen  Hill,  SiO,  48 -67,  A1O3  18-72,  FeO3  O'lO,  CaO 
2-60,  Na2O  9-14,  H2O  21 '35 =100 '58  (Am.  J.  Set,  III.,  xii.,  270,  1876). 

Pyr.j  etc. — In  the  closed  tube  crumbles,  gives  off  much  water.  B.  B.  fuses  easily  to  a  white 
enamel.  Decomposed  by  hydrochloric  acid  with  gelatinization.  . 

Diff. — Closely  resembles  some  chabazite,  but  differs  decidedly  in  angle. 

Obs. — Occurs  at  Andreasberg;  in  Translyvania  ;  in  Antrim,  Ireland  ;  near  Larne ;  at  Talisker 
in  Skye ;  at  Cape  Blomidon  and  other  localities  in  Nova  Scotia  (ledererite) ;  in  fine  crystals  of 
varied  habit  at  the  Bergen  HiU  tunnel  of  1876. 

PHILLIPSITE. 

Orthorhombic.  IM=  91°  12' ;  1  A  1  =  121°  20',  120°  44',  and  88°  40', 
Marisrnac.  Faces  1  and  i-l  striated  parallel  to 


the  edge  between  them.  Simple  crystals  un- 
known. Commonly  in  cruciform  crystals,  consist- 
ing of  two  crossing  crystals,  each  a  twinned 
prism  (f.  647).  Crystals  either  isolated,  or 
grouped  in  tufts  or  spheres  that  are  radiated 
within  and  bristled  with  angles  at  surface. 

H.  =4-4-5.  G.  =2-201.  Lustre  vitreous. 
Color  white,  sometimes  reddish.  Streak  un- 
colored.  Translucent — opaque. 

Comp Q.  ratio  for  R  :  ft  :  Si  :  H=l  :  3  :  8  :  4,  E=Ca 

and  Ka(Naa) ;  Ca  :  K2=3  :  1,  2  :  3,  etc.  Formula  RcVlSi4O12 
+4aq.  Analysis  by  Ettling,  Nidda.  Hessen,  SiO2  4813, 
A103  21-41,  CaO  8-21,  K*O  5 "20,  Na2O  0'70,  H20  1078= 
100-48. 

Pyr.,  etc.— B.B.  crumbles  and  fuses  at  3  to  a  white  enamel. 
Gelatinizes  with  hydrochloric  acid. 

Diff. — Resembles  harmotome,  but  distinguished  B.B. 

Obs, — At  the  Giant's  Causeway,  Ireland ;  at  Capo  di  Bove, 
near  Rome  ;  in  Sicily  ;  Annerode,  near  Giessen ;  in  Silesia ; 
Bohemia  ;  on  the  west  coast  of  Iceland. 

Strong  (Jahrb.  Min.,  1876,  585)  shows  that  the  forms  are 
exactly  analogous  to  those  of  harmotome,  and  suggests  that 
it  may  be  also  monoclinic. 


647 


C.  di  Bove. 


DESCRIPTIVE   MINERALOGY. 


HARMOTOME. 


Monoclinic  (DesCloizeaux).     Cleavage 


/,  0,  easy.  Simple  crystals  un- 
known. Occurring  in  penetra- 
tion-twins. Unknown  massive. 
H.  =4-5.  G.  =2-44-2-45. 
Lustre  vitreous.  Ct)lor  white  ; 
passing  into  gray,  yellow,  red, 
or  brown.  Streak  white.  Sub- 
transparent — translucent.  Frac- 
ture uneven,  imperfectly  con- 
choidal.  Brittle. 


Comp.— Q.  ratio  for  R  :  R  :  Si  :  H 
=  1:3:10:5;    here    R=Ba   mostly, 

Andreasberg.  algo  Ka  .   R=A1      Formula  RAlSi5014 

+5aq.      If   one -fifth   of   the   water   is 

chemically  combined   (Rammelsberg),  then  the  formula  corresponds  to  H2RAlSi5O]5+4aq. 
Both  formulas  give  Silica  45-91,  alumina  1570,  baryta  20-06,  potash  3 '34,  water  14-99=100. 
Pyr.,  etc. — B.B.  whitens,  then  crumbles  and  fuses  at  3'5  without  intumescence  to  a  white 
translucent  glass.     Some  varieties  phosphoresce  when  heated.     Decomposed  by  hydrochloric 
acid  without  gelatinizing. 

Diff. — Characterized  by  its  crystallization  in  twins ;  the  presence  of  barium  separates  it 
from  other  species. 

Obs. — Harmotome  occurs  in  amygdaloid,  phonolyte,  trachyte;  also  on  gneiss,  and  in  some 
metalliferous  veins.  At  Strontian  in  Scotland ;  at  Andreasberg ;  at  Rudelstadt  in  Silesia ; 
Schiffenberg,  near  G-iessen,  etc. ;  Oberstein  ;  in  the  gneiss  of  upper  New  York  City. 

DesCloizeaux,  who  has  shown  the  monoclinic  character  of  the  species  by  optical  means,  has 
adopted  a  different  position  for  the  crystals  (1=7,  etc.). 


Strontian. 


STILBITE.    Desmine. 


Orthorhombic.  /A  1  =  94°  16',  1  A 1,  front,  =  119°  16',  side,  114°  0'. 
Cleavage  :  i-l  perfect,  i-l  less  so.  Forms  as  in  f.  650 ; 
more  common  with  the  prism  flattened  parallel  to  i-$ 
or  the  cleavage-face,  and  pointed  at  the  extremities. 
Twins :  cruciform,  twinning-plane.  1-^,  rare.  Common 
in  sheaf -like  aggregations ;  divergent  or  radiated  ;  some 
times  globular  and  thin  lamellar-columnar. 

H.  =  3-5-4.  G.= 2-094-2-205.  Lustre  of  i4  pearly  ; 
of  other  faces  vitreous.  Color  white ;  occasionally 
yellow,  brown,  or  red,  to  brick-red.  Streak  uncolored. 
Transparent — translucent.  Fracture  uneven.  Brittle. 

Var. — 1.    Ordinary.     Either  (a)  in  crystals,  flattened  and  pearly 
parallel  to  the  plane  of  cleavage,  or  sheaf -like,  or  divergent  groups  ; 
or  (b)  in  radiated  stars  or  hemispheres,  with  the  radiating  individuals 
showing  a  pearly  cleavage  surface.    Sphcerostiibite,  Beud ,  is  in  spheres, 
radiated  within  with  a  pearly  fracture,  rather  soft  externally. 
Comp.— Q.  ratio  for  R  :  ft  :  Si  :  H=l  :  3  :  12  :  6  ;  R=Ca(Na2),R=:Al.  Formula  RAlSieOi6 
+ 6aq.     If  two  parts  of  water  are  basic  (Ramm.)  the  ratio  becomes  (R=Ca,H2,Na2)  3  :  3  :  12 
:  4,  or  R  :  Si=l  :  2,  and  the  formula  is  H4RAlSi6Oi8+4aq.     Analysis,  Petersen,  Seisser  Alp, 
Si02  55-61,  A103  15-62,  CaO7'33,  Na2O  2'01,  K2O  0'47,  H2O  18'19=99-23. 
Pyr.,  etc. — B.B.  exfoliates,  swells  up,  curves  into  fan-like  or  vermicular  forms,  and  fuses 


OXYGEN   COMPOUNDS IIYDKOUS    SILICATES.  325 

to  a  white  enamel.  F.— 2-2'5.  Decomposed  by  hydrochloric  acid,  without  gelatinizing.  The 
sphcerostilbite  gelatinizes,  but  Heddle  says  this  is  owing  to  a  mixture  of  mesolite  with  the  stil- 
bite. 

Diff. — Prominent  characters:  occurrence  in  sheath-like  forms,  and  in  the  rectangular 
tabular  crystals ;  lustre  on  cleavage-face  pearly  ;  does  not  gelatinize  with  acids. 

Obs. — Stilbite  occurs  mostly  in  cavities  in  amygdaloid.  It  is  also  found  in  some  metal- 
liferous veins,  and  in  granite  and  gneiss.  The  Faroe  Islands,  Iceland,  and  the  Isle  of  Skye  ; 
in  Dumbartonshire,  Scotland ;  at  Andreasberg  ;  Arendal  in  Norway ;  in  the  Vendayah  Mts. , 
Hindostan ;  near  Fahlun  in  Sweden.  In  North  America,  at  Bergen  Hill,  New  Jersey  ;  at  the 
Michipicoten  Islands,  Lake  Superior ;  Nova  Scotia,  etc. 

The  name  stilbite  is  from  arU/fy,  lustre ;  and  desmine  from  Mapi?,  a  bundle.  The  species 
stilbite,  as  adopted  by  Haiiy,  included  Strahlzeolith  Wern.  (radiated  zeolite,  or  the  above), 
and  Blatterzeolith  Wern.  (foliated  zeolite,  oi4  the  species  heulaudite  beyond;.  The  former  was 
the  typical  part  of  the  species,  and  is  the  firs£  mentioned  in  the  description  ;  and  the  latter 
he  added  to  the  species,  as  he  observes,  with  much  hesitation.  In  1817,  Breithaupt  separated 
the  two  zeolites,  and  called  the  former  desmine  and  the  latter  euzeolite,  thus  throwing  aside 
entirely,  contrary  to  rule  and  propriety,  Haiiy's  name  stilbite,  which  should  have  been  accepted 
by  him  in  place  of  desmine,  it  being  the  typical  part  of  his  species.  In  1822,  Brooke  (ap- 
parently unaware  of  what  Breithaupt  had  done)  used  stilbite  for  the  first,  and  named  the  other 
heulandite  In  this  he  has  been  followed  by  the  French  and  English  mineralogists,  while  the 
Germans  have  unfortunately  followed  Breithaupt. 

EPISTILBITE  (Reissite). — Composition  like  heulandite,  but  form  orthorhombic.  Iceland; 
Faroe ;  Poonah,  India,  etc.  ;  Bergen  Hill,  N.  J. 

FORESITE.— Resembles  stilbite  in  form.  Q.  ratio  for  R  :  R  :  Si  :  H— 1  :  6  :  12  :  6.  Formula 
RAl2Si6O19+()aq.  (R=Na2  :  Ca=l  :  3).  Occurs  in  crystalline  crusts  on  tourmaline,  in  cavities 
in  granite.  Island  of  Elba. 


HEULANDITE.     Stilbit,  Germ. 

Monoclinic.   C  =  88°  35',  I/\  1=  136°  4',  O  A 14  =  156°  45' ;  c  :  I  :  d  = 
1-065  :  2-4785  :  1.      Cleavage  :    clinodiagonal  (i-l)  emi- 
nent.    Also  in  globular  forms ;  also  granular.  651 

H.=3'5-4.  G.=2-2.  Lustre  of  i-i  strong  pearly  ;  of 
other  faces  vitreous.  Color  various  shades  of  white, 
passing  into  red,  gray,  and  brown.  Streak  white. 
Transparent — subtranslucent.  Fracture  subconchoidal, 
uneven.  Brittle.  Double  refraction  weak  ;  optic-axial 
plane  normal  to  i-i ;  bisectrix  positive,  parallel  to  the 
horizontal  diagonal  of  the  base  ;  DesCl. 

Comp.— Q.  ratio  for  R  :  R  :  Si  :  H=l  :  3  :  12  :  5 ;  R=Ca(Na2). 
Formula  CaAlSi6Oi 6 +5aq,  or  if  2H,O  be  basic  (Ramm.)  then  the 
ratio  becomes  1:1:4  (R=Ca  and  H2),  and  the  formula  H4CaAlSi6 
Oi8+3aq.  Both  require  Silica  59-06.  alumina  16 '83,  lime  7 '88,  soda 
1-46,  water  14-77=100. 

Pyr.— B.B.  same  as  with  stilbite. 

Diff,. — Distinguished  by  its  crystalline  form.     Pearly  lustre  of  i-l  a  prominent  character. 

Obs. — Heulandite  occurs  principally  in  amygdaloidal  rocks.  Also  in  gneiss,  and  occasionally 
in  metalliferous  veins.  Occurs  in  Iceland ;  the  Faroe  Islands ;  the  Vendayah  Mountains, 
Hindostan.  Also  in  the  Kilpatrick  Hills,  near  Glasgow ;  in  the  Fassa  Valley,  Tyrol ;  An- 
dreasberg;  Nova  Scotia,  etc. ;  at  Bergen  Hill,  New  Jersey  ;  on  north  shore  of  Lake  Superior ; 
at  Jones's  Falls,  near  Baltimore  (Levy's  beaumontite). 

For  the  relation  of  the  synonymes  see  stilbit,  above. 

BREWSTERITE. — Q.  ratio  same  as  for  heulandite,  but  R  is  here  Ba  or  Sr  (Ca).  Formula 
requires  Si02  53-5,  A103  15 '3,  BaO  7-6,  SrO  10 '2,  H20  13 '4= 100.  Monoclinic.  Strontian  in 
Argyleshire,  etc. 


326  DESCRIPTIVE   MINERALOGY". 

III.    MARGAROPHYLLITE    SECTION. 
BISILICATES. 

The  Margarophyllites  are  often  foliated  like  the  micas,  and  the  name 
alludes  to  the  pearly  folia.  Massive  varieties  are,,  however,  the  most  com- 
mon with  a  large  part  of  the  species,  and  they  often  have  the  compactness 
of  clay  or  wax.  Talc,  pyrophyllite,  serpentine,  are  examples  of  species  pre- 
senting both  extremes  of  structure  ;  while  pinite  occurs,  as  thus  far  known, 
only  in  the  compact  condition.  The  true  Margarophyllites  are  below  5  in 
hardness ;  greasy  to  the  feel,  at  least  when  finely  powdered. 

TALC. 

Orthorhombic.     /A  7=120°.     Occurs  rarely  in  hexagonal  prisms  and 

Elates.     Cleavage:  basal,  eminent.     Foliated  massive,  sometimes  in  globu- 
ir  and  stellated  groups  ;  also  granular  massive,  coarse  or  fine ;  also  com  - 
pact  or  cryptocrvstalline. 

H.=1-1'5.  G.==2*565-2'8.  Lustre  pearly.  Color  apple-green  to  white, 
or  silvery-white ;  also  greenish-gray  and  dark  green  ;  sometimes  bright 
green  perpendicular  to  cleavage  surface,  and  brown  and  less  translucent  at 
right  angles  to  this  direction  ;  brownish  to  blackish-green  and  reddish  when 
impure.  Streak  usually  white ;  of  dark  green  varieties,  lighter  than  the 
color.  Subtransparent — subtranslucent.  Sectile.  Thin  laminae  flexible, 
but  not  elastic.  Feel  greasy.  Optic-axial  plane  i-l ;  bisectrix  negative,  nor- 
mal to  the  base ;  DesCl. 

Var. — Foliated,  Talc.  Consists  of  folia,  usually  easily  separated,  having  a  greasy  feel,  and 
presenting  ordinarily  light  green,  greenish-white,  and  white  colors.  G.  =  2  '55-2 '78 .  (a) 
Massive,  Steatite  or  Soapstone  (Speckstein,  Germ.}.  Coarse  granular,  gray,  grayish-green,  and 
brownish-gray  in  colors.  H.  =1-2 '5.  (b)  Fine  granular  or  cryptocrystalline.  and  soft  enough 
to  be  used  as  chalk,  as  the  French  chalk  (Craie  de  Brianqon],  which  is  milk-white,  with  a 
pearly  lustre. 

Comp. — Q.  ratio  for  Mg  :  Si=2  :  5,  or  3  :  4,  with  a  varying  amount  of  water  in  both  talc  and 
steatite,  from  a  fraction  of  a  per  cent,  to  7  p.  c.  If  the  water  is  basic,  the  ratio  becomes  f  or 
R  :  Si=l  :  2,  (R=Mg(Fe)  and  H3),  and  the  formula  is  H2Mg3Si4Oi2  (Ramm.)  — Silica  03-49, 
magnesia  31'75,  water  4'76  =  100  ;  the  analyses  show  generally  1  or  2  p.  c.  of  FeO. 

Pyr.,  etc. — In  the  closed  tube  B.B.,  when  intensely  ignited,  most  varieties  yield  water.  In 
the  platinum  forceps  whitens,  exfoliates,  and  fuses  with  difficulty  on  the  thin  edges  to  a  white 
enamel.  Moistened  with  cobalt  solution,  assumes  on  ignition  a  pale  red  color.  Not  decom- 
posed by  acids. 

Diff. — Recognized  by  its  extreme  softness,  unctuous  feel,  and  usually  foliated  structure. 
Inelastic  though  flexible.  Yields  water  onJy  on  intense  ignition. 

/     Obs. — Talc  or  steatite  is  a  very  common  mineral,  and  in  the  latter  form  constitutes  exten-^ 
sive  beds  in  some  regions.     It  is  often  associated  with  serpentine  and  dolomite,  and  frequently 
contains  crystals  of  dolomite,  breunerite,  asbestus,  actinolite,  tourmaline,  magnetite.     Steatite 
is  the  material  of  many  pseud  omorphs,  among  which  the  most  common  are  those  after  pyroxene, 
hornblende,  mica,  scapolite,  and  spinel.       The  magnesian  minerals  are  those  which  commonly 
afford  steatite  by  alteration ;  while  those,  like  scapolite  and  nephelite,  which  contain  soda  and 
no  magnesia,  most  frequently   change   to    pinite-like    pseudomorphs.      lienssdaerite   and  , 
pyrattolite  are  pseudomorphous  varieties. 

Apple-green  talc  occurs  near  Salzburg ;  in  the  Valais ;  also  in  Cornwall,  near  Lizard  Point, 
with  serpentine ;  in  Scotland,  with  serpentine,  at  Portsoy  and  elsewhere ;  etc.  In  N. 
America,  some  localities  are :  Vermont,  at  Bridgewater ;  Grai'ton,  etc.  In  New  Hampshire, 
at  Pelham,  etc.  In  R  Inland,  at  Smithfield.  In  N.  York,  near  Amity.  InPenn.,  at  Texas; 
at  Chestnut  Hill,  on  the  Schuylkill.  In  Maryland,  at  Cooptown. 


OXYGEN   COMPOUNDS HYDKOUS    SILICATES.  327 


PYROPHYLLITE.    Agalmatolite  or  Pagodite  pt. 

Orthorhombic.  Not  observed  in  distinct  crystals.  Cleavage:  basal 
eminent.  Foliated,  radiated  lamellar;  also  granular,  to  compact  or  crypto- 
crystalline  ;  the  latter  sometimes  slatv. 

H.  =  l-2.  G.= 2-75-2-92.  Lustreof  folia  pearly,  like  that  of  talc;  of 
massive  kinds  dull  or  glistening.  Color  white,  apple-green,  grayish  and 
brownish-green,  yellowish  to  ochre-yellow,  grayish- white.  Subtransparent 
to  opaque.  Laminae  flexible,  not  elastic.  Feel  greasy.  Optic-axial  angle 
large  (about  108°) ;  bisectrix  negative,  normal  to  the  cleavage-plane. 

Var. — (1)  Foliated,  and  often  radiated,  closely  resembling-  talc  in  color,  feel,  lustre,  and 
structure.  (2)  Compact,  massive,  white,  grayish,  and  greenish,  somewhat  resembling  com- 
pact steatite,  or  French  chalk.  This  compact  variety,  as  Brush  has  shown,  includes  part  of 
what  has  gone  under  the  name  of  agalmatolite,  from  China  ;  it  is  used  for  slate-pencils,  and 
is  sometimes  called  pencil-stone. 

Comp. — Q.  ratio  for  Al  :  Si— 1  :  2,  also  in  other  cases  3  :  8,  Formula  for  the  first  case= 
AlSi3Oj+aq  (Ramm.).  Analysis,  Chesterfield,  S.  C.,  by  G-enth,  SiO2  64 '82,  MO3  28'48,  Fe03 
0-90,  MgO  0-33,  CaO  0'55,  H2O  5 -25  =  100-39. 

Pyr.,  etc. — Yields  water.  B.B.  whitens,  and  fuses  with  difficulty  on  the  edges.  The 
radiated  varieties  exfoliate  in  fan-like  forms,  swelling  up  to  many  times  the  original  volume 
of  the  assay.  Heated  with  cobalt  solution  gives  a  deep  blue  color  (alumina).  Partially  decom- 
posed by  sulphuric  acid,  and  completely  on  fusion  with  alkaline  carbonates. 

Obs. — Compact  pyrophyllite  is  the  material  or  base  of  some  schistose  rocks.  The  foliated 
variety  is  often  the  gangue  of  cyanite.  Occurs  in  the  Urals ;  at  Westana,  Sweden ;  near  Ottrez 
in  Luxembourg  ;  in  Chesterfield  Dist.,  S.  C. ;  in  Lincoln  Co.,  Ga. ;  in  Arkansas.  The  compact 
pyrophyllite  of  Deep  River,  N.  C.,  is  extensively  used  for  making  slate  pencils. 

PIIILITE  (cymitoliU),  near  pyrophyllite. 


SEPIOLITE.    Meerschaum,  Germ.     L'Ecurne  de  Mer,  Fr. 

Compact,  with  a  smooth  feel,  and  fine  earthy  texture,  or  clay-like. 

H.  =  2-2'5.  Impressible  by  the  naik  In  dry  masses  floats  on  water. 
Color  grayish-white,  white,  or  with  a  faint  yellowish  or  reddish  tinge. 
Opaque. 


Comp.  —  Q.  ratio  for  R  :  Si  :  TL=l  :  3  :  1,  corresponding  to  Mg-2Si3O8  +  2aq  ;  or,  if  half  the 
water  is  basic,  1:2:  i=H.2Mg_,Si3O9  +  aq=Silica  60-8,  magnesia  271,  water  12-1  =  100.  The 
amount  of  water  present  is  somewhat  uncertain. 

Pyr.,  etc.  —  In  the  closed  tube  yields  first  hygroscopic  moisture,  and  at  a  higher  temperature 
gives  much  water  and  a  burnt  smell.  B.  B.  some  varieties  blacken,  then  burn  white,  and  fuse 
with  difficulty  on  the  thin  edges.  With  cobalt  solution  a  pink  color  on  ignition.  Decomposed 
by  hydrochloric  acid  with  gelatinization. 

Ol»s.  —  Occurs  in  Asia  Minor,  in  masses  in  stratified  earthy  or  alluvial  deposits  at  the  plains 
of  Fjskihi-sher  ;  also  found  in  Greece  ;  at  Hrubschitz  in  Moravia  ;  in  Morocco  ;  at  Vallecas  in 
Spa.n,  in  extensive  beds. 

The  word  meerschaum  is  German  for  sca-fwth,  and  alludes  to  its  lightness  and  color.  Sepio- 
lite,  Glocker,  is  from  cqTria,  cuttle-fish,  the  bone  of  which  is  light  and  porous,  and  also  a  pro- 
diction  of  the  sea. 

APHRODITE.  —  4MgSiO3+3aq.     Resembles  sepiolite.     Longban,  Sweden. 

SMECTITE.  —  Fuller's  earth  pt.     A  greenish  clay  from  Styria. 

MONTMOHILLONITE.  —  A  rose-red  clay  containing  more  alumina  than  smectite,  from  Mont- 
norillon,  France. 

CELADONITE.  —  A  variety  of  "green  earth"  from  Mt.  Baldo,  near  Verona. 

GLAUCONITE.  —  Green  earth  pt.  A  Irpdrous  silicate  of  iron  and  potassium,  but  always 
impure.  Constitutes  the  green  sand  of  the  chalk  and  other  formations  (e.g.,  in  New  Jersey). 

STILPNOMELANE.  —  In  foliated  plates,  or  as  a  velvety  coating.     Essentially  a  hydrous  iron 


328  DESCRIPTIVE    MINERALOGY. 

(Fe)  silicate.  Color  black  to  yellowish-bronze.  Silesia;  Weilburg;  Nassau;  Sterling-  iron 
mine;  Antwerp,  N.  Y.  (chalcodite). 

CHLOROPAL. — Compact,  earthy.  Color  greenish-yellow.  A  hydrated  iron  silicate.  Formula 
FeSi3O9+5aq.  Andreasberg ;  Steinberg  near  Gottingen ;  Nontron  (nontronite),  France,  etc. 

AERINITE. — Perhaps  related  to  chloropal  (Lasaulx).     Color  blue.     Spain. 


UNISILICATES. 
Serpentine  Group. 

SERPENTINE. 

Orthorhombic  (?).  In  distinct  crystals,  but  only  as  pseudomorphs.  Some- 
times foliated,  folia  rarely  separable ;  also  delicately  fibrous,  the  fibres  often 
easily  separable,  and  either  flexible  or  brittle.  Usually  massive,  fine  granu- 
lar to  impalpable  or  cryptocrystalline  ;  also  slaty. 

H.^2-5-4,  rarely  5-5.  G.=2'5-2'65 ;  some  fibrous  varieties  2-2-2-3; 
retirialite,  2'36-2'55.  Lustre  subresirious  to  greasy,  pearly,  earthy  ;  resin- 
like,  or  wax-like ;  usually  feeble.  Color  leek-green,  blackish-green,  oil 
and  siskin-green,  brownish-red,  brownish-yellow ;  none  bright ;  sometimes 
nearly  white.  On  exposure,  often  becoming  yellowish-gray.  Streak  white, 
slightly  shining.  Translucent — opaque.  Feel  smooth,  sometimes  greasy. 
Fracture  conchoidal  or  splintery. 

Var. — Many  unsustained  species  have  been  made  out  of  serpentine,  differing  in  structure 
(massive,  slaty,  foliated,  fibrous),  or,  as  supposed,  in  chemical  composition. 

MASSIVE.  (1)  Ordinary  massive,  (a)  Precious  or  Noble  Serpentine  (Edler  Serpentin,  Germ. ) 
is  of  a  rich  oil -green  color,  of  pale  or  dark  shades,  and  translucent  even  when  in  thick  pieces ; 
and  (b)  Common  Serpentine,  when  of  dark  shades  of  color,  and  subtranslucent.  The  former 
has  a  hardness  of  2 '5-3;  the  latter  of  ten  of  4  or  beyond,  owing  to  impurities.  Bowenite 
(Smithfield,  R.  I.),  is  a  jade-like  variety  with  the  hardness  5'5. 

FOLIATED.  Marmolite  is  thin  foliated ;  the  laminae  brittle  but  easily  separable,  yet  gradu- 
ating into  a  variety  in  which  they  are  not  separable.  G-.  =2*41 ;  lustre  pearly ;  colois  green- 
ish-white, bluish-white,  or  pale  asparagus-green.  From  Hoboken,  N.  J. 

FIBROUS.  Chrysotile  is  delicately  fibrous,  the  fibres  usually  flexible  and  easily  separating  ; 
lustre  silky,  or  silky  metallic ;  color  greenish-white,  green,  olive-green,  yellow,  and  brownish  ; 
Gr.  =2 '219.  Often  constitutes  seams  in  serpentine.  It  includes  most  of  the  silky  amkmthus 
of  serpentine  rocks.  The  original  chrysotile  was  from  Reichenstein. 

Any  serpentine  rock  cut  into  slabs  and  polished  is  called  serpentine  marble. 

Comp. — Q.  ratio  for  Mg  :  Si  :  H=3  :  4  :  2,  corresponding  to  Mg3Si2O7+2aq= Silica  43-48, 
magnesia  43 '48,  water  13*04.  But  as  chrysolite  is  especially  liable  to  the  change  to  serpen- 
tine, and  chrysolite  is  a  unisilicate,  and  the  change  consists  in  a  loss  of  some  Mg.  anl  the 
addition  of  water,  it  is  probable  that  part  of  the  water  takes  the  place  of  the  lost  Mg,  so  that 
the  mineral  is  essentially  a  hydrated  chrysolite  of  the  formula  H2Mg3Si2O8  +  aq.  The  lela- 
tion  in  ratio  to  kaolinite  and  pinite  corresponds  with  this  view  of  the  formula. 

Pyr.j  etc. — In  the  closed  tube  yields  water.  B.B.  fuses  on  the  edges  with  difficulty.  F.=: 
6.  Gives  usually  an  iron  reaction.  Decomposed  by  hydrochloric  and  sulphuric  acids.  Chry- 
sotile leaves  the  silica  in  fine  fibres. 

Diff. — Distinguishing  characters :  compact  structure  ;  softness,  being  easily  cut  with  n. 
knife  ;  low  specific  gravity  ;  and  resinous  lustre. 

Obs. — Serpentine  often  constitutes  mountain  masses.  It  frequently  occurs  mixed  witt 
more  or  less  of  dolomite,  magnesite,  or  calcite,  making  a  rock  of  clouded  green,  sometimes 
veined  with  white  or  pale  green,  called  verd  antique,  or  ophiolite.  It  results  from  the  altera- 
tion of  other  rocks,  frequently  chrysolite  rocks.  Crystals  of  serpentine  (pseudomorphous) 
occur  in  the  Fassa  valley,  Tyrol ;  near  Miask  ;  Katharinenberg,  and  elsewhere ;  in  Norway, 


OXYGEN   COMPOUNDS — HYDROUS    SILICATES.  329 

at  Snarum,  etc.  Precious  serpentines  come  from  Sweden ;  the  Isle  of  Man ;  Corsica ; 
Siberia  ;  Saxony,  etc.  In  N.  America,  in  Vermont,  at  New  Fane  ;  Roxbury,  etc.  In  Mass. , 
at  Newburyport  and  elsewhere.  In  Conn.,  near  New  Haven  and  Milford,  at  the  verd-antique 
quarries.  In  N.  York,  at  Brewster,  Putnam  Co.  ;  at  Antwerp,  Jefferson  Co.  ;  in  Gouver- 
neur,  St.  Lawrence  Co.  ;  in  Orange  Co.  ;  Richmond  Co.  In  N.  Jersey,  at  Hoboken.  In 
Pe/ui.,  at  Texas,  Lancaster  Co. ;  also  in  Chester  Co.  ;  in  Delaware  Co.  In  Maryland,  at 
Bare  Hills  ;  at  Cooptown,  Harford  Co. 

The  following  are  varieties  of  serpentine  :  retinalite,  Grenville,  C.  W. ;  vorhauserite.  Tyrol ; 
porcellophite ;  bowenite,  Smithfield,  R.  I.  ;  antigorite,  Piedmont ;  wittiamsite,  Texas,  Pa.  ; 
marmolitc,  Hoboken ;  picrolite  ;  metaxite ;  refdanskite  (containing  Ni) ;  aquacrepitite. 

BASTITE  or  SCHILLER  SPAB. — An  impure  serpentine,  a  result  of  the  alteration  of  a  foliated 
pyroxene.  Baste  ;  Todtmoos  in  the  Schwarzwald.  ANTILLITE  is  similar. 

DEWEYLITE  (Gymnite). — H,Mg>4Si309+4aq.  Occurs  with  serpentine  at  Middlefield  ami 
Texas,  Penn.  HYDROPHITE  (Jenkinsite],  near  deweylite,  but  Mg  replaced  in  part  by  Fe. 

GEROLITB. — H2Mg2Si207+aq.  Silesia.  LIMBACHITE  from  Limbach,  and  ZOBLITZITB 
from  Zoblitz,  are  varieties  of  cerolite. 

GENTHITE.     Nickel-Gymnite. 

Amorphous,  with  a  delicately  hemispherical  or  stalactitic  surface,  in- 
erusting. 

H.  =  3-4:;  sometimes  (as  at  Michipicoten)  so  soft  as  to  be  polished 
under  the  nail,  and  fall  to  pieces  in  water.  G.= 2-409.  Lustre  resinous. 
Color  pale  apple-green,  or  yellowish.  Streak  greenish- white.  Opaque  to 
translucent. 

Comp. — Q.  ratio  for  R  :  Si  :  H=2  :  3  :  3,  or  the  same  as  for  deweylite  ;  formula  H4(Ni, 
Mg^SigOia,  being  a  nickel-gymnite.  Analysis:  Genth,  Texas,  Pa.,  SiO2  35 '36,  NiO  30'04, 
FeO  0-24,  MgO  14 -60,  CaO  0'26,  H20  19-09=100-19. 

Pyr.,  etc. — In  the  closed  tube  blackens  and  gives  off  water.  B.  B.  infusible.  With  borax 
inO.F.  gives  a  violet  bead,  becoming  gray  in  R.F.  (Nickel).  Decomposed  by  hydrochloric 
acid  without  gelatinizing. 

Obs. — From  Texas,  Lancaster  Co. ,  Pa. ,  in  thin  crusts  on  chromic  iron  ;  from  Webster, 
Jackson  Co.,  N.  C.;  on  Michipicoten  Id.,  Lake  Superior. 

ALIPITE  and  PIMELITE,  an  apple-green  silicates  containing  some  nickel.  GARNIERITE 
and  NOUMEITE,  from  New  Caledonia  are  similar,  aud  have  been  shown  by  Liversidge  to  be 
mixtures. 


Kaolinite  Group. 

KAOLINITE. 

Orthorhombic.  /A  f=  120°.  In  rhombic,  rhomboidal,  or  hexagonal 
scales  or  plates  ;  sometimes  in  fan-shaped  aggregations  ;  usually  constitut- 
ing a  clay -like  mass,  either  compact,  friable,  or  mealy  ;  base  of  crystals 
lined,  arising  from  the  edges  of  superimposed  plates.  Cleavage  :  basal, 
perfect.  Twins :  the  hexagonal  plates  made  up  of  six  sectors. 

H.=:  1-2-5.  G-.  =  2-4-2-63.  Lustre  of  plates  pearly;  of  mass,  pearly  to 
dull  earthy.  Color  white,  grayish-white,  yellowish,  sometimes  brownish, 
bluish,  or  reddish.  Scales  transparent  to  translucent.  Scales  flexible, 
inelastic;  usually  unctuous  and  plastic. 

Var. — 1.  Argilliform.  Soft,  clay-like  ;  ordinary  kaolinite  ;  under  the  microscope,  if  not 
without,  showing  that  it  is  made  up  largely  of  pearly  scales.  The  constituent  of  most,  if  not 


330  DESCRIPTIVE   MINERALOGY. 

all,  pure  kaolin.  2.  Fariniform.  Mealy,  hardly  coherent,  consisting  of  pearly  angular 
scales.  3.  Indurated;  Lithomarge  (Steinmark,  Germ.).  Firm  and  compact;  H.=2-2'5. 
When  pulverized,  often  shows  a  scaly  texture. 

Comp. — Q.  ratio  for  ft  :  Si  :  H=3  :  4  :  2  ;  formula  AlSi2O7+2aq,  or  making  part  of  the 
water  basic,  H2AlSi2O8+aq=Siiica  464,  alumina  39 '7,  water  13-9  =  100. 

Pyr.,  etc.— Yields  water.  B.B.  infusible.  Gives  a  blue  color  with  cobalt  solution.  Insol- 
uble in  acids. 

Diff. — Characterized  by  its  unctuous,  soapy  feel ;  alumina  reaction  B.B. 

Obs. — Ordinary  kaolin  is  a  result  of  the  decomposition  of  aluminous  minerals,  especially 
the  feldspars  of  granitic  and  gneissoid  rocks  and  porphyries.  In  some  regions  where  these 
rocks  have  decomposed  on  a  large  scale,  the  resulting  clay  remains  in  vast  beds  of  kaolin, 
usually  more  or  less  mixed  with  free  quartz,  and  sometimes  with  oxide  of  iron  from  some  of 
the  other  minerals  present. 

Occurs  at  Cache-Apres  in  Belgium  ;  also  in  Bohemia ;  in  Saxony.  At  Yrieix,  near  Limoges, 
is  the  best  locality  of  kaolin  in  Europe,  it  affords  material  for  the  famous  Sevres  porcelain 
manufactory. 

In  the  U.  States,  kaolin  occurs  at  Newcastle  and  Wilmington,  Del. ;  at  various  localities  in 
the  limonite  region  of  Vermont  (at  Branford,  etc.) ;  Massachusetts  ;  Pennsylvania ;  Jackson- 
ville, Ala.;  Edgefield,  S.  C.;  near  Augusta,  Ga. 

PIIOLERITE,  HALLOYSITE,  clays  allied  to  kaolinite. 

SAPCXNITE. — A  soft  magnesian  silicate  ;  occurs  in  cavities  in  trap. 


Pinite  Group. 

FINITE. 

Amorphous  ;  granular  to  cryptocrystalline  ;  usually  the  latter.  Also  in 
crystals,  and  sometimes  with  cleavage,  but  only  because  pseudomorphs,  the 
form  and  cleavage  being  those  of  the  minerals  from  which  derived.  Barely 
a  sub  micaceous  cleavage,  which  may  belong  to  the  species. 

H.=2'5-3'5.  Gr.=2'6— 2*85.  Lustre  feeble,  waxy.  Color  grayish-white, 
grayish-green,  pea-green,  dull  green,  brownish,  reddish.  Translucent — 
opaque.  Acts  like  a  gum  on  polarized  light  j  DesCl. 

Comp.,  Var. — Pinite  is  essentially  a  hydrous  alkaline  silicate.  Being  a  result  of  alteration, 
and  amorphous,  the  mineral  varies  much  in  composition,  and  numerous  species  have  been 
made  of  the  mineral  in  its  various  conditions.  The  varieties  of  pinite  here  admitted  agree 
closely  in  physical  characters,  and  in  the  amount  of  potash  and  water  present.  Average  com- 
position :  Silica  46,  alumina  30,  potash  10,  water  6  ;  formula  (Ramm.)  H6K2Al.2Si5O2o.  The 
mineral  is  related  chemically,  as  it  is  also  physically,  to  serpentine  ;  and  it  is  an  alkali-alumina 
serpentine,  as  pyrophyllite  is  an  alumina  talc. 

The  different  kinds  are  either  pseudomorphous  crystals  after  (1)  iolite  ;  (2)  nephelite  ;  (3) 
scapolite ;  (4)  some  kind  of  feldspar ;  (5)  spodumene  ;  or  (6)  other  aluminous  mineral ;  or  ( 7) 
disseminated  masses  resembling  indurated  talc,  steatite,  lithomarge,  or  kaolinite,  also  a  result 
of  alteration  ;  or  (8)  the  prominent  or  sole  constituent  of  a  metamorphic  rock,  which  is  some- 
times a  pinite  schist  (analogous  to,  and  often  much  resembling,  talcose  schist,  and  still  more 
closely  related  to  pyrophyttite  sc7iist).  Some  prominent  varieties  are  : 

PINITE.  Speckstein  [fr.  the  Pini  mine  at  Aue,  near  Schneeberg].  Occurs  in  granite,  and 
is  supposed  to  be  pseudomorphous  after  iolite. 

GIESECKITE.  In  6-sided  prisms,  probably  pseudomorphous  after  nephelite.  H=3  5. 
G.  =2 '78-2 '85.  Color  grayish-green,  olive-green,  to  brownish.  Brought  by  Giesecke  from 
Greenland.  Also  of  similar  characters  from  Diana,  N.  Y. 

AGALMATOLITE.  Like  ordinary  massive  pinite  in  its  amorphous  compact  texture,  lustre, 
and  other  physical  characters,  but  contains  more  silica,  so  as  to  afford  the  formula  of  a  bisili- 
cate,  or  nearly,  and  it  may  be  a  distinct  species.  Agalmato'Me  was  named  from  oyaA/^a,  an 
image,  and  pagodite  from  pagoda,  the  Chinese  carving  the  soft  stone  into  miniature  pagodas, 


OXYGEN   COMPOUNDS HYDKOUS    SILICATES.  331 

images,  etc.     Part  of  the  so-called  agalmatolite  of  China  is  true  pinite  in  composition,  another 
part  is  compact  pyrophyllite  (p.  327),  and  still  another  steatite  (p.  326). 

Other  minerals  belonging  in  or  near  the  pinite  group  are  :  dyssyntribite  (=gieseckite)  ; 
parophite;  icilsonite;  polyargite;  rosite  ;  Mllinite  ;  gigantolite ;  hygropJiiiite  ;  gumbelite  j 
restwmetite.  Also  cataspilite  ;  biharite  ;  palagonite. 


Hydro-mica  Group. 

FAHLUNITE. 

In  six-  or  twelve-sided  prisms,  but  derived  from  pseudomorphism  after 
iolite.  Cleavage  :  basal  sometimes  perfect. 

H.=3'5-5.  G.=2'6-2*8.  Lustre  of  surface  of  basal  cleavage  pearly  to 
waxy,  glimmering.  Color  grayish-green,  to  greenish-brown,  olive-  or  oil- 
green  5  sometimes  blackish-green  to  black  ;  streak  colorless. 

Var. — This  species  is  a  result  of  alteration,  and  considerable  variation  in  the  results  of 
analyses  should  be  expected.  The  crystalline  form  is  that  of  the  original  iolite,  while  the 
basal  cleavage  when  distinct  is  that  of  the  new  species  fahlunite. 

Comp. — Q.  ratio  f  or  R  :  R  :  Si  :  H=l  :  3  :  5  :  1 ;  whence  the  formula  H4RoRoSi5p2o,  the 
water  being  considered  as  basic,  and  as  entering  to  make  up  the  deficiency  of  bases  in  the 
unisilicate.  In  some  kinds,  the  same  with  the  addition  of  H2O.  The  Q.  ratio  of  iolite,  the 
original  of  the  species,  is  1:3:5.  Analysis  by  Wachtmeister,  from  Fahlun,  SiO2  44-60, 
A103  30-10,  FeO  3'86,  MnO  2'24,  MgO  6 '75,  CaO  1-35,  K2O  IDS,  H2O  9'35,  F  tr=100-23. 

Pyr.,  etc. — Yields  water.  B.B.  fuses  to  a  white  blebby  glass.  Not  acted  upon  by  acids. 
Pyrargillite  is  difficultly  fusible,  but  is  completely  decomposed  by  hydrochloric  acid. 

Obs. — Fahlunile  (and  trida&ite)  from  Fahlun,  Sweden.  The  following  are  identical,  or 
nearly  so  :  Esmarkite  and  praseolite,  Brevig;  raumite,  Raumo,  Finland;  chlorophyllite,  Unity, 
Me.  ;  pyrargttlite,  Helsingfors ;  polychroilite,  Krageroe,  and  aspasiolite,  Norway ;  huronite, 
Lake  Huron  (  Weissite,  Fahlun). 


MARGARODITE. 

Like  muscovite  or  common  mica  in  crystallization,  and  in  optical  and 
other  physical  characters,  except  usually  a  more  pearly  lustre,  and  the  color 
more  commonly  whitish  or  silvery. 

Comp.— Q.  ratio  for  R  :  R  :  Si  :  H  mostly  1:6:9:2;  whence  the  formula  HeR2A-l4Si9O36, 
the  water  being  basic.  Sometimes  Q.  ratio  1  :  9  :  12  :  2;  but  this  division  belongs  with 
damourite,  if  the  two  are  distinguishable.  This  species  appears  to  be  often,  if  not  always,  a 
result  of  the  hydration  of  muscovite,  there  being  ail  shades  of  gradation  between  it  and  that 
species.  Muscovite  has  the  Q.  ratio  for  bases  and  silicon  of  4  :  5,  or  nearly.  Analysis,  Smith 
and  Brush,  Litchfield,  Ct.,  SiO2  44 "60,  Al  36-23.  FeO  1'34,  MgO  0'37,  CaO  0'50,  Na*O  410, 
K.,O  6-20,  H2O  5-26,  F  tr.  =  100-60. 

For  pyrognostics  and  localities,  see  muscovite,  p.  291. 

GILBERTITE. — Essentially  identical  with  margarodite  ;  tin  mines,  Saxony. 


DAMOURITE. 

An  aggregate  of  fine  scales,  mica-like  in  structure. 

H.  =  2-3.     G.  =  2*792.     Lustre  pearly.     Color  yellow  or  yellowish- white. 
Optic-axial  divergence  10  to  12  degrees  ;  for  sterlingite  70°. 

Comp. — A  hydrous  potash-mica,  like  margarodite,  to  which  it  is  closely  related.     Q.  ratio 


332  DESCRIPTIVE   MINERALOGY. 

for  R  :  ft  :  Si  :  H=l  :  9  :  12  :  2,  or  1  :  1  for  bases  to  silicon,  if  the  water  is  basic.  Formula 
H4K2Al3Si6O24.  Analysis,  Monroe,  from  Sterling,  Mass,  (sterlingite) ,  Si02  43'87,  A1O3  30 '45, 
Fe03  3-36,  K2O  10'86,  H2O  519=99-73. 

It  is  the  gangue  of  cyaiiite  at  Pontivy  in  Brittany;  and  the  same  at  Horrsjoberg.  Werm- 
iand.     Associated  with  corundum  in  North  Carolina ;  with  spodumene,  at  Sterling,  Mass. 


PARAGONITE.     Pregrattite.     Cossaite. 

Massive,  sometimes  consisting  distinctly  of  fine  scales ;  the  rock  slaty  or 
schistose.  Cleavage  of  scales  in  one  direction  eminent,  mica-like. 

H.=2-5-3.  Gr. = 2*779,  paragoirite;  2-895,  pregrattite,  (Ellacher.  Lustre 
strong  pearly.  Color  yellowish,  grayish,  grayish- white,  greenish,  light  apple- 
green.  Translucent ;  single  scales  transparent. 

i 

Comp. — A  hydrous  sodium  mica.  Q.  ratio  for  R  :  R  :  Si  :  H—l  :  9  :  12  :  2,  or  1  :  1  for 
bases  and  silicon,  if  the  water  be  made  basic.  Formula  H4NaoAl3SieO24(K  :  Na=l  :  6)  = 
Silica  46-60,  alumina  39-96,  soda  6 "90,  potash  174,  water  4-80=100. 

Pyr. — B.B.  the  paragonite  is  stated  to  be  infusible.  The  pregrattite  exfoliates  somewhat 
like  vermiculite  (a  property  of  some  clinochlore  and  other  species),  and  becomes  milk-white 
on  the  edges. 

Obs. — Paragonite  constitutes  the  mass  of  the  rock  at  Monte  Campione,  in  the  region  of 
St.  Gothard,  containing  cyanite  and  staurolite,  called  paragonitic  or  talcose  schist.  The 
pregrattite  is  from  Pregratten  in  the  Pusterthal,  Tyrol ;  cossaite,  from  mines  of  Borgofranco, 
near  Ivrea. 

IVIGTITE. — Occurs  in  yellow  scales,  also  granular,  with  cryolite  from  Greenland. 

EUPHYLLITE. — Associated  with  tourmaline  and  corundum  at  Union ville,  Penn.  Q.  ratio 
for  R:R:Si:Hi=l:8:9:2.  Average  composition,  Silica  41-6,  alumina  42-3,  lime  1*5, 
potash  3 '2,  soda  5-9,  water  5-o  =  100. 

EPHESITE,  LESLEYITE. — Hydro- micas,  perhaps  identical  with  damourite.  Occur  with 
corundum,  and  impure  from  admixture  with  it. 

(ELLACHERITE. — A  hydro-mica,  containing  5  p.  c.  baryta.     Pfitschthal,  Tyrol. 

COOKEITE. — A  hydrous  lithium  mica.  From  Hebron  and  Paris,  Me.,  apparently  a  pro- 
duct of  the  alteration  of  rubellite. 


HISINGERITE. 

Amorphous,  compact,  without  cleavage. 

H.  =  3.  Gr.— 3-04:5.  Lustre  greasy,  inclining  to  vitreous.  Color  black 
to  brownish-black.  Streak  yellowish-brown.  Fracture  conchoidal. 

Comp. — Q.  ratio  for  R+R  :  Si  :  H=2  :  3  :  3  ;  formula  RGR2Si3Oi8+4aq  (with  one-third 
of  the  water  basic).  R=Fe,H2;  R=Fe.  Analysis,  Cleve,  from  Solberg,  Norway,  Si02  35'33, 
FeO3  32-14,  FeO  7-08,  MgO  3'60,  H~2O  22-04=100-19. 

Pyr.,  etc. — Yields  much  water.  B.B.  fuses  with  difficulty  to  a  black  magnetic  slag.  With 
the  fluxes  gives  reactions  for  iron.  In  hydrochloric  acid  easily  decomposed  without  gelatin- 
izing. 

Obs.— Found  at  Longban,  Tunaberg,  Sweden ;  Riddarhyttan  ;  at  Degero  (degerdite),  near 
Helsingfors,  Finland. 

EKMANNITE. — Foliated,  also  radiated.  Color  green,  resembles  chlorite.  Analysis,  Igel- 
strom,  SiO2  34'30,  Fe03  4'97,  FeO  35'7S,  MnO  11'45,  MgO  2-99,  H20  10'51=100.  With 
magnetite  at  Grythyttan,  Sweden. 

NEOTOCITE. — Uncertain  alteration-products  of  rhodonite ;  amorphous.  Contains  20-30 
p.  c.  MnO.  Paisberg,  near  Filipstadt,  Sweden ;  Finland,  etc. 

GILLINGITE  ;  Sweden.     JOLLYTE  ;  Bodenmais,  Bavaria. 


OXYGEN   COMPOUNDS HYDKOUS    SILICATES.  333 


Vermiculite  Group. 

The  VEEMICULITES  have  a  micaceous  structure.  They  are  all  unisilicates, 
having  the  general  quantivalent  ratio  K-j-R  :  Si  :  11=2  :  2  :  1,  the  water 
being  solely  water  of  crystallization.  The  varieties  differ  in  the  ratio 
of  the  bases  present  in  the  protoxide  and  sesquioxide  states.* 


JEFFERISITE. 

Orthorhombic  (?).  In  broad  crystals  or  crystalline  plates.  Cleavage :  basal 
eminent,  affording  easily  very  thin  folia,  like  mica.  Surface  of  plates  often 
triangularly  marked,  by  the  crossing  of  lines  at  angles  of  60°  and  120°. 

JL=1'5.  G-.=2*30.  Lustre  pearly  on  cleavage  surface.  Color  dark 
yellowish-brown  and  brownish-yellow ;  light  yellow  by  transmitted  light. 
Transparent  only  in  very  thin  folia.  Flexible,  almost  brittle.  Optically 
biaxial ;  DesCl.  * 

Comp.— Q.  ratio  for  R  :  R  :  Si  :  H=2  :  3  :  5  :  2£,  and  R  +  R  :  Si  :  IL-.2  :  2  :  1  ;  whence 
R4R2Si502o+5aq.  Analysis:  Brush,  Westchester,  BiO,  3710,  A103  17'57,  Fe03  10'54,  FeO 
1-26,  MgO  19-65,  CaO  0'56,  Na,O  tr.,  K2O  0'43,  H2O  13-76=100'87. 

Pyr.,  etc.— When  heated  to  300°  C.  exfoliates  very  remarkably  (like  vermiculite)  ;  B.B.  in 
forceps  after  exfoliation  becomes  pearly-white  and  opaque,  and  ultimately  fuses  to  a  dar-c 
gray  mass.  With  the  fluxes  reactions  for  silica  and  iron.  Decomposed  by  hydrochloric  acid. 

Obs. — Occurs  in  veins  in  serpentine  at  Westchester,  Pa.     Plates  often  several  inches  across. 

PTROSCLEKITE.—  Q.  ratio  for  R  :  ft  :  Si  :  H=4  :  2  :  6  :  3,  and  for  R+R  :  Si  :  H=2  :  2  :  1. 
Silica  38-9,  alumina  14-8,  magnesia  34'6,  water  11-7=100.  Color  green.  Elba.  CHONICRITE, 
also  Elba,  has  the  ratio  3:2:5:2. 

VERMICULITE. — Q.  ratio  for  R  :  R  :  Si  :  H=4  :  2  :  6  :  3.  Milbury,  Mass.  CULSAGEEITE. 
Q.  ratio  R  :  ft  :  Si  :  H=2  :  1  :  1  :  1.  Jenk's  mine,  N.  C.  HALLITE,  same  ratio=2  :  1  :  3  :  2. 
East  Nottingham,  Chester  Co.,  Penn.  PELIIAMITE,  same  ratio=6  :  4  :  10  :  5.  Pelham, 
Mass.  Similar  mineral  from  Lerni,  Delaware  Co.,  Pa.,  above  ratio=6  :  4  :  10  :  5.  In  all  of 
the  above  R=Mg  mostly,  and  R=A1  and  Fe. 

KEKRITE. — Q.  ratio=6  :  3  :  10  :  10 ;  and  MACONITE,  Q.  ratio=3  :  6  :  8  :  5,  are  both  from 
Culsagee  mine,  Macon  Co.,  N.  C.  VAALITE,  Q.  ratio=6  :  3  :  10  :  4.  South  Africa. 

DIABANTITE,  Hawes  (diabantachronnyn,  Liebe). — Fills  cavities  in  amygdaloidal  trap. 
Color  dark  green.  Q.  ratio  for  R  :  ft  :  Si  :  H=4  :  2  :  6  :  3,  but  iron  a  more  prominent  ingre- 
dient than  in  pyrosclerite  (see  above).  Analysis  :  Hawes,  Farmington,  Ct.,  I  SiO2  33 '68,  A1O3 
10-84,  Fe03  2-86,  FeO  24-33,  MnO  0'38,  CaO  0'73,  MgO  16'52,  Na20  0-33,  H2O  10'-02=99-69. 


SUBSILICATES. 

Chlorite  Group. 
PENNINITE.    Kammererite. 

Ehombohedral.  R  A  R  =  65°  36',  O  A  R  =  103°  55  ;  c  =  3-4951. 
Cleavage ;  basal,  highly  perfect.  Crystals  often  tabular,  and  in  crested 
groups.  Also  massive,  consisting  of  an  aggregation  of  scales ;  also  com- 
pact cryptocry  stall  in  e. 

*  These  relations  were  brought  out  by  Cooke.  Proc.  Amer.  Acad.,  Boston,  1874,  35  ; 
ibid.,  1875,  453, 


334. 


DESCRIPTIVE   MINERALOGY. 


II.  —  2-2-5  ;  3,  at  times,  on   edges. 


652 


653 


G. =2-6-2-85.  Lustre  of  cleavage 
surface  pearly  ;  of  lateral  plates 
vitieous,  and  sometimes  brilliant. 
Color  green,  apple-green,  grass- 
green,  grayish-green,  olive-green; 
also  reddish,  violet,  rose-red, 
pink,  grayish-red ;  occasionally 
yellowish  and  silver- white;  violet 
crystals,  and  sometimes  the 
green,  hyacinth-red  by  trans- 
mitted light  along  the  vertical 

axis.  Transparent  to  snbtranslucent.  Laminae  flexible,  no!:  elastic.  Double 
refraction  feeble  ;  axis  either  negative  or  positive,  and  sometimes  positive, 
and  negative  in  different  laminge  of  the  same  plate  or  crystal. 

Comp. — Q.  ratio  for  bases  and  silicon  4:3,  but  varying  from  4  :  3  to  5  :  4.  Exact  deduc- 
tions from  the  analyses  cannot  be  made  until  the  state  of  oxidation  of  the  iron  in  all  cases  is 
ascertained.  Analysis:  Schweizer,  from  Zermatt,  Si02  33'07,  A1O3  9-69,  FeO  11 '36,  MgO 
32-34,  H2O  12-58=99-08. 

t  Pyr.,  etc. — In  the  closed  tube  yields  water.  B.B.  exfoliates  somewhat  and  is  difficultly 
fusible.  With  the  fluxes  all  varieties  give  reactions  for  iron,  and  many  varieties  react  for 
chromium.  Partially  decomposed  by  acids. 

Obs. — Occurs  with  serpentine  in  the  region  of  Zermatt,  Valais,  near  Mt.  Rosa  ;  at  Ala, 
Piedmont ;  at  Schwarzenstein  in  the  Tyrol ;  at  Taberg  in  Wermland  ;  at  Snarum.  Kam- 
mererite  is  found  near  Miask  in  the  Urals;  at  Haroldswick  in  Unst,  Shetland  Isles.  Abun- 
dant at  Texas,  Lancaster  Co.,  Pa.,  along  with  clinochlore,  some  crystals  being  imbedded  in 
clinochlore,  or  the  reverse. 

The  following  names  belong  here  :  tabergite ;  pscudopMte,  compact,  massive  (allopJdte^ ; 
loganite. 

Delessite,  euralite,  aphrosiderite,  cJiloropJiczite  are  chloritic  minerals,  occurring  under  simi- 
lar conditions,  in  amygdaloid,  etc. 


RIPIDOLITE.     Clinochlore.     Klinochlor,  Germ. 


Monoclinic.     O=  62C 


654 


51'=O/\i-i,  /A  7=125°  37',  (9  A  44  =  108° 
14' :  c  :  I  :  d  =  1-47756  : 
1-73195  :  1.  Cleavage  :  O 
eminent ;  crystals  often  tab- 
ular, also  oblong ;  frequent- 
ly rhombohedral  in  aspect, 
the  plane  angles  of  the 
base  being  60b  and  120°. 
Twins:  twinning-plane  3? 
making  stellate  groups,  as  in 
f.  656,  657,  very  common. 
Crystals  often  grouped  in 
rosettes.  Massive  coarse  scaly 
granular  to  fine  granular  and 

Achmatovsk.  Achmatovsk.  earthy. 

H.=2-2-5.  G.=2-65-2-78. 

Lustre  of  cleavage-face  somewhat  pearly.  Color  deep  grass-green  to  olive- 
green  ;  also  rose-red.  Often  strongly  dichroic.  Streak  greenish-white  to 
uncolored.  Transparent  to  translucent.  Flexible  and  somewhat  elastic. 


OXYGEN   COMPOUNDS — HYDEOUS    SILICATES. 


335 


l  l 
Westchester. 


Comp.  —  Q.  ratio  for  R  :  ft  :  Si  :  H=5  :  3  :  6  :  4  ;  corresponding  to  Mg5AlSi3Oi4 
Silica  32'5,    alumina  18  '6,    magnesia  3(5  '0, 
water  12-9—  100.     Sometimes  part  of  the  Mg 
is  replaced  by  Fe. 

Pyr.,  etc.—  Yields  water.  B.B.  in  the 
platinum  forceps  whitens  and  fuses  with 
difficulty  on  the  edges  to  a  grayish-black 
glass.  With  borax  a  clear  glass  colored  by 
iron,  and  sometimes  chromium.  In  sul- 
phuric acid  wholly  decomposed.  The  variety 
from  Willimantic,  Ct.,  exfoliates  in  worm- 
like  forms,  like  vermicuiite. 

Obs.  —  Occurs  in  connection  with  chloritic 
and  talcose  rocks  or  schist,  and  serpentine. 
Found  at  Achmatovsk  ;  Schwarzenstein  ; 
Zillerthal,  etc.  ;  red  (kotschubeite)  in  the  dis- 
trict of  Ufaleisk.  Southern  Ural;  at  Ala,  Piedmont;  at  Zermatt  ;  at  Marienberg,  Saxony. 
In  the  U.  S.  ,  at  Westchester  and  Unionville,  and  Texas,  Pa.  ;  Brewster,  N.  Y. 

Named  ripidolite  from  pnng,  a  fan,  in  allusion  to  a  common  mode  of  grouping  of  the  crys- 
tals. 

LEUCIITENBERGITE.  —  A  prochlorite  with  the  protoxide  base  almost  wholly  magnesia. 
SJatoust,  Urals. 

PROCHLORITE. 

Hexagonal  (?).      Cleavage  :  basal,  eminent.     Crystals  often  implanted  by 
their  sides,  and  in  divergent  groups,  fan-shaped,  or 
spheroidal.     Also  in  large  folia.     Massive  granular. 

II.  =  1-2.  G.  =  2'78-2-96.  Translucent  to  opaque  ; 
transparent  only  in  very  thin  folia.  Lustre  of 
cleavage  surface  feebly  pearly.  Color  green, 
grass-green,  olive-green,  blackish-green  ;  across  the 
axis  by  transmitted  light  sometimes  red.  Streak 
uncolored  or  greenish.  Laminae  flexible,  not  elastic. 
Double  refraction  very  weak  ;  one  optical  negative 
axis  (Dauphiny)  ;  or  two  very  slightly  diverging,  apparently 
plane  of  cleavage. 

Comp.—  Q.  ratio  f  or  R  :  ft  :  Si  :  H=12  :  9  :  14  :  91  ;  for  bases  and  silicon  3  :  2.  Average 
compositi  on  =  Silica  26  '8,  alumina  19  "7,  iron  protoxide  27  "5,  magnesia  15  '3,  water  10  '7=100. 

Pyr.,  etc.  —  Same  as  for  ripidolite. 

Obs.  —  Like  other  chlorites  in  mode  of  occurrence.  Sometimes  in  implanted  crystals,  as  at 
St.  G-othard,  etc.  ;  in  the  Zillerthal,  Tyrol;  Traversella  in  Piedmont;  in  Styria,  Bohemia. 
Also  massive  in  Cornwall,  in  tin  veins  (where  it  is  called  peach]  ;  at  Arendal  in  Norway. 

CRONSTEDTITE.  —  Q.  ratio  R  :  ft  :  Si  :  H=3  :  3  :  4  :  3.     Przibram;  Cornwall. 

STKIGOVITE.  —  Q.  ratio=3  :  2  :  4  :  2.  In  granite  of  Striegan,  Silesia.  GROCHAUITE  same 
locality. 


normal   to 


MARGARITB.    Perlglimmer,  Germ. 


/A/=  119°- 


Orthorhombic  (?) ;  hemihedral,  with  a  monoclinic  aspect. 
120°.  Lateral  planes  horizontally  striated.  Cleavage : 
basal,  eminent.  Twins:  common,  composition-face 
/,  and  forming,  by  the  crossing  of  3  crystals,  groups 
of  6  sectors.  Usually  in  intersecting  or  aggregated 
laminae  ;  sometimes  massive,  with  a  scaly  structure. 

H.=3-5^4:-5.  G.=2-99,  Hermann.  Lustre  of 
base  pearly,  laterally  vitreous.  Color  grayish,  red- 
dish-white, yellowish.  Translucent,  subtranslucent.  Laminoe  rather  brittle. 


336  DESCRIPTIVE   MINERALOGY. 

Optic-axial  angle  very  obtuse  ;  plane  of  axes  parallel  to  the  longer  diagonal ; 
dispersion  feeble. 

Comp. — Q.  ratio  for  R  :  R  :  Si  :  H=l  :  6  :  4  :  1  ;  whence,  if  the  water  be  basic,  for  bases 
and  silicon =2  :  1,  f  ormula  RRSiO5 ;  that  is,  H2Cartl2SioOi2.  Analysis,  Smith,  Chester,  Mass., 
Si03  32-21,  A1O3  48-87,  Fe03  2-50,  MgO  0'32,  CaO  10'02,  Na2O(K2O)  1-91,  H,O  4 '61,  Li2O 
0-32,  MnO  0-20=100-96. 

Pyr.,  etc. — Yields  water  in  the  closed  tube.     B.B.  whitens  and  fuses  on  the  edges. 

Obs. — Margarite  occurs  in  chlorite  from  the  Greiner  Mts. ;  near  Sterzing  in  the  Tyrol ;  at 
different  localities  of  emery  in  Asia  Minor  and  the  Grecian  Archipelago ;  with  corundum  in 
Delaware  Co.,  Pa.;  at  Unionville,  Chester  Co.,  Pa.  (corunddlite} ;  in  Madison  Co.  (cling- 
manite),  and  elsewhere  in  North  Carolina  ;  at  the  emery  mines  of  Chester,  Mass. 


.  CHLORITOID. 

Monoclinic,  or  triclinic.  /A  I'  about  100°  ;  0  (or  cleavage  surface)  on 
lateral  planes  93°-95°,  DesCl.  Cleavage :  basal  perfect ;  parallel  to  a 
lateral  plane  imperfect  Usually  coarsely  foliated  massive ;  folia  often 
curved  or  bent,  and  brittle;  also  in  thin  scales  or  small  plates  disseminated 
through  the  containing  rock. 

H.  =  5'5-6.  GK=&'5-3'6.  Color  dark  gray,  greenish-gray,  greenish- 
black,  grayish-black,  often  grass-green  in  very  thin  plates  ;  strongly  dichroic. 
Streak  uncolored,  or  grayish,  or  very  slightly  greenish.  Lustre  of  surface 
of  cleavage  somewhat  pearly.  Brittle. 

Var. — 1.  The  original  chloritoid  (or  chloritspath)  from  Kossoibrod,  near  Katharinenburg  in 
the  Ural.  2.  The  Sismondine,  from  St.  Marcel.  3.  Masonite,  from  Natic,  R.  I.,  in  very 
broad  plates  of  a  dark  grayish-green  color.  The  Canada  mineral  is  in  small  plates,  one-fourth 
in.  wide  and  half  this  thick,  disseminated  through  a  schist  (like  phyllite),  and  also  in  nodules 
of  radiated  structure,  half  an  inch  through.  That  of  Gumuch-Dagh  resembles  sismondine,  is 
dark  green  in  thick  folia  and  grass-green  in  very  thin. 

Comp.— Q.  ratio  for  R  :  ft  :  Si  :  H— 1  :  3  :  2  :  1,  for  most  analyses.  Analysis  by  v.  Kobell, 
Bregratten,  SiOa  26'19,  A1O3  38'30,  FeO3  6  "00,  FeO  2111,  MgO  3'30,  H2O  5 -50=100-40. 

Pyr.,  etc  — In  a  matrass  yields  water.  B.B.  nearly  infusible  ;  becomes  darker  and  magne- 
tic. Completely  decomposed  by  sulphuric  acid.  The  masonite  fuses  with  difficulty  to  a  dark 
green  enamel. 

Obs. — The  Kossoibrod  chloritoid  is  associated  with  mica  and  cyanite  ;  the  St.  Marcel  occurs 
in  a  dark  green  chlorite  schist,  with  garnets,  magnetite,  and  pyrite  ;  the  Rhode  Island,  in  an 
argillaceous  schist ;  the  Chester,  Mass. ,  in  talcose  schist,  with  emery,  diaspore.  etc. 

Phyllite  (and  ottrelite)  closely  resembles  chloritoid,  though  the  analyses  hitherto  made  show 
a  wide  discrepancy,  perhaps  from  want  of  purity  in  the  material  analyzed.  Occurs  in  small, 
oblong,  shining  scales  or  plates,  in  argillaceous  schist.  Color  blackish  gray,  greenish-gray, 
black.  Phyllite  occurs  in  the  schist  of  Sterling,  Goshen,  Chesterfield,  Plainfield,  etc.,  in 
Massachusetts,  and  Newport,  R.  I.  (newportite).  Ottrelite  is  from  a  similar  rock  near  Ottrez. 

SEYBERTITE. — Orthorhombic.  I A  2=  120°.  In  tabular  crystals,  sometimes  hexagonal; 
also  foliated  massive  ;  sometimes  lamellar  radiate.  Cleavage  :  basal  perfect.  Structure  thin 
foliated,  or  micaceous  parallel  to  the  Taase.  H.  =4-5.  G.  =3-3-1.  Lustre  pearly  sub  metallic. 
Color  reddish-brown,  yellowish,  copper-red.  Folia  brittle.  Analysis,  Brush,  Amity,  SiO2 
20-24,  AlOs  39-13,  FeO3  3"27,  Mg020'84,  CaO  13'69,  H20  1'04,  Na2O(K20)  1'43,  Zr020-75  = 
100 '39.  Amity,  N.  Y.  (dintonite) ;  Fassathal  (brandisite);  Slatoust  (xanthophyllite}. 

CORUNDOPHILITE. — A  chlorite  with  the  Q.  ratio=l  :  1  :  1  :  {j- .  Occurs  with  corundum  at 
Asheville.  N.  C.;  Chester,  Mass. 

DTTDLEYITE. — Alteration  product  of  margarite.     Clay  Co.,  N.  C. ;  Dudleyville,  Ala. 

WIL.LCOXITE. — Near  margarite.  Decomposition  product  of  corundum.  Q.  ratio  for  R  :  R  : 
Si  :  H=3  :  6  :  5  :  1. 

TIIUIUNGITE. — Q.  ratio  2:3:3:2.  Contains  principally  iron  (Fe  and  Fe).  Hot  Springs, 
Arkansas;  Harper's  Ferry  (owenite).  Pattersonite  from  Unionville,  Pa.,  near  thuringite. 


OXYGEN    COMPOUNDS. — TANTALATES,   COLUMBATES. 


337 


2.   TANTALATES,   COLUMBATES. 


PYROCHLORE. 

Isometric.  Commonly  in  octahedrons.  Cleavage:  octahedral,  some- 
times distinct,  especially  in  the  smaller  crystals. 

II.  =  5-5 '5.  G.= 4-2-4-35.  Lustre  vitreous  or  resinous.  Color  brown, 
dark  reddish-  or  blackish-brown.  Streak  light  brown,  yellowish-brown. 
Subtranslucent — opaque.  Fracture  conchoidal. 

Comp. — A  columbate  of  calcium,  cerium,  and  other  bases  in  varying  amounts.  Analysis, 
by  Rammelsberg,  Brevig,  Cb205  58 -27,  TiOa  5 -38,  ThO2  4 '96,  CeO  5  -50,  CaO  10 -93,  FeO;U02) 
5-53,  Na2O  5 '31,  F  3 "75,  H2O  1-53  =  101-16. 

Obs.— Occurs  in  syenite  at  Friederichsvarn  and  Laurvig,  Norway;  at  Brevig;  near  Miask 
in  the  TJraJs  ;  Kaiserstuhlgebirge  in  Breisgau  (koppite) ;  with  samarskite  in  N.  Carolina  (G-.— 
4' 794,  chemical  character  unknown). 

MICROLITE. — In  minute  yellow  octahedrons  in  feldspar.  G.=5'5.  Near  pyrochlore,  bub 
probably  containing  more  tantalum  pentoxide.  Chesterfield,  Mass. 

PYRRIIITE. — In  isometric  octahedrons.  Color  orange -yellow.  Chemical  character  un- 
known. From  Mursinsk  in  the  Ural.  A  mineral  supposed  to  be  similar  from  the  Azores 
contains  essentially,  according  to  Hayes,  columbium,  zirconium,  etc. 

AZORITE. — In  minute  tetragonal  octahedrons  resembling  zircon.  From  the  Azores  in  albite. 
Chemical  character  unknown. 


TANTALITE. 

Orthorhombic.     Observed   planes   as   in    the   figure. 
O  A  l-l  =  122°  3i'  ;  c\l\a  =  1-5967  :  1-53247  :  1.      0  A 
f-2  =  117°  2',  i-l  A  1-2  =  143°  6i',  1-5  A  1-2,  adj.,  =  141° 
48',  *4A*-J  =  118°    33V     Twins:    twinning-plane    i-l, 
common.     Also  massive. 

II.  —  6-6-5.  G.  =  7-S.  Lustre  nearly  pure  metallic, 
somewhat  adamantine.  Color  iron-black.  Streak  red- 
dish-brown to  black.  Opaque.  Brittle. 


/A  1  =101°  32', 


iT 


Comp.,  Var. — A  tantalate  either  (1)  of  iron,  or  (2)  of  iron  and 
manganese,  or  (3)  a  stanno-tantalate  of  these  two  bases.  Formula 
Fe(Mn)Ta2OG.  Sn  is  also  often  present  (as  FeSnO3.  according  to  Ram- 
melsberg', and  some  of  the  tantalum  is  often  replaced  by  columbium. 
Analysis,  Ramm.,  Tammela  (G.=7'384),  Ta2O5  7G'34,  Cb205  7'54, 
SnOa  0-TO.FeO  13-90,  MnO  1-42=99-90.  Other  varieties  contain  much 
more  Cb.^Oj,  the  kinds  shade  into  one  another. 

Pyr.,  etc.— B.B.  unaltered.  With  borax  slowly  dissolved,  yielding  an  iron  glass,  which,  at 
a  certain  point  of  saturation,  gives,  when  treated  in  R.F.  and  subsequently  flamed,  a  gray- 
ish-white bead ;  if  completely  saturated  becomes  of  itself  cloudy  on  cooling.  With  salt  of 
phosphorus  dissolves  slowly,  giving  an  iron  glass,  which  in  R.F.,  if  free  from  tungsten,  is 
pale  yellow  on  cooling  ;  treated  with  tin  on  charcoal  it  becomes  green.  If  tungsten  is  present 
the  bead  is  dark  red,  and  is  unchanged  in  color  when  treated  with  tin  on  charcoal.  With 
soda  and  nitre  gives  a  greenish-blue  manganese  reaction.  On  charcoal,  with  soda  and  suffi- 
cient borax  to  dissolve  the  iron,  gives  in  R.F.  metallic  tin.  Decomposed  on  fusion  with 

22 


338 


DESCRIPTIVE   MINERALOGY. 


potassium  bisulphate  in  the  platinum  spoon,  and  gives  on  treatment  with  dilute  hydrochloric 
acid  a  yellow  solution  and  a  heavy  white  powder,  which,  on  addition  of  metallic  zinc,  assumes 
a  smalt-blue  color  ;  on  dilution  with  water  the  blue  color  soon  disappears  (v.  Kobell). 

Obs. — Tantalite  is  confined  mostly  to  albite  or  oligoclase  granite,  and  is  usually  associated 
with  beryl.  Occurs  in  Finland,  at  several  places  ;  in  Sweden,  in  Fahlun,  at  Broddbo  and 
Finbo  ;  in  France,  at  Chanteloube  near  Limoges,  in  pegmatite  ;  in  North  Carolina. 

Named  Tantalite  by  Ekeberg,  from  the  mythic  Tantalus,  in  playful  allusion  to  the  difficul- 
ties (tantalizing)  he  encountered  in  his  attempts  to  make  a  solution  of  the  Finland  mineral  in 
acids. 

COLUMBITE.     Niobile.     Ferroilmenite. 

Orthorhombic.  I^  1=  101°  26',  O  A  14  =  134°  53^ ;  c:l\a  = 
1-0038  :  1-2225  :  1.  O  A  \-l  =  140°  36',  O  A  1-5  =  138°  26',  i-l  A  1-5  = 
104°  30',  1-4  A  1-8,  adj.,  =  151°,  i-&  A  i-&  ov.  i-l,  =  135°  40',  £2  A  £2,  ov.  i-l, 
=  135°  30'.  Twins  :  twinning-plane  2-£.  Cleavage :  i-l  and  i4,  the  former 
most  distinct.  Occurs  also  rarely  massive. 

661  662  663 


Haddam. 


Middletown,  Conn. 


Greenland. 


II.  =  6.  G.  =  5'4-6'5.  Lustre  submetallic ;  a  little  shining.  Color  iron- 
black,  brownish-black,  grayish-black ;  often  iridescent.  Streak  dark  red  to 
black.  Opaque.  Fracture  subconchoidal,  uneven.  Brittle. 

Comp.,  Var. — FeCb2(Ta2)06,  with  some  manganese  replacing  part  of  the  iron.  The  ratio 
of  Cb  :  Ta  generally =3  :  1  (Bodenmais,  Haddam),  sometimes  4  :  1,  8  :  1,  10  :  1,  etc.;  in  the 
Greenland  columbite  the  Ta2O5  is  almost  entirely  absent. 

Analyses,  Blomstrand,  (1)  Haddam  ^G.=615),  (2)  Greenland  (G.=5'395). 


(1) 
(2) 


Cb2O5 
51-53 

77-97 


Ta2O5 

28-55 


WC-3 
0-76 
0-13 


Sl302 

034 
0-73 


ZrO2 
0-34 
013 


FeO 
13-54 
17-33 


MnO 

4-97 
3-51 


H20 

0-16=100-19 

— =  99-80 


Pyr.3  etc. — Like  tantalite.  Von  Kobell  states  that  when  decomposed  by  fusion  with 
caustic  potash,  and  treated  with  hydrochloric  and  sulphuric  acids,  it  gives,  on  the  addition  of 
zinc,  a  blue  color  much  more  lasting  than  with  tantalite  ;  and  the  variety  dianite,  when 
similarly  treated,  gives,  on  boiling  with  tin-foil,  and  dilution  with  its  volume  of  water,  a 
sapphire-blue  fluid,  while,  with  tantalite  and  ordinary  columbite,  the  metallic  acid  remains 
undissolved.  The  variety  from  Ha.ddam,  Ct.,  is  partially  decomposed  when  the  powdered 
mineral  is  evaporated  to  dryness  with  concentrated  sulphuric  acid,  its  color  is  changed  to 
white,  light  gray,  or  yellow,  and  when  boiled  with  hydrochloric  acid  and  metallic  zinc  it  gives 
a  beautiful  blue.  The  remarkably  pure  and  unaltered  columbite  from  Arksut-fiord  in  Green- 
land is  also  partially  decomposed  by  sulphuric  acid,  and  the  product  gives  the  reaction  test 
with  zinc,  as  above. 

Obs. — Occurs  at  Rabenstein,  Bavaria ;  at  Tirschenreuth,  Bavaria ;  at  Tammela  in  Finland ; 
at  Chanteloube,  near  Limoges  ;  near  Miask  in  the  Ilmen  Mts.;  at  Hermanskar,  near  Bjorskar, 
in  Finland  ;  in  Greenland,  at  Evigtok. 


OXYGEN  COMPOUNDS. TANTALATES,  COLUMBATES. 


339 


In  the  United  States,  at  Haddam,  in  a  granite  vein,  and  near  Middletown,  Conn. ;  at 
Chesterfield,  Mass. ;  Standish,  Me.  ;  Acworth,  N.  H.  ;  also  Beverly,  Mass. ;  Northfield,  Mass.  ; 
Plymouth,  N.  H.  ;  Greenfield,  N.  Y. 

The  Connecticut  crystals  are  usually  rather  fragile  from  partial  change ;  while  those  of 
Greenland  and  of  Maine  are  very  firm  and  hard. 

HERMANNOLITE  (Shepard).  — From  the  columbite  locality  at  Haddam,  Ct.,  and  a  variety  of 
columbite  due  to  alteration.  G.  =5 '35.  Supposed  by  Hermann  to  contain  "ilmenium"  pent- 
oxide  (II,  O  5). 

TAPIOLITE.— Tetrngonal.  c=-6464  (rutile  c=-6442).  FeTa2(Cb2)06,  \vith  Ta  :  Cb=4  :  1. 
Tammela,  Finland. 

HJEL.MITE. — A  stanno-tantalate  of  iron,  uranium  and  yttrium.  Massive.  Color  black. 
Near  Fahlun,  Sweden. 


YTTROTANTALITE.     Black  Yttrotantalite. 

Orthorhombic.     I/\  1=  123°  10' ;  O  A  24  =  103°  26'; 
:  1-84:82  :  1.     Crystals   often   tabular   parallel   to  i-L 
Also  massive ;  amorphous. 

II.=5-5-5.      G.=5-4r-5-9. 
vitreous   and   greasy.     Color 


I :  &  =  2-0934: 


664 


Lustre   submetallic   to 
black,    brown.  •    Streak 


gray  to  colorless.     Opaque  to  subtranslucent. 
ture  small  conchoidal  to  granular. 


Frac- 


Comp.— Mostly  Jl2(Ta,Cb)2O7,  with  two  equivalents  of  water, 
perhaps  from  alteration  ;  R=Fe  :  Ca  :  Y(Er,Ce)  — 1  :  2  :  4.  Con- 
taining also  WO3  and  SnO2.  Analysis  (Ramm.),  Ytterby,  Ta2O6 
46-25,  Cb,05  12-82,  Sn02*M2,  WO3  2'36,  UO2  1-61,YO  10:52,  ErO 
6-71,  FeO  3-80,  CeO  2'22,  Ca  5-73,  H2O  6'31=98-95. 

Pyr.,  etc. — In  the  closed  tube  yields  water  and  turns  yellow. 


Ytterby. 


On  intense  ignition  becomes  white.  B.B.  infusible.  With  salt  of 
phosphorus  dissolves  with  at  first  a  separation  of  a  white  skeleton  of  tantalum  pentoxidts, 
which  with  a  strong  heat  is  also  dissolved  ;  the  black  variety  from  Ytterby  gives  a  glass  faintly 
tinted  rose-red  from  the  presence  of  tungsten.  With  soda  and  borax  on  charcoal  gives  traces 
of  metallic  tin  (Berzelius).  Not  decomposed  by  acids.  Decomposed  on  fusion  with  potas- 
sium bisulphate.  and  when  the  product  is  boiled  with  hydrychloric  acid,  metallic  zinc  gives  a 
pale  blue  color  to  the  solution  which  soon  fades. 

Obs. — Occurs  in  Sweden  at  Ytterby  ;  at  the  Kararfvet  mine,  etc.,  near  Fahlun. 


SAMARSKITE.     Uranotantalite. 


Orthorhombic.      /A  1=  122°  46'; 
1-833  :  1.      Crystals  often  flattened, 
parallel  to  *-£,  also  less  often  to  i-l. 
Also  in   large  irregular  masses  (N. 
Carolina).      In    flattened   imbedded 
grains  (Urals). 

II.  =  5-5-6.  G.=5-614-5-75 ;  5-45 
-5-69,  North  Carolina.  Lustre  of 
surface  of  fracture  shining  and  sub- 
metallic.  Color  velvet-black.  Streak 


dark  reddish-brown.  Opaque, 
ture  subconchoidal. 


Frac- 


Comp. — Analyses:     1.    Allen    (priv.    con- 
trib. ) ;  2.  Finkener  anfl  Stephana  : 


l-l  A  14  =  93°  :    c\l\&  —  0-949 


665 


North  Carolina. 


340  DESCRIPTIVE   MINERALOGY. 

Cb205  Ta2O5  W03  Sn02  Th02Zr02U03  MnO  FeO      CeO*      YO    CaO    H2O 

1.  Mitchell 

Co.,  N.  C.,  37-20  18.60  0-08 12-46  0'75  10-90    4'25    14'45  0'55  1-12= 

TJO2  100-36 

2.  Miask,  47'47    1'36  0'05  6'05  4-35  10-95  0 '96  ll-33f  3-31     12-61  0'73  0-45 

MgOO'14=99-76 

*  With  LaO,  DiO. 
+  With  0-J25  CuO. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  glows  like  gadolinite,  cracks  open,  and  turns 
black,  and  is  of  diminished  density.  B.B.  fuses  on  the  edges  to  a  black  glass.  With  borax 
in  O.F.  gives  a  yellowish-green  to  red  bead,  hi  R.F.  a  yellow  to  greenish -black,  which  on 
flaming  becomes  opaque  and  yellowish-brown.  With  salt  of  phosphorus  in  both  flames  an 
emerald-green  bead.  With  soda  yields  a  manganese  reaction.  Decomposed  on  fusion  with 
potassium  bisulphate,  yielding  a  yellow  mass  which  on  treatment  with  dilute  hydrochloric 
acid  separates  white  taiitalic  acid,  and  on  boiling  with  metallic  zinc  gives  a  fine  blue  color. 
Samarskite  in  powder  is  also  sufficiently  decomposed  on  boiling  with  concentrated  sulphuric 
acid  to  give  the  blue  reduction  test  when  the  acid  fluid  is  treated  with  metallic  zinc  or -tin. 

Obs. — Occurs  in  reddish-brown  feldspar,  near  Miask  in  the  Ural ;  the  pieces  having  the 
size  of  hazel-nuts.  In  masses,  sometimes  weighing  20  Ibs.,  in  the  decomposed  feldspar  of  the 
mica  mines  of  western  North  Carolina,  especially  in  Mitchell  Co.  At  both  localities  it  is 
often  intimately  associated  with  columbite  ;  at  Miask  the  crystals  of  the  latter  species  are 
sometimes  implanted  in  parallel  position  upon  those  of  the  samarskite. 

NOIILITE. — Near  samarskite,  but  contains  4 '62  p.  c.  water.     Nohl,  Sweden. 

EUXENITE. 

Orthorliombic.  Form  a  rectangular  prism  with  lateral  edges  replaced, 
and  a  pyramid  at  summit.  Cleavage  none.  Commonly  massive. 

H.  =  6*5.  G.=4r'60-4:'99.  Lustre  brilliant,  metallic-vitreous,  or  some- 
what greasy.  Color  brownish- black ;  in  thin  splinters  a  reddish-brown 
translucence  lighter  than  the  streak.  Streak-powder  yellowish  to  reddish- 
brown.  Fracture  subconchoidal. 

Comp. — According  to  Rammelsberg  2RTi03  +  RCb206  +  aq  ;  here  R=Y,Fe,TJ  mostly. 
Analysis,  Ramm.,  Arendal,  Cb2O5  35 '09,  TiOa  21 '16,  YO  27 '48,  ErO  3 '40,  UO2  4 '78,  CeO  3-17, 
FeO  1-38,  HaO  2-63=99-63. 

Obs.— Occurs  at  Jolster  in  Norway  ;  near  Tvedestrand  ;  at  Alve,  island  of  Tromoen,  near 
Arendal ;  at  Moretjar,  near  Naskilen.  North  Carolina. 

Named  by  Scheerer  from  €#|eyoy,  a  stranger,  in  allusion  to  the  rarity  of  its  occurrence. 

jiEsCHYNiTE. — Orthorhombic.  H.  —  5-6.  G.  =4 '9-5 '14.  Lustre  submetallic  to  resinous, 
nearly  dull.  Color  nearly  black.  Streak  gray.  Fracture  small  subconchoidal.  Analysis, 
Ramm.,  Cb2O5  28'81,  TiOa  22'64,  SnO2  018,  ThO2  15-75,  Fe03'17,  CeO  18 '49,  LaO(DiO) 
5-60,  YO  1-12,  CaO  2'75,  H2O  1-07=99-58.  In  feldspar  with  mica  and  zircon.  Miask  in  the 
Urals. 

POLYMIGNITE. — Orthorhombic.  In  slender  crystals.  H.=6'5.  G.=4'77-4-85.  Lustre 
brilliant.  Color  black.  Streak  dark  brown.  Fracture  perfect  conchoidal.  Composition 
doubtful.  Fredericksvarn,  Norway.  Perhaps  identical  with  asschynite  (Frankenheim). 

POLYCRASE. — Orthorhombic.  H.  =5'5.  G.  =5 '09-5-12.  Lustre  bright.  Color  black. 
Streak  grayish-brown.  Fracture  conchoidal.  Analysis,  Ramm.,  Cb^O5  20 '35,  Ta2O5  4'00, 
TiO2  26-59,  YO  23 '32,  FeO  2-72,  CeO  2'61,  UO2  7  '70  H20  4-02=98-84.  In  crystals  in  granite 
at  Hitteroe,  Norway. 

MENGITE. — Occurs  in  short  prisms.  H.=5-5-5.  G.=5'48.  Color  iron-black.  Contains 
zirconium,  iron,  titanium.  In  granite  veins  in  the  Ilmen  Mts. 

RUTIIERFORDITE. — Doubtf ul ;  contains  titanium,  cerium,  etc.     Rutherford  Co.,  N.  C. 


FERGUSONITE.    Yellow  Yttrotantalite.     Tyrite.     Bragite. 

Tetragonal,  hemihedral.     0  A  \4  =  124°  20' ;  c  =  1-464:.     Cleavage :  1, 
in  distinct  traces. 


OXYGEN  COMPOUNDS. TANTALATES,  COLUMBATES. 


341 


H.=5-5-6.     G.=5-838,  Allen;  5-800,  Turner.     Lustre  externally  dull, 
on  the  fracture  brilliantly  vitreous  and  subrnetallic. 
Color  brownish-black ;  in  thin  scales  pale  liver-brown. 
Streak  pale  brown.     8 nb translucent — opaque.     Frac- 
ture imperfect  conchoidal. 

Comp. — According  to  Rammelsberg,  essentially  2R3(Cb,Ta)2O8. 
Analysis,  Ramm.,  Greenland,  Cb2O5  44 '45.  Ta2O8  6 '30,  Sn02  0'47, 
WO3  0-15,  YO  24-87,  ErO  9  81,  Ce  7  "63  (5 '63  LaO,DiO),  UO2  2'58, 
FeO  0 '74,  CaO  0'61,  H.,O  1  -49 -.--99 10.  The  amount  of  water  varies 
from  1-49-7  p.  c.,  and  is  regarded  by  Rammelsberg  as  arising  from 
alteration. 

Obsr — Fergusonite  occurs  near  Cape  Farewell  in  Greenland,  dis- 
seminated in  quartz.  Also  found  at  Ytterby,  Sweden  ;  in  Silesia. 
Bragite  is  from  Helle,  Alve,  and  elsewhere  in  Norway.  Tyrite  is 
associated  with  euxenite  at  Hampemyr  on  the  island  of  Tromoe, 
and  Helle  on  the  mainland ;  at  Naeskul,  about  ten  miles  east  of 
Arendal. 

KOCIIELITE. — Near  fergusonite.      In  yellow  square -octahedrons  and  crusts  in  granite. 
Kochelwiesen,  near  Schreiberhau,  Silesia. 

ADELPHOLITE. — A  columbate  of  iron  and  manganese,  containing  41 '8  p.  c.  of  metallic 
acids,  and  9'7  p.  c.  of  water.     Tetragonal.     H.=3'5-4'5.     G-.=3'8.     Tammela,  Finland. 


342 


DESCRIPTIVE   MINERALOGY. 


3.  PHOSPHATES,  AKSENATES,  VAKADATES,  ETC. 


ANHYDROUS  PHOSPHATES,  ARSENATES,  ETC. 
XENOTIME.    Ytterspath,   Germ. 

Tetragonal.     0  A  1  =  138°  45' ;  c  =  0-6201.     1  A  1,  pyram.,  =  124°  26' ; 

basal,  =  82°  30'.     Cleavage :  7,  perfect. 

668  H.=4-5.       G.  =4-45-4-56.       Lustre    resinous. 

Color  yellowish-brown,  reddish-brown,  hair-brown, 
flesh-red,  grayish-white,  pale  yellow ;  streak  pale 
brown,  yellowish,  or  reddish.  Opaque.  Fracture 
uneven  and  splintery. 


Comp. — Y»PaOt=Phpsphorufl  pentoxide  (P205)  37 '87,  yttria 
62-13=100. 

Pyr.,  etc — B.B.  infusible.     When  moistened  with  sulphuric 
acid  colors  the  flame  bluish-green.     Difficultly  soluble  in  salt 
of  phosphorus.     Insoluble  in  acids. 
Obs.— From  a  granite  vein  at  Hitteroe  ;  at  Ytterby,  Sweden  ;  St.  Gothard  ;  Binnenthal. 
In  the  U.  S.,  in  the  gold  washings  of  Clarksville,  Georgia  ;  in  McDowell  Co.,  N.  C.;  in  the 
diamond  sands  of  Bahia,  Brazil.     The  wiaerine  of  Kenugott  has  been  shown  by  Klein  to  be 
octahedrite  (vide  p.  255). 

CBYPTOLITE  (PJiospfiocerite) . — Ce3P208  (with  some  Di),  like  monazite.     Occurs  in  minute 
grains  imbedded  in  apatite  at  Arendal ;  Siberia. 


Apatite  Group. 

APATITE. 

Hexagonal ;  often  hemihedral.     0  A  1  =  139°  41'  38",  Kokscharof  ;  c  = 
0-734603.    O  A  2-2  =•  124°  14J'.    Cleavage :  0,  imperfect ;  /,  more  so.    Also 


St.  Gothard. 


globular  and  reniform,  with  a  fibrous  or  imperfectly  columnar  structure  ; 
also  massive,  structure  granular. 


OXYGEN    COMPOUNDS. — PHOSPHATES,   AESENATES,    ETC.  343 

H.  —  5,  sometimes  4-5  when  massive.  G.=2'92-3'25.  Lustre  vitreous, 
inclining  to  subresinous.  Streak  white.  Color  usually  sea-green,  bluish- 
green  ;  often  violet-blue ;  sometimes  white ;  occasionally  yellow,  gray,  red, 
flesh-red,  and  brown  ;  none  bright.  Transparent — opaque.  A  bluish 
opalescence  sometimes  in  the  direction  of  the  vertical  axis,  especially  in 
white  varieties.  Cross  fracture  conchoidal  and  uneven.  Brittle. 

Var. — 1.  Ordinary.  Crystallized,  or  cleavable  and  granular  massive,  (a}  The  asparagus 
stone  (originally  from  Murcia,  Spain)  and  moroxite  (from  Arendal)  are  ordinary  apatite.  The 
former  was  yellowish-green,  as  the  name  implies  ;  the  latter  was  in  greenish-blue  and  bluish 
crystals  ;  and  the  names  have  been  used  for  apatite  of  the  same  shades  from  other  places. 
2.  Fibrous,  concretionary,  stalactitic.  The  name  PJw^phorite  was  used  by  Kirwan  for  all  apatite, 
but  in  his  mind  it  especially  included  the  fibrous  concretionary  and  partly  scaly  mineral  from 
Estremadura,  Spain,  and  elsewhere.  3.  Fluor -apatite,  Chlor -apatite.  Apatite  also  varies  as 
to  the  proportion  of  fluorine  to  chlorine,  one  of  these  elements  sometimes  replacing  nearly  or 
wholly  the  other. 

Comp.— The  formulas  of  the  two  varieties  are  3Ca3P2O8-t-  CaClQ= Phosphorus  pentoxide 
40-92,  lime  53-80,  chlorine  6 -82= 101 '54  ;  and3Ca3P2O8  +  CaF2=Phosphoruspentoxide  42'2(>, 
lime  55 '55,  fluorine  3'77= 101 '58.  Sometimes  both  calcium  chloride  (CaCl2),  and  calcium 
fluoride  (CaF2),  are  present. 

Pyr.  etc. — B.B.  in  the  forceps  fuses  with  difficulty  on  the  edges  (F.=4'5-5),  coloring  the 
flame  reddish-yellow  ;  moistened  with  sulphuric  acid  and  heated  colors  the  flame  pale  bluish- 
green  (phosphoric  acid) ;  some  varieties  react  for  chlorine  with  salt  of  phosphorus,  when  the 
bead  has  been  previously  saturated  with  copper  oxide,  while  others  give  fluorine  when  fused 
with  this  salt  in  an  open  glass  tube.  Gives  a  phosphide  with  the  sodium  test. 

Dissolves  in  hydrochloric  and  nitric  acid,  yielding  with  sulphuric  acid  a  copious  precipitate 
of  calcium  sulphate  ;  the  dilute  nitric  acid  solution  gives  with  lead  acetate  a  white  precipi- 
tate, which  B.  B.  on  charcoal  fuses,  giving  a  globule  with  crystalline  facets  on  cooling.  Some 
varieties  of  apatite  phosphoresce  on  heating. 

Diff. — Characterized  by  its  hexagonal  form.  Distinguished  by  its  softness*  -from  beryl ; 
does  not  effervesce  with  acids  like  the  carbonates  ;  unlike  pyromorphite,  yields  no  lead  B.B. 

Obs, — Apatite  occurs  in  rocks  of  various  kinds  and  ages,  but  is  most  common  in  metamor- 
phic  crystalline  rocks,  especially  in  granular  limestone,  granitic  and  many  metalliferous  veins, 
particularly  those  of  tin,  in  gneiss,  syenite,  hornblendic  gneiss,  mica  schist,  beds  of  iron  ore ; 
occasionally  in  serpentine,  and  in  igneous  or  volcanic  rocks  ;  sometimes  in  ordinary  stratified 
limestone,  beds  of  sandstone  or  shale  of  the  Silurian,  Carboniferous,  Jurassic,  Cretaceous,  or 
Tertiary  formations  ;  also  in  microscopic  crystals  in  many  igneous  rocks,  doleryte,  etc.  It 
has  been  observed  as  the  petrifying  material  of  wood. 

Among  its  prominent  localities  are  Ehrent'riedersdorf  in  Saxony ;  region  of  St.  Gothard 
in  Switzerland ;  Mussa-Alp  in  Piedmont ;  Untersulzbachthal  and  elsewhere  in  the  Tyrol ; 
Bohemia  ;  in  England,  in  Cornwall,  with  tin  ores  ;  in  Cumberland  ;  in  Devonshire  ;  at  Wheat 
Franco  (francolite),  etc.  The  variety,  moroxite,  occurs  at  Arendal,  Snarum,  etc.,  in  Norway. 
The  asparagus  stone  or  Spargelstein  of  Jumilla,  in  Murcia,  Spain,  is  pale  yellowish-green  in 
color ;  and  a  variety  from  Zillerthal  is  wine-yellow.  The  phosphorite,  or  massive  radiated 
variety,  is  obtained  abundantly  near  the  junction  of  granite  and  argillyte,  in  Estremadura, 
Spain  ;  at  Schlackenwald  in  Bohemia ;  at  Krageroe,  etc. 

In  Mass.,  at  Norwich;  at  Bolton,  and  elsewhere.  In  New  York,  in  St.  Lawrence  Co.,  in 
granular  limestone;  in  Rossie;  Sanford  mine,  Essex  Co.;  near  Edenville,  Orange  Co.  In 
New  Jersey,  near  Suckasunny,  ;  Mt.  Pleasant  mine,  near  Mt.  Teabo  ;  at  Hurdstown,  Sussex 
Co.  In  Penn.,  at  Leiperville,  Delaware'Co.;  in  Chester  Co.  In  Delaware,  at  Dixon's  quarry, 
Wilmington.  In  Canada,  in  North  Elmsley,  and  passing  into  South  Burgess  ;  similar  in 
Boss  ;  at  the  foot  of  Calumet  Falls ;  at  St.  Roch,  on  the  Achigan. 

Apatite  was  named  by  Werner  from  airardu),  to  deceive,  older  mineralogists  having  referred 
it  to  aquamarine,  chrysolite,  amethyst,  fluor,  schorl,  etc. 

OSTEOLITE  is  massive  impure  altered  apatite.  The  ordinary  compact  variety  looks  like 
lithographic  stone  of  white  to  gray  color.  It  also  occurs  earthy.  Hanau. 

GUANO. — Guano  is  bone-phosphate  of  calcium,  or  osteolite,  mixed  with  the  hydrous  phos- 
phate, brushite,  and  generally  with  some  carbonate  of  calcium,  and  often  a  little  magnesia, 
alumina,  iron,  silica,  gypsum,  and  other  impurities.  It  often  contains  9  or  10  p.  c.  of  water. 
It  is  often  granular  or  oolitic  ;  also  compact  through  consolidation  produced  by  infiltrating 
waters,  in  which  case  it  is  frequently  lamellar  in  structure,  and  also  occasionally  stal  -gmitic 
and  stalactitic.  Its  colors  are  usually  grayish-white,  yellowish  and  dark  brown,  and  some- 
times reddish,  and  the  lustre  of  a  surface  of  fracture  earthy  to  resinous. 


344 


DESCRIPTIVE   MINERALOGY. 


PHOSPHATIC  NODULES.  COPROLITES.—  Phosphatic  nodules  occur  in  many  fossiliferous 
rocks,  which  are  probably  in  all  cases  of  organic  origin.  They  sometimes  present  a  spiral  or 
other  interior  structure,  derived  from  the  animal  organization  that  afforded  them,  and  in 
such  cases  their  coprolitic  origin  is  unquestionable.  In  other  cases  there  is  no  structure  to  aid 
in  deciding  whether  they  are  true  coprolites  or  not. 

PYROMORPHITE     Griinbleierz,  Germ. 

Hexagonal.  Hemihedral.  O  A  1  =  139°  38'  ;  c  =  07362.  Cleavage  : 
1  and  1  in  traces.  /  commonly  striated  horizontally.  Often  globular, 
reniform,  and  botryoidal  or  verruciform,  with  usually  a  subcolumnar  struc- 
ture ;  also  fibrous,  and  granular. 

H.=3*5-4.  G.  =  6'5-7'l,  mostly  when  without  lime;  5-6'5,  when  con- 
taining lime.  Lustre  resinous.  Color  green,  yellow,  and  brown,  of  differ- 
ent shades  ;  sometimes  wax-yellow  and  fine  orange-yellow  ;  also  grayish- 
white  to  milk-white.  Streak  white,  sometimes  yellowish.  Subtrausparent 
—  subtranslucent.  Fracture  subconchoidal,  uneven.  Brittle. 

Comp  —  Analogous  to  apatite,  3Pb3P2O8+PbCl2=Phosphorus  pentoxide  15  '71,  lead  oxide 
82  '27,  chlorine  2-02  =  100  '60.  Some  varieties  contain  arsenic  replacing  part  of  the  phosphorus, 
and  others  calcium  replacing  the  lead. 

Fyr.!  etc.  —  In  the  closed  tube  gives  a  white  sublimate  of  lead  chloride.  B.B.  in  the  forceps 
fuses  easily  (F.=1'5),  coloring  the  flame  bluish-green  ;  on  charcoal  fuses  without  reduction 
to  a  globule,  which  on  cooling  assumes  a  crystalline  polyhedral  form,  while  the  coal  is  coated 
white  from  the  chloride,  and,  nearer  the  assay,  yellow  from  lead  oxide.  With  soda  on  charcoal 
yields  metallic  lead  ;  some  varieties  contain  arsenic,  and  give  the  odor  of  garlic  in  R.F.  on 
charcoal.  With  salt  of  phosphorus,  previously  saturated  with  copper  oxide,  gives  an  azure- 
blue  color  to  the  flame  when  treated  in  O.F.  (chlorine).  Soluble  in  nitric  acid. 

Diff.  —  Characterized  by  its  high  specific  gravity,  and  pyrognostics. 

Obs.  —  Pyromorphite  occurs  principally  in  veins,  and  accompanies  other  ores  of  lead.  Occurs 
in  Saxony  ;  at  Przibram,  Mies,  and  Bieistadt,  in  Bohemia;  near  Freiberg  ;  Clausthal  in  the 
Harz  ;  at  Nassau  ;  Beresof  in  Siberia  ;  Cornwall,  Derbyshire,  and  Cumberland,  in  England  ; 
Leadhills  in  Scotland  ;  Wicklow,  and  elsewhere,  Ireland.  In  the  U.  S.  at  Phenixville,  Penn.; 
also  in  Maine,  at  Lubec  and  Lenox  ;  in  Davidson  Co.  ,  N.  C. 

The  figures  produced  by  etching  (see  p.  118)  show  that  pyromorphite  is  heniihedral  like 
apatite  (Baumhauer). 

Named  from  irup,  fire,  M-opQ-f),  form,  alluding  to  the  crystalline  form  the  globule  assumes  on 
cooling. 


MIMETITE.     Mimetesite. 

Hexagonal.     #Al=:1390   58';  c  =  0-7276.      Cleavage:  1,  imperfect. 
H.=3'5.      G.=7'0-7-25,   mimetite  ;    5-4-5-5,   hedy- 
phane.     Lustre  resinous.     Color  pale  yellow,   passing 
into  brown;  orange-yellow;  white  or  colorless.    Streak 
white  or  nearly  so.     Subtransparent  —  translucent. 

Comp.  —  Formula  3Pb3As2O8+PbCl2  =  Arsenic  pentoxide  23-20, 
lead  oxide  74-96,  chlorine  2-39=100'55.  Generally  part  of  the 
arsenic  is  replaced  by  phosphorus,  and  often  the  lead  in  part  by  cal- 
cium. 

Fyr.  etc.—  In  the  closed  tube  like  pyromorphite.  B.B.  fuses  at  1, 
and  on  charcoal  gives  in  R.F.  an  arsenical  odor,  and  is  easily  reduced 
to  metallic  lead,  coating  the  coal  at  first  with  lead  chloride,  and 
later  with  arsenous  oxide  and  lead  oxide.  Gives  the  chlorine  reac- 
tions as  under  pyromorphite.  Soluble  in  nitric  acid. 

Obs.  —  Occurs  at  several  of  the  mines  in  Cornwall  ;  in  Cumberland.     At  St.  Prix  in  France  ; 
at  Johanngeorgenstadt  ;  at  Nertschinsk,  Siberia.     At  the  Brookdale  mine,  Phenixville,  Pa. 


OXYGEN    COMPOUNDS. PHOSPHATES,    ARSENATES,    ETC.  345 

Mimetite  is  hemihedral  like  apatite  and  pyromorphite,  as  shown  by  etching  (Baumhauer). 
Named  from  ^TJT^S,  imitator,  it  closely  resembling  pyromorphite. 

HEDYPIIANE.— A  variety  containing  much  calcium.     CAMPYLITE  contains  much  lead  phos- 
phate. 


VANADINITE. 

Hexagonal.  In  simple  hexagonal  prisms,  and  prisms  terminating  in 
planes  of  the  pyramids  ;  1  A  1,  over  terminal  edge,  142°  58',  O  A  1  =  140° 
34',  /A  1  =  130°.  Usually  in  implanted  globules  or  incrustations. 

II.  =  2'75-3.  G.= 6-6623-7. 23.  Lustre  of  surface  of  fracture  resinous. 
Color  light  brownish-yellow,  straw-yellow,  reddish-brown.  Streak  white  or 
yellowish.  Subtranslucent — opaque.  Fracture  uneven,  or  fiat  corichoidal. 
Brittle. 

Comp,— Formula  3Pb3V208+PbCl2  = Vanadium  pentoxide  19 '36,  lead  oxide  78 '70  chlorine 
2  -50 =100  "56. 

Pyr.,  etc. — In  the  closed  tube  decrepitates  and  yields  a  faint  white  sublimate.  B.B.  fuses 
easily,  and  on  charcoal  to  a  black  lustrous  mass,  which  in  R.  F.  yields  metallic  lead  and  a  coat- 
ing of  chloride  of  lead  ;  after  completely  oxidizing  the  lead  in  O.F  the  black  residue  gives 
with  salt  of  phosphorus  an  emerald-green  bead  in  R.F.,  which  becomes  light  yellow  in  O.F. 
Gives  the  chlorine  reaction  with  the  copper  test.  Decomposed  by  hydrochloric  acid. 

If  nitric  acid  be  dropped  on  the  crystals  they  become  first  deep  red  from  the  separation  of 
vanadium  pentoxide,  and  then  yellow  upon  its  solution. 

Obs. — This  mineral  was  first  discovered  at  Zimapan  in  Mexico,  by  Del  Rio.  Since  obtained 
at  Wanlockhead  in  Dumfriesshire  ;  also  at  Beresof  in  the  Ural ;  and  near  Kappel  in  Carinthia. 


DECHENITE.—  PbV206  (or  with  some  Zn}=  Vanadium  pentoxide  451,  lead  oxide  54-9=100. 
Massive.  Color  deep  red.  Dahn,  near  Niederschlettenbach,  Rhenish  Bavaria.  Freiberg  in 
Breisgau  (eusyncMte). 

DESCLOIZITE. — Pb2V207=Vanad  um  pentoxide  291,  lead  oxide  70'9  =  100.  Orthorhombic. 
South  America.  Wheatley  Mine,  Penn. 

PUCIIERITE  (Frenzel). — Orthorhombic,  near  brookite  in  form  (Websky).  Occurs  in  small 
implanted  crystals.  Color  reddish-brown.  In  composition  a  bismuth  vanadate,  BiY04  = 
Vanadium  pentoxide  28-3.  bismuth  oxide  71 '7.  Pucher  mine,  Schneeberg,  Saxony. 


ROSCOELITE. — Occurs  in  thin  micaceous  scales,  arranged  in  stellate  or  fan-shaped  groups. 
Color  dark  brownish-green.  Soft.  G.=2'938  (Genth) ;  2*902  (Roscoe).  Analyses:  1.  Ros- 
coe  (Proc.  Roy.  Soc.,  May  10,  1876);  2.  Genth  (Am.  J.  Sci.,  July,  1876). 

SiO2       V2O5  iV!O3      FeO3  MnO3     MgO      CaO       KoO     Na2O       H  O 

1.  |41-25      28-60  14-14      113  115      2'01      0'61      8'56      0'82       1'08 

mpisture  2 '27=101 '62 

2.  47-69      23-02  V60n      1410      1'67  FeO        2'00        tr.       V59      019ign.4'96 

0-85  gangue=100-22 

The  above  analyses,  made  upon  material  derived  from  the  same  source,  differ  widely, 
especially  in  regard  to  the  state  of  oxidation  of  the  vanadium.  Genth  makes  it  V6Oii  = 
2  V203,V.2OS.  The  formula  given  by  Roscoe  is  2MV2O8  +  K4Si9O20  -f-  aq.  Found  in  fissures  in 
the  porphyry,  and  in  cavities  in  quartz  at  the  gold  mine  at  Granite  Creek,  El  Dorado  Co., 
Cal.  Named  by  Dr.  Blake,  who  discovered  it. 


346 


DESCRIPTIVE   MINERALOGY. 


WAGNERITB. 


,  /A  7=  95°  25',  0  A  14  =  144°  25',  B.  &  M. ; 


Monoclinic.     (7  =  71°  53  , 

c  :  b  :  d  =  0-78654  :  1-045  :  1.    Most  of  the  prismatic  planes  deeply  striated. 
Cleavage  :  7,  and  the  orthodiagonal,  imperfect ;   O  in  traces. 

H.=5-5'5.  G.= 3-068,  transparent  crystal;  2'985,  untransparent,  Ram- 
inelsberg.  Lustre  vitreous.  Streak  white.  Color  yellow,  of  different 
shades  ;  often  grayish.  Translucent.  Fracture  uneven  and  splintery  across 
the  prism. 

Comp. — Mg3P208+MgF2=:  Phosphorus  pentoxide  43 '8,  magnesia  37*1,  fluorine  11 '7  mag- 
nesium 7-4=100. 

Pyr.,  etc.— B.B.  in  the  forceps  fuses  at  4  to  a  greenish-gray  glass  ;  moistened  with  sulphu- 
ric acid  colors  the  flame  bluish-green.  With  borax  reacts  for  iron.  On  fusion  with  soda 
effervesces,  but  is  not  completely  dissolved  ;  gives  a  faint  manganese  reaction.  Fused  with 
salt  of  phosphorus  in  an  open  glass  tube  reacts  for  fluorine.  Soluble  in  nitric  and  hydro- 
chloric acids.  With  sulphuric  acid  evolves  fumes  of  fluohydric  acid. 

Obs. — Occurs  in  the  valley  of  Hollgraben,  near  Werfen,  in  Salzburg,  Austria. 

KJERULFINE  (v.  Kobett). — Stands  near  wagnerite,  but  exact  nature  uncertain.  In  masses 
of  a  pale  red  color  at  Bamle,  Norway. 


MONAZITE. 


672 


Monoclinic.      C  =  76°  14',  /A  7  =  93°  10',    O  A  14  =  138°  8';  c  :  I  :  a 

=  0-94715  :  1-0265  :  1.  Crys- 
tals usually  flattened  parallel*  to 
i-i.  Cleavage  :  O  very  perfect, 
and  brilliant.  Twins:  twin- 
ning plane  O. 

H.  =  5-5-5.  G.  =  4-9-5-26. 
Lustre  inclining  to  resinous. 
Color  brownish-hyacinth-red, 
clove-brown,  or  yellowish- 
brown.  Subtransparent — sub- 
translucent.  Rather  brittle. 


Norwich,  Ct. 


-it 
Watertown,  Ct. 


Comp.  —  According  to  Rammelsberg, 
5R3P208+Th2P2O9,  where  R=Ca,La, 
Di.      Analysis   by    Kersten,    Slatoust, 
P205  28-50,  ThO2  17-95,  Sn02  210,  CeO  26  -00,  LaO  23'40,  MnO  1'86,  CaO  1-68,  K-0  and  TiO, 


Pyr.,  etc.  —  B.B.  infusible,  turns  gray,  and  when  moistened  with  sulphuric  acid  colors  the 
flame  bluish-green.  With  borax  gives  a  bead  yellow  while  hot  and  colorless  on  cooling  ;  a 
saturated  bead  becomes  enamel-  white  on  flaming.  Difficultly  soluble  in  hydrochloric  acid. 

Diff.  —  Its  brilliant  basal  cleavage  is  a  prominent  character,  distinguishing  it  from  tita- 
nite. 

Obs.—  Monazite  occurs  near  Slatoust  in  the  Ilmen  Mtn.  ;  also  in  the  Ural  ;  near  Notero  in 
Norway  ;  at  Schreiberhau.  In  the  United  States,  with  sillimanite  at  Norwich  ;  at  Yorktown, 
Westchester  Co.,  N.Y.  ;  near  Crowder's  Mountain,  N.  C. 

Named  from  //oraCw,  to  be  solitary,  in  allusion  to  its  rare  occurrence. 

TURNERITE.  —  Identical  with  monazite,  as  first  suggested  by  Prof.  J.  D.  Dana.  Occurs  in 
minute  yellow  to  brown  crystals,  rarely  twins,  at  Mt.  Sorel,  Dauphiny  ;  Santa  Brigritta, 
Tavetsch;  Lercheltiny  Alp,  Binnenthal  ;  Laacher  See  (v.  Rath.),  c  :  b  :  a='921G96  :  1  : 
0-958444.  (7.  =77°  IS'  (Trechmann). 

KORARFVEITE  (  Radomimki)  .  —  A  cerium  phosphate  containing  fluorine  ;  near  monazite. 
Occurs  in  large  crystalline  masses  of  a  yellowish  color  at  Korarfet  near  Fahlun,  Sweden. 


OXYGEN    COMPOUNDS. PHOSPHATES,    ARSENATES,   ETC.  347 


TRIPHYLITE.     Triphyline. 

Orthorhombic.     /A  7=  98°,  O  A 14  =  129°  33',  Tschermak ;  c  :  I 
1-211  :  1-1504  :  1.      Faces   of   crystals   usually   uneven. 
Cleavage  :     O    nearly    perfect    in    unaltered    crystals.  674 

Massive.  s?     To 

H.=5.  G.= 3-54-3-6.  Subresinous.  Color  greenish- 
gray  ;  also  bluish  ;  often  brownish-black  externally. 
Streak  grayish-white.  Translucent  in  thin  fragments. 


il 


Comp.— R3P2O8,  where  R=Fe,  Mn,  (Ca)  and  Li2  (Ka,  Na2).  Analysis 
by  Oesten,  from  Bodenraais,  P2O6  44'19,  FeO  38'21,  MnO  5 '63,  MgO 
2-39,  CaO  0-76,  Li2O  7 -69,  Na2O  0*74,  K20  0'04,  Si02  0-40=100-05. 
The  analyses  vary  much,  owing  to  the  impure  material  employed. 

Pyr,,  etc. — In  the  closed  tube  sometimes  decrepitates,  turns  to  a  Norwich, 

dark  color,  and  gives  off  traces  of  water.     B.B.  fuses  at  1*5,  coloring 

the  flame  beautiful  lithia-red  in  streaks,  with  a  pale  bluish-green  on  the  exterior  of  the  cone 
of  flame.  The  coloration  of  the  flame  is  best  seen  when  the  pulverized  mineral,  moistened 
with  sulphuric  acid,  is  treated  on  a  loop  of  platinum  wire.  With  borax  gives  an  iron  bead  ; 
with  soda  a  reaction  for  manganese.  Soluble  in  hydrochloric  acid. 

Obs. — Triphylite  occurs  at  Rabenstein  near  Zwiesel  in  Bavaria  ;  also  at  Keityo  in  Finland ; 
Norwich,  Mass. 

Named  from  rptg ,  three-fold,  and  ^v^,  family,  in  allusion  to  its  containing  three  phos- 
phates. 

TRIPLITE.     Zwieselite. 

Orthorhombic.  Imperfectly  crystalline.  Cleavage:  unequal  in  three 
directions  perpendicular  to  each  other,  one  much  the  most  distinct. 

Ii.i=5-5-5.  G.  =  3-44-3-8.  Lustre  resinous,  inclining  to  adamantine. 
Color  brown  or  blackish-brown  to  almost  black.  Streak  yellowish- gray  or 
brown.  Sub  translucent — opaque.  Fracture  small  conchoidal. 

Comp.— R3PoOa+RF2 ;  R=Fe,  Mn(Ca).  Analysis,  v.  Kobell,  Schlackenwald,  P205  33*85, 
FeO3  3-50,  FeO  23 -38,  MnO  30'00,  CaO  2'20,  MgO  3 "05,  F=8-10=104-08. 

Pyr.,  etc. — B.B.  fuses  easily  at  1'5  to  a  black  magnetic  globule;  moistened  with  sulphuric 
acid  colors  the  flame  bluish-green.  With  borax  in  O.F.  gives  an  amethystine  colored  glass 
(manganese);  in  R.F.  a  strong  reaction  for  iron.  With  soda  reacts  for  manganese.  With 
sulphuric  acid  evolves  fluohydric  acid.  Soluble  in  hydrochloric  acid. 

Obs. — Found  by  Alluaud  at  Limoges  in  France,  with  apatite ;  at  Peilau  in  Silesia. 

Zwieselite,  a  clove-brown  variety,  was  found  near  Rabenstein,  near  Zwiesel  in  Bavaria,  in 
quartz  (Gk=3'97,  Fuchs). 

SAKCOPSIDE. — Near  triplite.     Valley  of  the  Miihlbach,  Silesia. 

AMBLYGONITB. 

Triclinic.  Cleavage :  O  perfect ;  i-1  nearly  perfect,  angle  between  these 
cleavages  104J°  ;  also  /imperfect.  Usually  massive,  cleavable ;  sometimes 
columnar. 

IL=6.  Gr.=3-34ll.  Lustre  pearly  on  face  of  perfect  cleavage  (O); 
vitreous  on  i-i,  less  perfect  cleavage-face  ;  on  cross-fracture  a  little  greasy. 
Color  pale  mountain  or  sea-green,  white,  grayish,  brownish- white.  Sub- 
transparent — translucent.  Fracture  uneven.  Optical  axes  very  divergent ; 
plane  of  axes  nearly  at  right  angles  to  i-l ;  bisectrix  of  the  acute  angle 
negative,  and  parallel  to  the  edge  0/i-i',  DesCl. 


34:8 


DESCRIPTIVE   MINERALOGY. 


Comp. — According  to  Rammelsberg,  2AlP.208-f  3Li(Na)F.     If  Na  :  Li=l  :  4,  the  formula 
requires  :   Phosphorus  pentoxide  49'24,  alumina  35*58,  lithia  6 '24,  soda 
675  3-23,  fluorine  9 -88=104-17. 

Pyr.,  etc. — In  the  closed  tube  yields  water,  which  at  a  high  heat  is 
acid  and  corrodes  the  glass.  B.  B.  fuses  easily  at  2,  with  intumescence, 
and  becomes  opaque-white  on  cooling.  Colors  the  flame  yellowish- red 
with  traces  of  green ;  the  Hebron  variety  gives  an  intense  lithia-red  ; 
moistened  with  sulphuric  acid  gives  a  bluish-green  to  the  flame.  With 
cobalt  solution  assumes  a  deep  blue  color  (alumina).  With  borax  and 
salt  of  phosphorus  forms  a  transparent  colorless  glass.  In  fine  powder 
dissolves  easily  in  sulphuric  acid,  more  slowly  in  hydrochloric. 

Diff. — Distinguished  by  its  easy  fusibility  ;  reaction  for  fluorine  and 
lithia ;  greasy  lustre  in  the  mass,  etc. 

Obs. — Occurs  at  Chursdorf  and  Arnsdorf ,  near  Penig  in  Saxony ;  also 
at  Arendal,  Norway.  In  the  U.  States,  in  Maine,  at  Hebron  (hebronite), 
imbedded  in  a  coarse  granite  with  lepidolite,  albite,  quartz,  red,  green, 
and  black  tourmaline ;  also  at  Mt.  Mica  in  Paris,  8m.  from  Hebron, 
with  tourmaline. 

The  name  is  from  opy3A6f,  Hunt,  and  ydw,  angle. 
HKBHONITE. — The  mineral  from  Hebron,  Me.  (see  above),  has  been 
shown  by  DesCloizeaux  to  differ  in  optical  character  (v  >  /;)  from  the 
Penig  amblygonite.  On  this  ground,  as  well  as  on  account  of  a  variation 
in  the  composition,  it  has  been  proposed  (v.  Kobell)  to  make  it  a  new  species.  The  same 
optical  character  and  composition  belong  to  the  mineral  from  Montebras  (called  montebrasite 
on  the  basis  of  an  erroneous  analysis).  Analysis  of  hebronite,  Pisani,  P^Os  46'65,  A1O3 
3G-00,  Li.O  9-75,  H2O  4 -20,  F  5-22=101-82. 

HERDERITE. — Supposed  to  be  an  anhydrous  aluminum-calcium  phosphate,  with  fluorine. 
Color  yellowish- white.  Ehrenfriedersdorf. 

PURANGITE.— Monoclinic.  Cleavage  prismatic  (110°  10').  H.=5.  G.=3'937-4-07.  Color 
bright  orange-red.  Analysis,  Hawes,  Arsenic  pentoxide  53'11,  alumina  17'19,  iron  sesqui- 
oxide  9'23,  manganese  sesquioxide  2 '08,  soda  13'0(>,  lithia  0'65,  fluorine  7 '67=102-99. 


Hebronite,  Maine. 


Formula  E,2RAs2O9  (with  one -ninth  of  the  oxygen  replaced  by  fluorine),  or  RAs20 

Here  R=Na  :  Li=10  :  1 ;  ft=A-l  :  Fe  :  Mn=15  :  5  :  1.  Other  varieties,  having  a  lighter  color, 

have  Al  :  Fe— 5  :  1.     Occurs  with  cassiterite,  near  Durango,  Mexico  (Brush). 


ANHYDROUS  ANTIMONATES. 


MONIMOLITE. — Mainly  an  an timon ate  of  lead.     Yellow.     G.=5"94.     Paisberg,  Sweden. 

NADOKITE.— PbSb,O4  +  PbCl2.  In  yellow  translucent  crystals.  H.  =3.  G.  =7  -02.  Djebel- 
Nador,  province  of  Constantine,  Algiers. 

ROMEITE.  — An  antimonate  (or  antimonite)  of  calcium.  Occurs  in  groups  of  minute  tetra- 
gonal crystals.  Color  yellow.  St.  Marcel,  Piedmont. 

RIVOTITE. — Contains  antimonic  oxide,  carbon  dioxide,  and  copper.  Amorphous.  Color 
yellowish-green.  Sierra  del  Cadi. 

STIBIOFERKITE. — Amorphous  coating  on  stibnite,  from  Santa  Clara  Co.,  Cal.    Mixture  (?). 


HYDROUS  PHOSPHATES,  ARSENATES,  ETC. 

PHARMACOLITE. 

Monoclinic.  /A  7=  111°  6',  i4  A  i-2  =  109°  26',  1  A  1  =  117°  24'. 
Cleavage :  i-l  eminent.  One  of  the  faces  1  often  obliterated  by  the  exten- 
sion of  the  other.  Surfaces  i-i  and  *-2  usually  striated  parallel  to  their 
mutual  intersection.  Barely  in  crystals ;  commonly  in  delicate  silky  fibres 
or  acicular  crystallizations,  in  stellated  groups.  Also  botryoidal  and  stalac- 
titic,  and  sometimes  massive. 


OXYGEN   COMPOUNDS. — PHOSPHATES,    AESENATE3,    ETC. 


349 


H.— 2-2*5.     G.= 2-64^2 -73.     Lustre  vitreous  ;  on  i-l  inclining  to  pearly. 
Color  white  or  grayish  ;  frequently  tinged  red 
by  arsenate   of   cobalt.     Streak  white.     Trans- 
lucent— opaque.     Fracture  uneven.     Thin  lami- 
nse  flexible. 


Comp.— 2HCaAs04+5aq= Arsenic  pentoxide  511,   lime 
24-9,  water  24-0=  100. 

Pyr.,  etc — In  the  closed  tube  yields  water  and  becomes 
opaque.  B.B.  in  O.F.  fuses  with  intumescence  to  a  white 
enamel,  and  colors  the  flame  light  blue  (arsenic).  On  char- 
coal in  R.  F.  gives  arsenical  fumes,  and  fuses  to  a  semi-transparent  globule,  sometimes  tinged 
blue  from  traces  of  cobalt.  The  ignited  mineral  reacts  alkaline  to  test  paper.  Insoluble  in 
water,  but  readily  soluble  in  acids. 

Obs. — Found  with  arsenical  ores  of  cobalt  and  silver  at  Wittichen,  Baden  ;  at  Andreasberg, 
and  at  Riechelsdorf  and  Bieber  ;  at  Joaohimsthal. 

This  species  was  named,  in  allusion  to  its  containing  arsenic,  from  <pdp[j.aKoj/,  poison. 

STRUVITE. — An  ammonium-magnesium  phosphate  containing  12  equivalents  of  water.  In 
guano  from  Saldanha  Bay,  Africa. 

HAIDINGERITE. — HCaAsO4+aq.=  Arsenic  pentoxide  58*1,  lime  28  "3,  water  13 '6=100. 
Joachimsthal  (?). 

BRUSIIITE.— HCaP04(R3P.Oe)+2aq=Phosphorus  pentoxide  41-3,  lime  32'6,  water  61= 
100.  Monoclinic.  Gr.  =  2  208.  On  guano  at  Aves  Island  and  Sombrero. 

METABUUSIIITE. — 2HCaP04+3aq.  GK=2'35.  Sombrero.  ORNITHRITE.  Probably  altered 
brushite. 

CHTTRCIIITE.— R3P208+4aq,  with  R=Ce(Di),Ca.     Cornwall. 

WAPPLERITE  (Frenzd). — Triclinic.  In  minute  crystals  and  in  incrustations.  Color  white. 
Composition  H^Ca,Mg)As04+7aq=(Ca  :  Mg=4  :  3)  arsenic  pentoxide  48 "7,  lime  13'5,  mag- 
nesia 7'3,  water  30  5  — 100.  Found  with  pharmacolite  at  Joachimsthal.  Schrauf  states  that 
rcesslerite  is  a  pseudomorph  after  wappierite. 

HOERNESITE. — Monoclinic.  Color  snow-white.  Composition  Mg3As.2O8-l-8aq.  From  the 
Banat. 

PiCRorHARMACOLiTE. — Monoclinic.     Ca3(Mg3)As2O8+6aq.     Riechelsdorf;  Freiberg. 


VIVTANITE. 

Monoclinic.     C  =  75°  34',  /A  1=  108°  2',  1  A 1  =  120°  26', 
•935792  :  1-33369  :  1 ;  v.  Rath.    Surface  i-l  smooth,  others 
striated.     Cleavage  :   i-l,  highly  perfect ;  i-i  and  \-i  in 
traces.     Often  reniform  and  globular.     Structure  diver- 
gent, fibrous,  or  earthy  ;  also  iucrusting. 

H.  =  1-5-2.  G-.=2-58-2-68.  Lustre,  i-l  pearly  or  me- 
tallic pearly  ;  other  faces  vitreous.  Color  white  or  color- 
less, or  nearly  so,  when  unaltered  ;  often  blue  to  green, 
deepening  on  exposure ;  usually  green  when  seen  per- 
pendicularly to  the  cleavage-face,  and  blue  transversely  ; 
the  two  colors  mingled,  producing  the  ordinary  dirty  blue 
color.  Streak  colorless  to  bluish-white,  soon  changing  to 
indigo-blue ;  color  of  the  dry  powder  often  liver-brown. 
Transparent — translucent;  becoming  opaque  on  expo- 
sure. Fracture  not  observable.  Thin  laminae  flexible. 
Sectile. 

Comp. — Fe3P2Oe+8aq=:Phosphorus  pentoxide  28'3,  iron  protoxide  43  !0,  water  28*7=1)0. 


350 


DESCRIPTIVE   MINERALOGY. 


Pyr.,  etc.— In  the  closed  tube  yields  neutral  water,  whitens  and  exfoliates.  B.B.  fuses  at 
1 '5,  coloring  the  flame  bluish- green,  to  a  grayish-black  magnetic  globule.  With  the  fluxes 
reacts  for  iron.  Soluble  in  hydrochloric  acid. 

Diff. — Distinguishing  characters  :  deep-blue  color ;   softness ;   solubility  in  acid. 

Obs. — Occurs  associated  with  pyrrhotite  and  pyrite  in  copper  and  tin  veins ;  in  beds  of 
clay,  and  sometimes  associated  with  li'i  onite,  or  bog  iron  ore;  often  in  cavities  of  fossils  or 
buried  bones.  Occurs  at  Wheal  Falmouth,  and  elsewhere  in  Cornwall ;  in  Devonshire,  near 
Tavistock ;  at  Bodenmais.  The  earthy  variety,  called  blue  iron  earth  or  native  Prussian  blue 
occurs  in  Greenland,  Carinthia,  Cornwall,  etc.  At  Cransac,  France. 

In  N.  America,  it  occurs  in  New  Jersey,  at  Allentown  ;  at  Franklin.  Also  in  Delaware,  near 
Middletown ;  near  Cape  Henlopen.  In  Maryland,  in  the  north  part  of  Somerset  and  Wor- 
cester Cos.  In  Virginia,  in  Stafford  Co.  In  Canada,  with  limonite  at  Vandreuil,  abundant. 

LUDLAMITE  (Field). — Monoclinic.  H.=3  4.  G.  =3-12.  Color  clear  green,  from  pale  to 
dark.  Transparent,  brilliant.  Composition  2Fe3P;O8  +  H2FeO2  +  8aq=Phosphorus  pentoxide 
29'88,  iron  protoxide  53'06,  water  17'06  =  100.  Cornwall. 


Monoclinic. 

678 


Schneeberg. 


ERYTHRITE.     Cobalt  Bloom.     Kobaltbliithe,  Germ. 

=  70°  54',  /A  /=  111°  16'  O  A  14  =  146°  19';  c  :  I  :  d 
=  0-9747  :  1-3818  :  1.  Surfaces  i-i  and  l-i  vertically 
striated.  Cleavage  :  i-i  highly  perfect,  i-i  and  I-i  indis- 
tinct. Also  in  globular  and  reniform  shapes,  having  a 
drusy  surface  and  a  columnar  structure  ;  sometimes  stel- 
late. Also  pulverulent  and  earthy,  incrusting. 

H.=  1-5-2-5  ;  the  lowest  on  £4*  G.  —  2-948.  Lustre 
of  i-i  pearly  ;  other  faces  adamantine,  inclining  to  vitre- 
ous ;  also  dull  and  earthy.  Color  crimson  and  peach- 
red,  sometimes  pearl-  or  greenish-gray  ;  red  tints  incline 
to  blue,  perpendicular  to  cleavage-face.  Streak  a  little 
paler  than  the  color  ;  the  dry  powder  deep  lavender- 
blue.  Transparent  —  subtranslucent.  Fracture  not  ob- 
servable.  Thin  laminae  flexible  in  one  direction.  Sectile. 


Comp.  —  Co3As208+8aq=  Arsenic  pentoxide  38'40,  cobalt  oxide  37  '56,  water  24  '04  ;  Co 
often  partly  replaced  by  Fe,Ca,  or  Ni. 

Pyr.,  etc.  —  In  the  closed  tube  yields  water  at  a  gentle  heat  and  turns  bluish  ;  at  a  higher 
heat  gives  off  arsenous  oxide,  which  condenses  in  crystals  on  the  cool  glass,  and  the  residue 
has  a  dark  gray  or  black  color.  B.B.  in  the  forceps  fuses  at  2  to  a  gray  bead,  and  colors  the 
flame  light  blue  (arsenic).  B.B.  on  charcoal  gives  an  arsenical  odor,  and  fuses  to  a  dark  gray 
arsenide,  which  with  borax  gives  the  deep  blue  color  characteristic  of  cobalt.  Soluble  in 
hydrochloric  acid,  giving  a  rose-red  solution. 

Obs.  —  Occurs  at  Schneeberg  in  Saxony  ;  at  Saalfeld  in  Thuringia  ;  Wolfach  and  Wittichen 
in  Baden;  Modum  in  Norway;  at  Allemont  in  Dauphiny;  in  Cornwall,  at  the  Botallack 
mine,  etc. 

Erythrite,  when  abundant  ,  is  valuable  for  the  manufacture  of  smalt.  Named  from  epvdpos, 
red. 

ROSELITE.  —  Triclinic  (Schrauf).  Usually  in  complex  twin  crystals.  H.  =3  '5.  G.=3'585 
-3  '738.  Color  rose-red.  Composition  RaAs208-i-2aq  (or  3aq),  with  R=Ca,Mg,  and  Co.  Ana- 
lysis, Winkler,  As,05  49'96,  CoO  12-45,  CaO  23-72,  MgO  4  '67,  H2O  9'69=100'49.  Found  at 
Schneeberg,  Saxony  ;  the  crystals  fro'm  the  Daniel  Mine  have  a  lighter  color  than  those  of  the 
Rappold  Mine,  the  latter  containing  less  cobalt  and  more  calcium. 

WINKLERITE.  —  Contains  As2O5,Cu,eo,Fe,Co,Ni,Ca,H2O,C02,  etc.  Mixture  (?).  Pria, 
Spain. 

K  )TTIGITE.  —  Near  erythrite,  but  contains  zinc.     Schneeberg. 

ANNABKKGITE  (Nickelbluthe,  Germ.}.  —  Ni3As208-l-8aq=  Arsenic  pentoxide  38'6,  nickel 
oxide  37  2,  water  24-2—100.  Soft,  earthy.  Color  apple-green.  Allemont;  Annaberg  ; 
Riechelsdorf. 

HUREAULITE.  —  A  hydrous  iron-manganese  phosphate,  occuring  in  cavities  in  triphylite 
at  Limoges,  France. 

CHONDRARSENITE.  —  Yellow  grains  in  barite  ;  probably  a  manganese  arseniate.  Paisberg, 
Sweden. 


OXYGEN   COMPOUNDS. — PHOSPHATES,    ARSENATES,    ETC. 


351 


LIBETHENITE. 

Orthorhombic.     /A  /=  92°  20',  O  A  14  =  143°  50' ;  c  :  I  :  d  =  0-7311 
:  1*0416  :  1.      Crystals    usually    octahedral    in    aspect. 
Cleavage :  diagonal,  i-i,  i-l,  very  indistinct.     Also  globu- 
lar or  reniform,  and  compact. 

II.  =4.  G.=3'6-3*8.  Lustre  resinous.  Color  olive- 
green,  generally  dark.  Streak  olive-green.  Translucent, 
to  subtranslucent.  Fracture  subconchoidal — uneven. 
Brittle. 


Comp. — Cu4P2O9-+-aq,  or  CusPoOs-f-H^CuOa  (Ramm.)= Phosphorus 
pentoxide  29 •?,  copper  oxide  66 '5,  water  3 '8= 100. 

Pyr.,  etc. — In  the  closed  tube  yields  water  and  turns  black.  B.B. 
fuses  at  2  and  colors  the  flame  emerald-green.  On  charcoal  with  soda 
gives  metallic  copper,  sometimes  also  an  arsenical  odor.  Fused  with 
metallic  lead  on  charcoal  is  reduced  to  metallic  copper,  with  the  forma- 
tion of  lead  phosphate,  which  treated  in  R.F.  gives  a  crystalline  polyhedral  bead  on  cooling. 
With  the  fluxes  reacts  for  copper.  Soluble  in  nitric  acid. 

Obs. — Occurs  at  Libethen,  in  Hungary ;  at  Rheinbreitenbach  and  Ehl  on  the  Rhine ;  at 
Nischne  Tagilsk  in  the  Ural ;  in  Bolivia  ;  Chili. 


OLIVENITE. 

Orthorhombic.  /A  7=  92°  30',  0  A  1-*  =  1M°  14' ;  c 
1*0446  :  1.  Cleavage:  7  and  14  in  traces.  Sometimes  aci- 
cular.  Also  globular  and  reniforrn,  indistinctly  fibrous, 
fibres  straight  and  divergent,  rarely  promiscuous;  also 
curved  lamellar  and  granular. 

H.=3.  G.=4-l-4-4.  Lustre  adamantine — vitreous;  of 
some  fibrous  varieties  pearly.  Color  various  shades  of  olive- 
green,  passing  into  leek-,  siskin-,  pistachio-,  and  blackish- 
green  ;  also  liver-  and  wood-brown  ;  sometimes  straw-yellow 
and  grayish-white.  Streak  olive-green — brown.  Subtrans- 
parent — opaque.  Fracture,  when  observable,  conchoidal — 
uneven.  Brittle. 


Comp.— Cu4As209+aq:=Cu3As2O8+H2Cu02  (Bamm.)=  Arsenic  pentoxide  40'66,  copper 
oxide  5615,  water  3-19=100. 

Pyr.,  etc. — In  the  closed  tube  gives  water.  B.B.  fuses  at  2,  coloring  the  flame  bluish-green, 
and  on  cooling  the  fused  mass  appears  crystalline.  B.B.  on  charcoal  fuses  with  deflagration, 
gives  off  arsenical  fumes,  and  yields  a  metallic  arsenide,  which,  with  soda  yields  a  globule  of 
copper.  With  the  fluxes  reacts  for  copper.  Soluble  in  nitric  acid. 

Obs. — The  crystallized  varieties  occur  in  many  of  the  Cornwall  mines ;  near  Tavistock  in 
Devonshire  ;  also  at  Alston  Moor  in  Cumberland  ;  at  Camsdorf  and  Saalfeld  in  Thuringia  ;  the 
Tyrol ;  the  Bannat ;  Siberia  ;  Chili ;  and  other  places. 

ADAMITE.— Zn3As2O8+HoZnO.,=:Arsenic  pentoxide  40'2,  zinc  oxide  56 '7,  water  31=100. 
Color  yellow.  Chanarcillo,  Chili ;  Cap  Garonne. 

TAOTLITE — Cu4P2O9  +  3aq  (  =  Cu3P2O8+H2CuO2+2aq).  Color  emerald-green.  Nischne- 
Tagilsk.  ISOCLASITE.  Ca4P2O9+5aq  (  =  Ca3P2O8  +  H2CaO2  +  4aq).  Colorless  to  snow-white. 
Joachimsthal. 

EucimoifE. — CuaAsoOg+HjCuOa+Baq  (Ramm.)= Arsenic  pentoxide  34 '1,  copper  oxide 
47'2,  water  18'7=100.  Color  emerald-green.  Libethen,  Hungary. 

CIILOKOTILE.—  Cu3As20«-|-6aq.  In  capillary  crystals.  Also  fibrous ;  massive.  Color  apple- 
green.  In  quartz  at  Schneeberg  and  Zinnwald  ;  Thuringia  ;  Chili  (Frenzel). 

VESZELYITE  (Schravf). — A  hydrous  copper  phosphate  ;  composition  4Cu3P208+ 5aq.  Tri- 
clinic.  Occurs  in  crystalline  crusts  on  a  garnet-rock  at  Morawicza  in  the  Bannat. 


352 


DESCRIPTIVE   MINERALOGY. 


LIROCONITE.    Linsenerz,  Germ. 

Monoclinic.  /A 7=74°  21',  DesCl.  C  =  88°  33'.  Cleavage  lateral, 
but  obtained  with  difficulty.  Rarely  granular. 

H.  — 2-2-5.  G.  =  2'88-2'9<8.  Lustre  vitreous,  inclining  to  resinous. 
Color  and  streak  sky-blue — verdigris-green.  Fracture  imperfectly  cou- 
choidal,  uneven.  Imperfectly  sectile.  • 

Comp.— Formula  Cu3(A-l)  As2(Pa)08+H6(Cu3,Al)06-l-9aq,  with  Cu3  :  Al=3  :  2,  and  As  : 
P=l  :  4.  This  requires  arsenic  pentoxide  231,  phosphorus  pentoxide  3'6c,  opper  oxide  35*9, 
alumina  10 '3,  water  27 '1=1 00. 

Pyr.,  etc. — In  the  closed  tube  gives  much  water  and  turns  olive-green.  B.B.  cracks  open, 
but  does  not  decrepitate  ;  fuses  less  readily  than  olivenite  to  a  dark  gray  slag ;  on  charcoal 
cracks  open,  deflagrates,  and  gives  reactions  like  olivenite.  Soluble  in  nitric  acid. 

Obs. — With  various  ores  of  copper,  pyrite,  and  quartz,  at  Wheal  Gorland,  Wheal  Muttrell, 
etc..  in  Cornwall;  also  in  minute  crystals  at  Herrengrund  in  Hungary ;  and  in  Voigtland. 

PSEUDOMALACHITE  PJiosphochaltite.  —  Cu6P2O11+3aq=Cu3PiO8+3H2CuO2  =  PiO,  21  1, 
CuO  70 '9,  H.2O  8'0— 100.  Triclinic  (Schrauf).  G.=:4*34.  Color  emerald-green.  Related 
sub-species:  EHLITE  (Prasine),  Cu3P2O8+2H<.2CuO2  +  aq  (Ramm. ) ;  DIHYDIUTE,  CusP^Oa-i- 
2H2Cu02.  Ehl,  near  Linz,  on  the  Rhine  ;  Libethen,  Hungary;  Nischne  Tagilsk  ;  Cornwall. 

EKINITE. — Cu3As2O8+2H2Cu02.  In  mammillated  crystalline  groups.  Color  green.  Corn- 
wall. 

COKNWALLITE. — Cu6As2Oio+3aq  (=Cu3As208+2H2Cu02  +  aq).  Amorphous.  Color  green. 
Cornwall  (Church}. 

PsiTTAClNTTE. — Occurs  in  thin  crypto-crystalline  coatings,  sometimes  having  a  botryoidal 
structure;  also  pulverulent.  Color  siskin -green  to  olive-green.  Formula  2R3V2O8  -I-  3H2CuOj 
+6aq,  withR^Pb  :  Cu=3  :  1.  This  requires  :  Vanadium  pentoxide  19 '32,  lead  oxide  5315, 
copper  oxide  18*95,  water  8-58=100.  Found  at  the  gold  mines  in  Silver  Star  District,  Mon- 
tana (Genth.  Am.  J.  Sci.,  III.,  xii.,  35,  1870). 

MOTTRAMITE. — Occurs  as  a  thin  crystalline  incrustation,  which  is  sometimes  velvety,  con- 
sisting of  minute  crystals  ;  more  generally  compact.  H.  — 3.  G-.  =5 '894.  Color  black  by 
reflected  light,  in  thin  particles  yellowish,  translucent  (crystals) ;  purplish-brown,  opaque, 
(compact).  Formula  (Pb,Cu)3V2O84-2H2(Pb,Cu)O2,  which  requires  vanadium  pentoxide  18*74, 
copper  oxide  20'39,  lead  oxide  57*18,  water  3'69=100.  Related  to  dihydrite  and  erinite. 
Found  in  Keuper  sandstone  at  Aldeley  Edge  and  Mottram  St.  Andrew's,  in  Cheshire,  England 
(Roscoe,  Proc.  Roy.  Soc.,  xxv.,  III.,  187(5). 

VOLBORTIIITE. — R4V2Ol)-t-aq,  with  R=Ca  :  Cu=:2  :  3  (or  3  :  7),  Ramm.  From  the  Urals. 
Kalk-volborthit  (Germ.},  Friedrichsrode,  contains  calcium. 


Monoclinic. 


681 


Color  pale  apple-green. 


CLINOOLASITE.     Strahlerz,  Germ. 

C=  80°  30',  /A/,  front,  =  56°.  Cleavage  :  basal,  highly 
perfect.  Also  massive,  hemispherical,  or  reniform  ; 
structure  radiated  fibrous. 

H.  =  2-5-3.  G.=4r-19-4-36.  Lustre:  0  pearly; 
elsewhere  vitreous  to  resinous.  Color  internally  dark 
verdigris-green;  externally  blackish-blue  green.  Streak 
bluish-green.  Subtranslucent.  Not  very  brittle. 


Comp.— Cu3As2O8-!-3H2Cu02=:Arsenic  pentoxide  30*2,  copper 
oxide  62*7,  water  7  1=100. 

Pyr.,  etc. — Same  as  for  olivenite. 

Obs. — Occurs  in  Cornwall,  with  other  ores  of  copper,  at  several 
mines.  Also  found  in  the  Erzgebirge. 

TYROLITE  (Kupferschaum). — A  hydrous  arsenate  of  copper  (Cu5 
As2Oio  +  waq),  containing  also  calcium  carbonate  (as  an  impurity  ?  ). 
Libethen,  Hungary ;  Schneeberg,  etc. 


OXYGEN   COMPOUNDS. PHOSPHATES,    AKSENATES,    ETC, 


353 


CHALCOPHYLLITE  (Copper  mica  ;  Kupferglimmer,  Germ.).— Cu3As208+5H2CuO2 
Arsenic  pentoxide  21 '3,  copper  oxide  58 '7,  water  20 '0=100.     Copper  mines  of  Cornwall; 
Hungary;  Moldawa. 


LAZULITE.     Blauspath,  Germ. 

Monoclinic.  C  =  88°  15',  1 A  1  =  91°  30',  O  A  l-l  =  139°  45 ',  Priifer ; 
c:b:d  =  0-86904: :  1*0260  :  1.  Twins :  twiiming-plane  i4\  also  O.  Cleav- 
age :  lateral,  indistinct.  Also  massive. 

683  684 


-2 


G-.— 3*057,  Fiichs.  Lustre  vitreous.  Color  azure-blue ;  com- 
monly a  fine  deep  blue  viewed  along  one  axis,  and  a  pale  greenish-blue 
along  another.  Streak  white.  Subtranslucent — opaque.  Fracture  uneven. 
Brittle. 

Comp.— RAlP2O9+aq=AlP208+H2(Mg,Fe)02  (Dana) = Phosphorus  pentoxide  46 '8,  alu- 
mina 34-0,  magnesia  13  "2,  water  6 '0=100. 

Pyr.,  etc. — In  the  closed  tube  whitens  and  yields  water.  B.B.  with  cobalt  solution  the 
blue  color  of  the  mineral  is  restored.  In  the  forceps  whitens,  cracks  open,  swells  up,  and 
without  fusion  falls  to  pieces,  coloring  the  flame  bluish-green.  The  green  color  is  made  more 
intense  by  moistening  the  assay  with  sulphuric  acid.  With  the  fluxes  gives  an  iron  glass ; 
with  soda  on  charcoal  an  infusible  mass.  Unacted  upon  by  acids,  retaining  perfectly  its  blue 
color. 

Diff. — Characterized  by  its  fine  blue  color;  blue  flame  B.B. 

Obs. — Occurs  near  Werf  en  in  Salzburg ;  in  Gratz,  near  Vorau  ;  in  Krieglach,  in  Styria ;  at 
Hochthaligrat,  at  the  Gorner  glacier,  in  Switzerland  ;  in  Horrsjoberg,  Wermland  ;  Westana, 
Sweden;  also  at  Tijuco  in  Minas  Geraes,  Brazil.  Abundant  at  Crowder's  Mt.,  Lincoln  Co., 
N.  C.;  and  on  Graves  Mt.,  Lincoln  Co.,  Ga.,  50  m.  above  Augusta. 


SCORODITE. 


7A7=98°  2',  O  A 14  =  132°  20';  c 
Cleavage  :  i-%  imperfect,  i-%  and  i-i  in 


Orthorhombic. 
1-1511  :  1,  Miller, 
traces. 

H.=3'5-4.  G.=3'l-3*3.  Lustre  vitreous — subadaman- 
tine  and  subresinous.  Color  pale  leek-green  or  liver-brown. 
Streak  white.  Subtransparent — translucent.  Fracture 
uneven. 

Comp. — FeAs2O8-f4aq=Arsenic  pentoxide  49'8,  iron  sesquioxide 
34'6,  water  15'6=100. 

Pyr.,  etc. — In  the  closed  tube  yields  neutral  water  and  turns  yellow. 
B.B.  fuses  easily,  coloring  the  flame  blue.  B.B.  on  charcoal  gives 
arsenical  fumes,  and  with  soda  a  black  magnetic  scoria.  With  the  fluxes 
reacts  for  iron.  Soluble  in  hydrochloric  acid. 

23 


l\d  =  1-0977 


354  DESCRIPTIVE   MINERALOGY. 

Obs  —  Found  at  Schwarzenberg  in  Saxony  ;  at  Nertschinsk,  Siberia  ;  Dernbach  in  Nassau  ; 
in  the  Cornish  mines  ;  at  the  Minas  Geraes,  in  Brazil  ;  in  Popayan  ;  at  the  gold  mines  of  Vic- 
toria in  Australia.  Occurs  in  minute  crystals  and  druses,  near  Edenville,  N.  Y.  ;  in  Cabarras 
Co.,  N.  C. 

WAVELLITE. 

Orthorhombic.  /A  /=  126°  25',  O  A  14  =  143°  23'  ;  c  :  I  :  a  =  0-7431 
:  1-4943  :  1.  Cleavage  :  /  rather  perfect  ;  also  brachy  dia- 
gonal. Usually  in  hemispherical  or  globular  concretions, 
having  a  radiated  structure. 

II.  =  3-25-4.  G.  =  2-316-2-337.  Lustre  vitreous,  inclin- 
ing to  pearly  and  resinous.  Color  white,  passing  into  yel- 
low, green,  gray,  brown,  and  black.  Streak  white.  Trans- 
lucent. 


Comp.  —  Al3P4O19,12aq=2AlP2O8  +  H2AlO6+9aq=r  Phosphorus  pentox- 
ide3516,  alumina  3810,  water  26  '74—  100  ;  1  to  2  p.  c.  fluorine  are  often 
present,  replacing  the  oxygen. 

Pyr.,  etc.  —  In  the  closed  tube  gives  off  much  water,  the  last  portions 
of  which  react  acid  and  color  Brazil-wood  paper  yellow  (fluorine),  and 
also  etch  the  tube.  B  B.  in  the  forceps  swells  up  and  splits  frequently  into  fine  acicular 
particles,  which  are  infusible,  but  color  the  flame  pale  green  ;  moistened  with  sulphuric  acid 
the  green  becomes  more  intense.  Gives  a  blue  with  cobalt  solution.  Some  varieties  react 
for  iron  and  manganese  with  the  fluxes.  Heated  with  sulphuric  acid  gives  off  fumes  of  fluo- 
hydric  acid,  which  etch  glass.  Soluble  in  hydrochloric  acid,  and  also  in  caustic  potash. 

Diff.  —  Distinguished  from  the  zeolites  and  from  gibbsite  by  its  giving  a  phosphorus  reac- 
tion ;  it  dissolves  in  acid  without  gelatinization. 

Obs.  —  Found  near  Barnstable,  Devonshire;  at  Clonmel  and  Cork,  Ireland;  in  the  Shaint 
Isles  of  Scotland  ;  at  Zbirow  in  Bohemia  ;  Zajecov  in  Bohemia  ;  at  Frankenberg-  and  Langen- 
striegis,  Saxony;  Diensberg,  near  Giessen,  Hesse  Darmstadt;  in  a  manganese  mine  in  Wein- 
bach,  near  Weilburg,  in  Nassau  ;  at  Villa  Rica,  Minas  Geraes,  Brazil.  In  the  United  States. 
at  the  slate  quarries  of  York  Co.,  Pa.;  at  Washington  mine,  Davidson  Co.,  N.  C.;  at  White 
Horse  Station,  Chester  Co.,  Pa.;  Magnet  Cove,  Ark. 

ZEPIIAKOVICHITE.  —  Near  wavellite.  Composition  A1P2O8  +  6aq  (or  5aq,  Ramm.).  Compact. 
•Color  greenish  to  grayish.  Occurs  in  sandstone  at  Trenic,  Bohemia. 

CCERULEOLACTITE.  —  Crypto-crystalline.  Color  milk-white  to  light  blue.  Composition 
{Petersen)  Al3P4Oi9  +  10aq.  Katzenellnbogen.  Nassau.  Also  Chester  Co.,  Penn.  (Genth, 
who  regards  the  copper,  4  p.  c.,  as  belonging  to  the  mineral.) 

PHARMACOSIDERITE.    Wiirfelerz,  Germ. 

Isometric  ;  tetrahedral.  Crystals  modified  cubes  and  tetrahedrons. 
Cleavage:  cubic,  imperfect.  0  sometimes  striated  parallel  to  its  edge  of 
intersection  with  plane  1  ;  planes  often  curved.  Rarely  granular. 

H.  —  2-5.  G.  =  2-9-3.  Lustre  adamantine  to  greasy,  not  very  distinct. 
Color  olive-green,  passing  into  yellowish-brown,  bordering  sometimes  upon 
hyacinth-red  and  blackish  -brown  ;  also  passing  into  grass-green,  emerald- 
green,  and  honey-yellow.  Streak  green  —  brown,  yellow,  pale.  Subtrans- 
parent  —  subtranslucent.  Rather  sectile.  Pyroelectric. 

Comp  —  Fe4As6O_>7,15aq=3FeAs2O8+H6FeO6  (Ramm.  )=  Arsenic  pentoxide  4313,  iron 
eesquioxide  40  '00,  water  16  '87=100. 

Pyr.,  etc.  —  Same  as  for  scorodite.    ' 

Obs.-  -Formerly  obtained  at  the  mines  of  Wheal  Gorland,  Wheal  Unity,  and  Carharrack, 
in  Cornwall  ;  now  found  at  Burdle  Gill  in  Cumberland  ;  in  minute  tetrahedral  crystals  at 
Wheal  Jane  ;  also  in  Australia  ;  at  St.  Leonard  in  France  ;  and  at  Schneeberg  and  Schwar- 
zenberg in  Saxony. 


OXYGEN   COMPOUNDS. PHOSPHATES,    AKSENATES,   ETC.  355 

Named  from  <t>dp/j.aKov,  poison  (in  allusion  to  the  arsenic  present),  and  crl8r]po\,  iron.  Wurfel- 
erz,  of  the  Germans,  means  cube-ore. 

RHAGITE  (Weisbach). — Composition  BiioAH4O25+9aq=2BiAs04+3HaBiO3=Arsemc  pent- 
oxide  15'6,  bismuth  oxide  78'9,  water  5'5=100.  Spherical  crystalline  aggregates.  Color 
bright  green.  Schneeberg,  Saxony. 

PLUMBOGUMMITE. — Composition  uncertain.  Contains  essentially  alumina,  lead,  water, 
and  phosphorus  pentoxide.  Huelgoet ;  Cumberland  ;  Mine  la  Motte,  Mo. 


CHILDRENITE. 

Orthorhombic.     1 A  1=  111°  54',  O  A  14  =  136°  26' ;  c:b:d  =  0-9512 
:  1-4798  :  1.     Plane   O  sometimes  wanting,  and  the  form  a  double  six- 
-sided pyramid,  made  up  of  the  planes  1,  2-£,  with  i-l  small.     Cleavage  :  i-$, 
imperfect. 


II. =4-5-5.  G.— 3-18-3-24  Lustre  vitreous,  inclining  to  resinous. 
Color  yellowish-white  and  pale  yellowish-brown,  also  brownish-biack. 
Streak  white,  yellowish.  Translucent.  Fracture  uneven. 

Comp. — Formula  somewhat  uncertain.  Analysis:  Rammelsberg,  P2O5  28 '92,  A103 14 '44, 
FeO  30-68,  MnO  9 "07,  MgO  0'14,  H2O  16-98=100  "23. 

Pyr.,  etc. — In  the  closed  tube  gives  off  neutral  water.  B.B.  swells  up  into  ramifications, 
and  fuses  on  the  edges  to  a  black  mass,  coloring  the  flame  pale  green.  Heated  on  charcoal 
turns  black  and  becomes  magnetic.  With  soda  gives  a  reaction  for  manganese.  With  borax 
and  salt  of  phosphorus  reacts  for  iron  and  manganese.  Soluble  hi  hydrochloric  acid. 

Obs. — Occurs  near  Tavistock ;  also  at  Wheal  Crebor,  in  Devonshire ;  on  slate  at  Crinnis 
mine  in  Cornwall. 


TURQUOIS.     Callaite.     Kallait,  Kalait,  Germ. 

Reniform,  stalactitic  or  incrusting.     Cleavage  none. 

H.:=6.  G.  =  2-6-2-83.  Lustre  somewhat  waxy,  feeble.  Color  sky-blue, 
bluish-green  to  apple-green.  Streak  white  or  greenish.  Feebly  subtrans- 
Incent — opaque.  Fracture  small  conchoidal. 

Comp. — Hydrous  aluminum  phosphate,  perhaps  A^PoOn+Saq^Phosphorus  pentoxide 
32-6,  alumina  46 -9,  water  20-5  =  100 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  yields  water,  and  turns  brown  or  black.  B.B. 
in  the  forceps  becomes  brown  and  assumes  a  glassy  appearance,  but  does  not  fuse ;  colors 
the  flame  green;  moistened  with  hydrochloric  acid  the  color  is  at  first  blue  (copper  chloride). 
With  the  sodium  test  gives  phosphuretted  hydrogen.  With  borax  and  salt  of  phosphorus  gives 
beads  in  O.F.  which  are  yellowish  green  while  hot,  and  pure  green  on  cooling.  With  salt  of 
phosphorus  and  tin  on  charcoal  gives  an  opaque  red  bead  (copper).  Soluble  in  hydrochloric 
acid. 

Obs — Occurs  in  clay  slate  in  a  mountainous  district  in  Persia,  not  far  from  Mchabour. 
According  to  Agaphi,  the  only  naturalist  who  has  visited  the  locality,  turqnois  occurs  only  in 
veins,  which  traverse  the  mountain  in  all  directions.  An  impure  variety  is  found  in  Silesia, 


356  DESCRIPTIVE   MINERALOGY. 

and  at  Oelsnitz  in  Saxony.  W.  P.  Blake  refers  here  a  hard  yellowish-  to  bluish-green  stone 
(which  he  identifies  with  the  chalcMhuitl  of  the  Mexicans]  from  the  mountains  Los  Cerillas. 
20  in.  S.  E.  of  Santa  Fe.  A  pale  green  turquois  occurs  in  the  Columbus  district,  Nevada. 

Turquois  receives  a  good  polish,  and  is  highly  esteemed  as  a  gem.  The  Persian  king  is 
said  to  retain  for  his  own  use  all  the  larger  and  finely  tinted  specimens. 

PEGANITE. — Composition  Al2P2O8+6aq=Phosphorus  pentoxide  311,  alumina  31 1,  water 
23-7=100.  Striegis,  Saxony  ;  Arkansas. 

DUFRENITE.—  Composition  Fe2P2O8+3aq  (FeP2O8+H6FeOB)=Phcsphorus  pentoxide  27-5, 
iron  sesquioxide  62*0,  water  10 '5 =100.  Anglar,  Dept.  of  Haute  Vienne  ;  Hirschberg,  West- 
phalia ;  Allentown,  3ST.  J.  In  deposits  of  nodules  1  to  6  in.  thick,  in  Rockbridge  Co. ,  Va. 

ANDREWSITE. — In  globular  forms,  having  a  radiated  structure.  H.  =4.  G-.=3'475. 
Color  dark  green.  Analysis,  Flight,  P205  26-09,  FeO3  44-64,  frl03  0"92,  CuO  10'86,  FeO  711, 
MnO  0-60,  CaO  0'09,  SiO2  0'49,  H20  8 -79 =99 '59.  In  a  tin  lode,  West  Phenix  mine,  near 
Liskeard,  Cornwall. 

CHALCOSIDERITE. — In  bright  green  crystals  (triclinic)  on  Andrewsite  (see  above).  H.  = 
4-5.  Gr.=3108.  Analysis,  Flight,  P2O5  29D3,  As205  0'61,  FeO3  42'81,  A1O3  4-45,  CuO  814,, 
H2O  15-00,  UO  tr.  =100-94.  Also  as  a  coating  on  dufrenite.  Cornwall.  Sayn,  Westphalia. 

HENWOODITE. — In  globular  forms,  with  a  radiated,  structure.  H.=4-4'5.  G-.=2'67. 
Color  turquois-blue  to  bluish-green.  B.B.  infusible.  Analysis,  P2O5  48'94,  A1O3  18*24 
FeO3'2-74,  CuO  710,  CaO  0'54,  H2O  1710,  Si02  1-37,  loss  3'97=100.  Occurs  on  limonite  at 
the  West  Phenix  mine,  Cornwall  (Collins,  Min.  Mag.,  1,  p.  11). 

CACOXENITE. — Supposed  to  be  an  iron  wavellite.  Composition  Fe2P2O8-fl2aq.  In  radiated 
tufts.  Color  yellow.  Hrbeck  mine,  Bohemia. 

ARSENIOSIDERITE.— Analysis  by  Church,  As2O5  39 "86,  Fe03  35-75,  CaO  15'53,  MgO  0'18, 
K,O  0-47,  H2O  7-87=9966.  Formula  (Ramm.)  2Ca3As.O8  +  FeAs2O8  +  3HGFeOB.  Ro- 
maneche. 

ATELESTITE. — Essentially  a  bismuth  arsenate.      In  minute  yellow  crystals  at  Schneeberg. 


TORBERNITE.    Chalcolite.     Kupfer-Uranit,  Germ. 

Tetragonal.  O  A  14  =  134°  8' ;  c  —  1-03069.  Forms  square  tables,  with 
often  replaced  edges  ;  rarely  suboctahedral.  Cleav- 
age :  basal  highly  perfect,  micaceous.  Unknown 
massive  or  earthy. 

H.  =  2-2-5.     G.  =  3-4-3-6.     Lustre  of  O  pearly,  of 
other  faces   subadamantine.      Color  emerald-   and 
grass-green,  and  sometimes  leek-,  apple-,  and  sis- 
Cornwall,  kin-green.     Streak  somewhat  paler  than  the  color. 
Transparent — subtranslncent.      Fracture    not    ob- 
servable.    Sectile.     Laminse  brittle  and  not  flexible.     Optically   uniaxial ; 
double  refraction  negative. 

O 

Comp.  - Q.  ratio  for  R  :  IT  :  P  :  0=1  :  6  :  5  :  8 ;  formula  CuU2P2Oi2  +  8aq=2(U02)3P,O8 
+  Cu3P..iO8-|-24aq.  The  formula  requires:  Phosphorus  pentoxide  151,  uranium  trkxide 
61*2,  copper  oxide  8'4,  water  15'3  =  100. 

Pyr.,  etc. — In  the  closed  tube  yields  water.  In  the  forceps  fuses  at  2 "5  to  a  blackish  mass, 
and  colors  the  flame  green.  With  salt  of  phosphorus  gives  a  green  bead,  which  with  tin  on 
charcoal  becomes  on  cooling  opaque  red  (copper).  With  soda  on  charcoal  gives  a  globule  of 
copper.  Affords  a  phosphide  with  the  sodium  test.  Soluble  in  nitric  acid. 

Obs. — Ghmnis  Lake,  Tincroft  and  Wheal  Buller,  near  Redrutb,  and  elsewhere  in  Cornwall. 
Found  also  at  Johanngeorgenstadt,  Eibenstock,  and  Schneeberg,  in  Saxony  ;  in  Bohemia,  at 
Joachimsthal  and  Zinnwald ;  in  Belgium,  at  Vielsalm. 

Both  this  species  and  the  autunite  have  gone  under  the  common  name  of  uranite }  the 
former  also  as  Copper-uranite,  the  latter  Lime-wanite. 


OXYGEN   COMPOUNDS. PHOSPHATES,    ARSENATES,    ETC.  35 7 


AUTUNITE.     Uranit;  Kalk-Uranglimmer,  Kalk-Uranit,  Germ. 

Orthorhombic ;  but  form  very  nearly  square,  and  crystals  resembling 
closely  those  of  torbernite.  Cleavage :  basal  eminent,  as  in  torbernite. 

H.  =  2-2'5.  Gr.=:3'05-3€19.  Lustre  of  O  pearly  ;  elsewhere  subadaman- 
tine.  Color  citron-  to  sulphur-yellow.  Streak  yellowish.  Translucent. 
Optically  biaxial,  DesCl. 

Comp.— Q.  ratio  for  R  :  U  :  P  :  H=l  :  6  :  5  :  10.  Formula  CaU2P2O12  +  10aq,  which  may 
be  written  2(UO2)3P208-t-Ca3P2O8+30aq.  The  formula  requires  :  Phosphorus  pentoxide  14*9, 
uranium  trioxide  (UO3)  6O4,  lime  5'9,  water  18 '8=100. 

Pyr.,  etc.— Same  as  for  torbernite,  but  no  reaction  for  copper. 

Obs.  — Occurs  at  Johanngeorgenstadt ;  at  Lake  Onega,  Wolf  Island,  Russia;  near  Limoges; 
near  Autun  ;  formerly  at  South  Basset,  Wheal  Edwards,  and  near  St.  Day,  England.  Occurs 
sparingly  at  Middletown,  Ct.  ;  also  in  minute  crystals  at  Chesterfield,  Mass. ;  at  Acworth, 
N.  H. 

TROGERITE. — Composition  U3As2Oi4-hl2aq=(TJ02)3As2O8  +  12aq.  This  requires  :  Arsenic 
pentoxide  17-6,  uranium  trioxide  65 '9,  water  16'5=100.  Monoclinic.  In  thin  tabular  crys- 
tals of  a  lemon-yellow  color.  Schneeberg,  Saxony. 

WALPURGITE.— Composition  Bi1oy3As4O34  +  12aq=(U02)3As208-f2BiAs04  +  8H3Bi03.  This 
requires  :  Arsenic  pentoxide  11 '9,  bismuth  oxide  60'0,  uranium  trioxide  22'4,  water 5 -7=100. 
Monoclinic.  In  thin  scaly  crystals.  Color  wax-yellow.  Schneeberg,  Saxony. 

URANOSPINITE. — An  arsenic  autunite.  Composition  CaU2As,O12  +  8aq=2(U02)aAs2O8  + 
Ca3As2OH-f-24aq=Arsenic  pentoxide  22'9,  uranium  trioxide  57 '2,  lime  5 '6,  water  14 '3 =100. 
Color  green.  Schneeberg,  Saxony.  URANOsrH^RiTE.  Color  yellow.  Analysis,  Winkler : 
U2Oa  50-88,  Bi203  44-34,  H2O  4-75.  Schneeberg. 

ZEUNERITE. — According  to  Winkler,  an  arsenic  chalcolite,  with  which  it  is  isomorphous. 
Composition  CuU"2As..2Oi2+8aq=2(U02)3As208  +  Cu3As208-f24aq=Arsenic  pentoxide  22'3, 
uranium  trioxide  56 '0,  copper  oxide  7 '7,  water  14-0=100.  Color  bright  green.  Schneeberg, 
Zinnwald,  Saxony;  Cornwall. 

PITTICITE. — Iron-sinter.  Composition  uncertain,  contains  As205,  Fe03,  S03,  H2O.  DIA- 
DOCHITE  is  similar,  but  contains  P2O5  instead  of  As206. 


HYDROUS    ANTIMONATES. 

BINDHEIMITE  (Bleiniere). — Amorphous,  reniform,  or  spheroidal ;  also  earthy  or  incrusting. 
H.=4.  G.  =4'60-4-76.  Color  white,  gray,  brownish,  yellowish.  Composition  uncertain; 
analysis  by  Hermann  :  Sb2O5  31-71,  PbO  61 '83,  H2O  6 '46=100.  Results  from  the  decompo- 
sition of  other  antimonial  ores.  From  Nertschinsk  in  Siberia ;  Horhausen ;  near  Endellion 
in  Cornwall,  with  jamesonite,  from  which  it  is  derived. 


NITRATES. 

The  nitrates  are  all  soluble,  and  hence  are  rarely  met  with  in  nature.     They  include  : 

NITRE,  potassium  nitrate  (KNO3).  Found  generally  in  crusts  on  the  surface  of  the  soil,  on 
walls,  rocks,  etc.  Also  found  in  numerous  caves  in  the  Mississippi  Valley. 

SODA  NITRE,  sodium  nitrate  (NaNO3).     Tarapaca,  Chili. 

NITROCALCITE.  calcium  nitrate  (CaN2O6).  Occurs  in  silky  efflorescences  in  limestone 
caverns. 

NITROMAGNESITE,  magnesium  nitrate  (MgN206).  From  limestone  caves.  NITRO- 
GLAUBERITE,  nitro -sulphate  of  sodium.  Desert  of  Atacama,  Chili. 


358  DESCRIPTIVE   MINERALOGY. 


4.  BOKATES. 


SASSOLITE. 

Triclinic.  1 A 1'  =  118°  30',  O  A  /=  95°  3',  O  t\  I'  =  80°  33',  B.  &  M. 
Twins:  composition-face  O.  Cleavage:  basal  very  perfect.  Usually  in 
small  scales,  apparently  six-sided  tables,  and  also  in  stalactitic  forms,  com- 
posed of  small  scales. 

H.— 1.  G.  =  1'48.  Lustre  pearly.  Color  white,  except  when  tinged 
yellow  by  sulphur;  sometimes  gray.  Feel  smooth  and  unctuous.  Taste 
acidulous,  and  slightly  saline  and  bitter. 

Comp.—H6B2O6=Boron  trioxide  (B2O3)  56'46,  water  43'54=100.  The  native  stalactitic 
salt  contains,  mechanically  mixed,  various  impurities,  as  sulphate  of  magnesium  and  iron, 
sulphate  of  calcium,  silica,  etc. 

Pyr.,  etc. — In  the  closed  tube  gives  water.  B.  B.  on  platinum  wire  fuses  to  a  clear  glass 
and  tinges  the  flame  yellowish-green.  Soluble  in  water  and  alcohol. 

Obs. — First  detected  in  nature  by  Hofer  in  the  waters  of  the  Tuscan  lagoons  of  Monte 
Kotondo  and  Castelnuovo,  and  afterward  in  the  solid  state  at  Sasso  by  Mascagni.  The  hot 
vapors  of  the  lagoons  consist  largely  of  it.  Exists  also  in  other  natural  waters,  as  at  Wies- 
baden ;  Aachen;  Krankenheil  near  Folz  ;  Clear  Lake  in  Lake  Co.,  California;  and  it  has 
been  detected  in  the  waters  of  the  ocean.  Occurs  also  abundantly  in  the  crater  of  Vuleano, 
one  of  the  Lipari  islands,  forming  a  layer  on  sulphur  and  about  the  fumaroles,  where  it  was 
discovered  by  Dr.  Holland  in  1813. 


SUSSEXITE  (Brush). 

In  fibrous  seams  or  veins. 

H.  =  3.  G.=3'42.  Lustre  silky  to  pearly.  Color  white,  with  a  tinge  of 
pink  or  yellow.  Translucent. 

Comp. — R.2B206+aq,  with  R:=Mn  :  Mg=4  :  3=Boron  trioxide  34*3,  manganese  protoxide 
89-9,  magnesia  16 -9,  water  8 '9  =  100. 

Pyr.,  etc. — In  the  closed  tube  darkens  in  color  and  yields  neutral  water.  If  turmeric  paper 
is  moistened  with  this  water  and  then  with  dilute  hydrochloric  acid  it  assumes  a  red  color 
(boron).  Fuses  in  the  flame  of  a  candle,  and  B.B.  in  O.F.  yields  a  black  crystalline  mass 
coloring  the  flame  intensely  yellowish-green.  Keacts  for  manganese  with  the  fluxes.  Soluble 
in  hydrochloric  acid. 

Obs. — Found  on  Mine  Hill,  Franklin  Furnace,  Sussex  Co.,  N.  J.;  associated  with  franklin- 
ite,  zincite,  willemite,  and  other  manganese  and  zinc  minerals. 

SZAIBELYITE.— A  hydrous  magnesium  borate,  Mg5B4On+3aq  (or  faq).  Occurs  in  acicular 
crystals.  Color  white.  Hungary. 

LUDWIGITE  (Tschennak}.—  Finely  fibrous  masses.  H.=5.  G.=3'907-4'016.  Color  black- 
ish-green to  black.  Composition  E4FeB2Oi0,  with  R=Fe  :  Mg=l  :  5,  or  1  :  3.  For  the 
latter  the  formula  requires  :  Boron  trioxide  16 '6,  iron  sesquioxide  37 -9.  iron  protoxide  17'1, 
magnesia  28 '4.  Occurs  in  a  crystalline  limestone  with  magnetite  at  Morawitza  in  the  Bannat. 
Also  altered  to  limonite. 


OXYGEN    COMPOUNDS. BOKATES.  359 


BORACITE. 

Isometric ;  tetrahedral.  Cleavage :  octahedral,  in  traces.  Cubic  faces 
sometimes  striated  parallel  to  alternate  pairs  of  edges,  as  in  pyrite. 

H.  =  7,  in  crystals  ;  4*5,  massive.  G.  =  2*974,  Haidinger.  Lustre  vitre- 
ons,  inclining  to  adamantine.  Color  white,  inclining 
to  gray,  yellow,  and  green.  Streak  white.  Sub- 
transparent — translucent.  Fracture  conchoidal,  un- 
even. Pyroelectric,  and  polar  along  the  four  octa- 
hedral axes. 

Comp.— Mg7B16Cl2OSo  =  2Mg3B8O15+MgCl2  =  Boron  trioxide 
62-57,  magnesia  31 '28,  chlorine  7  "93  =  101 '78. 

Pyr.,  etc. — The  massive  variety  gives  water  in  the  closed  tube. 
B.B.  both  varieties  fuse  at  2  with  intumescence  to  a  white  crys- 
talline  pearl,' coloring  the  flame  green;  heated  after- moistening 

with  cobalt  solution  assumes  a  deep  pink  color.  Mixed  with  copper  oxide  and  heated  on  char- 
coal colors  the  flame  deep  azure-blue  (copper  chloride).  Soluble  in  hydrochloric  acid.  Alters 
very  slowly  on  exposure,  owing  to  the  magnesium  chloride  present,  which  takes  up  water. 

Obs. — Observed  in  beds  of  anhydrite,  gypsum,  or  salt.  In  crystals  at  Kalkberg  and  Schild- 
stein  in  Liineberg,  Hanover ;  at  Segeberg,  near  Kiel,  in  Holstein  ;  at  Luneville,  La  Meurthe, 
France  ;  massive  and  crystallized  ao  Stassfurt,  Prussia. 


BORAX.     Tinkal  of  India. 

Monoclinic.  C=  7-3°  25',  /A  I  =87°,  0  A  24  =  132°  49' ;  c  :  I  :  d  = 
0-4906  :  0-9095  :  1.  Cleavage:  *'-*' perfect;  /less  so;  i-lin  traces. 

H.=2-2-5.  G.  =  1'716.  Lustre  vitreous — resinous;  sometimes  earthy. 
Color  white ;  sometimes  grayish,  bluish,  or  greenish.  Streak  white. 
Translucent — opaque.  Fracture  conchoidal.  Rather  brittle.  Taste  sweet- 
ish-alkaline, feeble. 

Comp — Na2B4O7+10aq=2(NaB02  +  HB02)-t-9aq=Boron  trioxide  36 '6,  soda  16'2,  water 
47-2 

Pyr.,  etc. — B.B.  puffs  up,  and  afterwards  fuses  to  a  transparent  globule,  called  the  glass  of 
borax.  Soluble  in  water,  yielding  a  faintly  alkaline  solution.  Boiling  water  dissolves  double 
its  weight  of  this  salt. 

Obs. — Borax  was  originally  brought  from  a  salt  lake  in  Thibet.  It  is  announced  by  Dr.  J. 
A.  Veatch  as  existing  in  the  waters  of  the  sea  along  the  California  coast,  and  in  those  of 
many  of  the  mineral  springs  of  California.  Occurs  in  the  mud  of  Borax  Lake,  near  Clear 
Lake,  Cal.  Also  found  in  Peru  ;  at  Halberstadt  in  Transylvania ;  in  Ceylon.  It  occurs  in 
solution  in  the  mineral  springs  of  Charnbly,  St.  Ours,  etc., Canada  East.  The  waters  of  Borax 
Lake,  California,  contain,  according  to  Gr.  E.  Moore,  535 '08  grains  of  crystallized  borax  to  the 
gallon. 

ULEXITE.     Boronatrocalcite.     Natronborocalcite. 

In  rounded  masses,  loose  in  texture,  consisting  of  fine  fibres,  which  are 
acicular  or  capillary  crystals. 

II.  =  1.     G.=1'65,  N.  Scotia,  How.     Lustre  silky  within.     Color  white. 

Tasteless. 

Comp.— NaCaB209+5aq=:Boron  trioxide  49'7,  lime  15'9,  soda  8'8,  water  25 '6=100. 
Pyr.,  etc — Yields  water.     B.B.  fuses  at  1  with  intumescence  to  a  clear  blebby  glass,  color 


360  DESCRIPTIVE   MINERALOGY. 

ing  the  flame  deep  yellow.  Moistened  with  sulphuric  acid  the  color  of  the  flame  is  moment- 
arily changed  to  deep  green.  Not  soluble  in  cold  water,  and  but  little  so  in  hot ;  the  solution 
alkaline  in  its  reactions. 

Obs. — Occurs  in  the  dry  plains  of  Iquique,  Southern  Peru ;  in  the  province  of  Tarapaca 
(where  it  is  called  lisa),  in  whitish  rounded  masses,  from  a  hazelnut  to  a  potato  in  size,  which 
consist  of  interwoven  fibres  of  the  ulexite,  with  pickeringite,  glauberite,  halite,  gypsum,  and 
other  imparities;  on  the  West  Africa  coast;  in  Nova  Scotia,  at  Windsor,  Brookville,  and 
Newport  (H.  How),  filling  narrow  cavities,  or  constituting  distinct  nodules  or  mammillated 
masses  imbedded  in  white  gypsum,  and  associated  at  Windsor  with  glauber  salt,  the  lustre 
internally  silky  and  the  color  very  white  ;  in  Nevada,  in  the  salt  marsh  of  the  Columbus 
Mining  District,  forming  layers  2-5  in.  thick  alternating  with  layers  of  salt,  and  in  balls  3-4 
in.  through  in  the  salt. 

BECHILITE.  (Borocalcite). — An  incrustation  at  the  Tuscany  lagoons.  Composition  CaB4O7 
+  4aq.  Also  similar  from  South  America.  LARDERELLITE,  LAGONITE,  rare  borates  from  the 
Tuscan  lagoons. 

PRICEITE  (Sittimari). — Compact,  chalky.  Color  milk-white.  Composition  CasB8O15  +  6aq. 
This  requires  :  Boron  trioxide  49  '8,  lime  29  '9,  water  20  '3  =  100.  Occurs  in  layers  between  a  bed 
of  slate  above  and  one  of  steatite  below.  Near  Chetko,  Curry  Co. ,  Oregon. 

HOWLITE,  Silicoborocalcite. — A  hydrous  calcium  borate  (like  bechilite),  with  one-sixth  of 
a  silicate  analogous  to  danburite.  Near  Brookville,  and  elsewhere  in  Hants  Co. ,  Nova  Scotia, 
in  nodules  imbedded  in  anhydrite  or  gypsum  ;  these  nodules  sometimes  made  up  of  pearly 
crystalline  scales.  WINKWORTHITE.  In  imbedded  crystalline  nodules  from  Winkworth,  N.  S. 
In  composition  between  selenite  and  howlite ;  a  mixture  (?). 

CRYPTOMORPHITE. — Near  ulexite  in  composition.  In  microscopic  rhombic  tables.  Nova 
Scotia. 

LtJNEBURGiTE. — A  phospho-borate  of  magnesium.  Flattened  masses  in  gypsiferous  marl 
at  Liineburg. 


WARWICKITE. 

Monoclinic.  Il\I  =91°  20',  DesCl.  Usual  in  rhombic  prisms  with 
obtuse  edges  truncated,  and  the  acute  bevelled,  summits  generally  rounded  ; 
surfaces  of  larger  crystals  not  polished.  Cleavage :  macrodiagonal  per- 
fect, affording  a  surface  with  vertical  strise  and  traces  of  oblique  cross 
cleavage. 

H.=3-4.  Gr.= 3-19-3-43.  Lustre  of  cleavage  surface  submetallic-pearly 
to  subvitreous ;  often  nearly  dull.  Color  dark  hair-brown  to  dull  black, 
sometimes  a  copper-red  tinge  on  cleavage  surface.  Streak  bluish-black. 
Fracture  uneven.  Brittle. 


Comp Essentially  a  borotitanate  of  magnesium  and  iron.  Analysis,  Smith,  B2O3  27 '80, 

Ti02  23-82,  FeO3  7  "02,  MgO  36 '80,  SiOa  1-00,  A103  2'21=98;65. 

Pyr.,  etc. — Yields  water.  B.B.  infusible,  but  becomes  lighter  in  water ;  moistened  with 
sulphuric  acid  gives  a  pale  green  color  to  the  flame.  With  salt  of  phosphorus  in  O.F.  a  clear 
bead,  yellow  while  hot  and  colorless  on  cooling;  in  R.F.  on  charcoal  with  tin  a  violet  color 
(titanium).  With  soda  a  slight  manganese  reaction.  Decomposed  by  sulphuric  acid  ;  the 
product,  treated  with  alcohol  and  ignited,  gives  a  green  flame,  and  boiled  with  hydrochloric 
acid  and  metallic  tin  gives  on  evaporation  a  violet-colored  solution. 

Obs.— Occurs  in  granular  limestone  2^  m.  S.  W.  of  Edenville,  N.  Y.,  with  spinel,  chondro- 
dite,  serpentine,  etc.  Crystals  usually  small  and  slender ;  sometimes  over  2  in.  long  and  |  in. 
broad. 


OXYGEN  COMPOUNDS TUNGSTATES,  MOLYBDATES,  ETC. 


361 


5.   TUNGSTATES,   MOLYBDATES,   CIIKOMATES. 


WOLFRAMITE. 

Monoclinic.  C  =  89°  22',  /A  7  =  100°  37',  i-i  l\-%4  =  118°  6',  i-i  A  +$-i 
=  117°  6',  14 A  1-1  =  98°  6',  DesOloizeaux.  Cleavage:  -/-i  perfect,  i-i 
imperfect.  Twins :  planes  of  twinning  i-i  (f.  692),  |~i,  and  rarely  -J4. 
Also  irregular  lamellar;  coarse  divergent  columnar;  massive  granular,  the 
particles  strongly  coherent. 

692  693 


H.  — 5-5-5.  G.  =  7'l-7'55.  Lustre  submetallic.  Color  dark  grayish  or 
brownish-black.  Streak  dark  reddish-brown  to  black.  Opaque.  Sometimes 
weak  magnetic. 

Var. — The  most  important  varieties  depend  on  the  proportions  of  the  iron  and  manganese. 
Those  rich  in  manganese  have  Gr.  =7  '19-7  '54,  but  generally  below  7*25,  and  the  streak  is 
mostly  black.  Those  rich  in  iron  have  G.  =7 '2-7 '54,  and  a  dark  reddish-brown  streak,  and 
they  are  sometimes  feebly  attractable  by  the  magnet. 

Comp — (Fe,Mn)WO,,  Fe  :  Mn=2  :  3,  mostly;  also  4  :  1  and  2  :  1,  3  :  1,  5  :  1,  etc.  The 
ratio  2  :  3  corresponds  to  :  Tungsten  trioxide  76'47,  iron  protoxide  9 '49,  manganese  protoxide 
14-04  =  100. 

Pyr.,  etc. — B.B.  fuses  easily  (F. =2*5-3)  to  a.  globule,  which  has  a  crystalline  surface  and 
is  magnetic.  With  salt  of  phosphorus  gives  a  clear  reddish-yellow  glass  while  hot,  which  is 
paler  on  cooling ;  in  R.  F.  becomes  dark  red  ;  on  charcoal  with  tin,  if  not  too  saturated,  the 
bead  assumes  on  cooling  a  green  color,  which  continued  treatment  in  R.F.  changes  to  reddish 
yellow.  With  soda  and  nitre  on  platinum  foil  fuses  to  a  bluish-green  manganate.  Decom- 
posed by  aqua  regia  with  separation  of  tungsten  trioxide  as  a  yellow  powder,  which  when 
treated  B.B.  reacts  as  under  tungstite  (p.  262).  Wolfram  is  sufficiently  decomposed  by  con- 
centrated sulphuric  acid,  or  even  hydrochloric  acid,  to  give  a  colorless  solution,  which,  treated 
with  metallic  zinc,  becomes  intensely  blue,  but  soon  bleaches  on  dilution. 

Diff. — Characterized  by  its  high  specific  gravity  and  pyrognostics. 

Obs. — Wolfram  is  often  associated  with  tin  ores  ;  also  in  quartz,  with  native  bismuth,  scheel- 
ite,  pyrite,  galenite,  blende,  etc.  ;  and  in  trachyte,  as  at  Felso  Banya,  in  Transylvania.  It 
occurs  at  Schlackenwald  ;  Schneeberg ;  Freiberg ;  Ehrenfriedersdorf ;  Zinnwald,  and  Nert- 
schinsk  ;  at  Chanteloup,  near  Limoges,  and  at  Meymac,  Correze,  in  France  ;  near  Redruth 
and  elsewhere  in  Cornwall ;  in  Cumberland.  Also  in  S.  America,  at  Oruro  in  Bolivia. 

In  the  U.  States,  occurs  at  Lane's  mine,  Monroe,  Conn. ;  at  Trumbull,  Conn.  ;  on  Camdage 
farm,  near  Blue  Hill  Bay,  Me.  ;  at  the  Flowe  mine,  Mecklenburg  Co.,  N.  C.  ;  in  Missouri, 
near  Mine  la  Motte,  and  in  St.  Francis  Co. ;  at  Mammoth  mining  district,  Nevada. 

HUBNERITE. — A  manganese  wolframite,  Mn  WO  4= Tungsten  trioxide  76  9,  manganese  prot- 
oxide 23  -1 = 100.  Mammoth  dist. ,  Nevada. 

MEGABASITE.  — A  manganese  tungstate,  with  a  little  iron.     Schlackenwald, 


362 


DESCRIPTIVE   MINERALOGY. 


SCHEELITE. 

Tetragonal ;  hemihedral.  O  A  \4  =  123°  3' ;  c  =  1-5369.  Cleavage  :  1 
most  distinct,  \-i  interrupted,  O  traces.  Twins: 
twinning-plane  I\  also  i-i:  Crystals  usually  octahe- 
dral in  form.  Also  reniform  with  columnar  struc- 
ture ;  and  massive  granular. 

H.— 4-5-5.  Gr.  =  5-9-6-076.  Lustre  vitreous,  in- 
clining to  adamantine.  Color  white,  yellowish-white, 
pale  yellow,  brownish,  greenish,  reddish ;  sometimes 
almost  orange-yellow.  Streak  white.  Transparent 
— translucent.  Fracture  uneven.  Brittle. 

Comp.— CaWO4  =  Tungsten  trioxide  80 '6,  lime  19-4=100.  A 
variety  from  Coquimbo,  Chili,  contained  6 '2  p.  c.  vanadium  pent- 
oxide  ;  another  from  Traversella  contained  didymium. 

Pyr.,  etc. — B.B.  in  the  forceps  fuses  at  5  to  a  semi-transparent 
glass.  Soluble  with  borax  to  a  transparent  glass,  which  after- 
ward becomes  opaque  and  crystalline.  With  salt  of  phosphorus 

Schlackenwalc  forms  a  glass,  colorless  in  outer  flame,  in  inner  green  when  hot 

and  fine  blue  cold ;  varieties  containing  iron  require  to  be  treated 
on  charcoal  with  tin  before  the  blue  color  appears.     In  hydro 
chloric  or  nitric  acid  decomposed,  leaving  a  yellow  powder  soluble  in  ammonia. 
Diff. — Remarkable  among  non-metallic  minerals  for  its  high  specific  gravity. 
Obs. — Usually  associated  with  crystalline  rocks,  and  commonly  found  in  connection  with 
tin  ore,  topaz,  fluorite,  apatite,  molybdenite,  wolframite,  in  quartz.     Occurs  at  Schlacken- 
wald   and  Zinnwald  in  Bohemia;  in  the  Riesengebirge  ;  at  Caldbeck  Fell,  near  Keswick; 
Neudorf  in  the  Harz  ;  Ehrenfriedersdorf ;  Posing  in  Hungary  ;  Traversella  in  Piedmont,  etc. 
Llamuco,  near  Chuapa  in  Chili.     In  the  U.  S.,  at  Lane's  mine,  Monroe,  and  Huntington, 
Conn. ;  at  Chesterfield,  Mass. ;  in  the  Mammoth  mining  district,  Nevada  ;  at  Bangle  mine,  in 
Cabarras  Co.,  N.  C. ;  and  Flowe  mine.  Mecklenburg  Co. 

CUPHOSCIIEELITE. — A  scheelite  containing  about  6  p.  c.  copper  oxide.     Color  bright  green. 
La  Paz,  Lower  California.     Llamuco,  near  Santiago,  Chili. 

CUPROTUNGSTITE.— A  copper  tungstate,   Cu2WO5+aq.      Amorphous.      Color  yellowish- 
green.     With  cuproscheelite  at  the  copper  mines  of  Llamuco,  Chili. 

STOLZITE. — Pb WO 4  =  Tungsten  trioxide  51,  lead  oxide  49  =  100.     Tetragonal.     Zinnwald  ; 
Bleiberg;  Coquimbo,  Chili. 


WULFENITE.     Gelbbleierz,  Germ. 

Tetragonal.     Sometimes   hemihedral.     OM-i=  122°    26' ;    c  =  1'574. 
695  696  697 


Przibram.  Phenixville. 

In  modified  square  tables  and  sometimes  very  thia  octahedrons.     Cleavage 


OXYGEN   COMPOUNDS. TUNGSTATES,    MOLYBDATES,    ETC. 


363 


1  very  smooth ;  O  and  J-  much  less  distinct.  Also  granulariy  massive, 
coarse  or  fine,  firmly  cohesive.  Often  hemihedral  in  the  octagonal  prisms, 
producing  thus  tables  like  f.  696,  and  octahedral  forms  having  the  prisma- 
tic planes  similarly  oblique. 

II.  =  2-75-3.  G.  =  6-03-7'OL  Lustre  resinous  or  adamantine.  Color 
wax-yellow,  passing  into  orange-yellow;  also  siskin-  and  olive-green,  yel- 
lowish-gray, grayish-white,  brown ;  also  orange  to  bright  red.  Streak 
white.  Subtransparent — subtranslucent.  Fracture  subconchoidal.  Brittle. 

Var. — \.  Ordinary.  Color  yellow.  2.  Vanadiferous.  Color  orange  to  bright  red,  a  variety 
occurring  at  Phenixville,  Pa. 

Comp. — PbMO4;=  Molybdenum  trioxide  38 '5,  lead  oxide  61 '5— 100.  Some  varieties  con- 
tain chromium. 

Pyr.,  etc. — B.B.  decrepitates  and  fuses  below  2  ;  with  borax  in  O.F.  gives  a  colorless  glass, 
in  R.F.  it  becomes  opaque  black  or  dirty  green  with  black  flocks.  With  salt  of  phosphorus 
in  O.F.  gives  a  yellowish-green  glass,  which  in  R.F.  becomes  dark  green.  With  soda  on  char- 
coal yields  metallic  lead.  Decomposed  on  evaporation  with  hydrochloric  acid,  with  the 
formation  of  lead  chloride  and  molybdic  oxide  ;  on  moistening  the  residue  with  water  and 
adding  metallic  zinc,  it  gives  an  intense  blue  color,  which  does  not  fade  on  dilution  of  the 
liquid. 

Obs. — This  species  occurs  in  veins  with  other  ores  of  lead.  Found  at  Bleiberg,  etc.,  in 
Carinthia  ;  at  Retzbanya ;  at  Przibram  ;  Schneeberg  and  Johanngeorgenstadt ;  at  Moldawa ; 
in  the  Kirghis  Steppes  in  Russia  ;  at  Badenweiler  in  Baden  ;  in  the  gold  sands  of  Rio  Chico 
in  Antioquia,  Columbia,  S.  A. ;  Wheatley's  mine,  near  Phenixville,  Pa.;  at  the  Comstock  lode 
in  Nevada.  In  fine  specimens  from  the  Empire  mine,  Lucin  District,  Box  Elder  County, 
Utah  ;  at  Empire  mine,  Inyo  Co.,  Cal.  ;  in  the  Weaver  dist.,  Arizona. 

EOSITE  (Schrauf). — In  minute  tetragonal  octahedrons.  Color  deep-red.  Probably  a  vana- 
dio-molybdate  of  lead.  Leadhills,  Scotland. 

ACHREMATITE. — An  arsenio-molybdate  of  lead.  Analysis,  As,05  18 '25,  MoO3  5 '01,  Cl 
215,  Pb  6'28,  PbO  68 -31  =  100-00.  Compact;  structure  indistinctly  crystalline.  H.=3-4. 
G.  =5 '965,  6 '178  (powder).  Color  liver-brown,  translucent;  in  minute  grains  transparent  and 
color  yellow.  Brittle.  Guanacere,  State  of  Chihuahua,  Mexico.  (Mallet,  J.  Ch.  Soc.,  II., 
iii.,  1141.) 


CROCOITE.     Crocoisite.     Rothbleierz,  Germ. 


Monoclinic.     G=  77°  27',  /A  /  =  93°  42',  O  A  14  =  138°  10' ;  c  :  I  :  d 
=  0-95507  :  1/0414  :  1,  Dauber.     Cleavage  :  /toler- 
ably distinct ;   O  and  i-i  less  so.     Surface  /streaked 
longitudinally  ;  the  faces   mostly  smooth  and  shin- 
ing.    Also  imperfectly  columnar  and  granular. 

H.  =  2'5-3.  G.  — 5-9-6-1.  Lustre  adamantine — 
vitreous.  Color  various  shades  of  bright  hyacinth- 
red.  Streak  orange-yellow.  Translucent.  Sectile. 

Comp. — PbCrO4=Lead  oxide  68 '9,  chromium  trioxide  31 '1  = 
100. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  blackens,  but  re- 
covers its  original  color  on  cooling.  B.B.  fuses  at  1'5,  and  on 
charcoal  is  reduced  to  metallic  lead  with  deflagration,  leaving  a 
residue  of  chromic  oxide,  and  giving  a  lead  coating.  With  salt 
of  phosphorus  gives  an  emerald-green  bead  in  both  flames.  Fused 
with  potassium  bisulphate  in  the  platinum  spoon  forms  a  dark  Urals.  Brazil. 

violet  mass,  which  on  solidifying  becomes  reddish,  and  when 

cold  greenish-white,  thus  differing  from  vanadinite,  which  on  similar  treatment   gives  a 
yellow  mass  (Plattner). 


3C4  DESCRIPTIVE   MINERALOGY. 

Obs. — First  found  at  Beresof  in  Siberia  ;  at  Mursinsk  and  near  Nischne  Tagilsk  in  the 
Ural;  in  Brazil;  atRetzbanya;  Moldawa ;  on  Luzon,  one  of  the  Philippines. 


PHCENICOCHROITE.     Melanochroite. 

Orthorliombic  (?).  Crystals  usually  tabular,  and  reticularly  interwoven. 
Cleavage  in  one  direction  perfect.  Also  massive. 

H.=3-3'5.  G.=5'75.  Lustre  resinous  or  adamantine,  glimmering. 
Color  between  cochineal-  and  hyacinth-red ;  becomes  lemon-yellow  on 
exposure.  Streak  brick-red.  Stibtranslucent — opaque. 

Comp. — PbsCrOy— 2PbCr04+PbO= Chromium  trioxide  23 '0,  lead  oxide  77'0=100. 

Pyr.,  etc.— B.  B.  on  charcoal  fuses  readily  to  a  dark  mass,  which  is  crystalline  when  cold. 
In  R.F.  on  charcoal  gives  a  coating  of  lead  oxide,  with  globules  of  lead  and  a  residue  of 
chromic  oxide.  Gives  the  reaction  of  chrome  with  fluxes. 

Obs. — Occurs  in  limestone  at  Beresof  in  the  Ural,  with  crocoite,  vauquelinite,  pyromorphite, 
and  galenite. 


VAUQUELINITE. 

Monoclinic.  Crystals  usually  minute,  irregularly  aggregated.  Also 
reniforrn  or  botryoidal,  and  granular ;  amorphous. 

H.  =  2'5-3.  G.  =  585-5'78.  Lustre  adamantine  to  resinous,  often  faint. 
Color  green  to  brown,  apple-green,  siskin-green,  olive-green,  ochre-brown, 
liver-brown;  sometimes  pearly  black.  Streak  greenish  or  brownish.  Faintly 
translucent — opaque.  Fracture  uneven.  Rather  brittle. 

Comp.— Pb2CuCr,O9=2RCrO4+RO.  R=Pb  :  Cu=2  :  1.  The  formula  requires:  Chro- 
mium trioxide  21  6,  lead  oxide  61 '5,  copper  oxide  10'9  — 100. 

Pyr.,  etc. — B.B.  on  charcoal  slightly  intumesces  and  fuses  to  a  gray  submetallic  globule, 
yielding  at  the  same  time  small  globules  of  metal.  With  borax  or  salt  of  phosphorus  affords 
a  green  transparent  glass  in  the  outer  flame,  which  in  the  inner  after  cooling  is  red  to  black, 
according  to  the  amount  of  mineral  in  the  assay ;  the  red  color  is  more  distinct  with  tin. 
Partly  soluble  in  nitric  acid. 

Obs.— Occurs  with  crocoite  at  Beresof  in  Siberia,  generally  in  mammillated  or  amorphous 
masses,  or  thin  crusts  ;  also  at  Pont  Gibaud  in  the  Puy  de  Dome  ;  and  with  the  crocoite  of 
Brazil.  In  the  U.  States  it  has  been  found  at  the  lead  mine  near  Sing  Sing,  in  green  and 
brownish-green  mamrnillary  concretions,  and  also  nearly  pulverulent ;  and  at  the  Pequa  lead 
mine  in  Lancaster  Co.,  Pa.,  in  minute  crystals  and  radiated  aggregations  on  quartz  and 
galenite,  of  a  siskin-  to  apple-green  color,  with  cerussite. 

LAXMANNITE  (pttosphockromite}. — Near  vauquelinite,  but  held  to  be  a  phospho-chromate. 
Beresof, 


OXYGEN   COMPOUNDS. — SULPHATES. 


365 


6.  SULPHATES. 


ANHYDROUS  SULPHATES. 


Barite  Group. 


BARITE.     Barytes.     Heavy  Spar.     Schwerspath,  Germ. 

Orthorhombic.     /A  7=  101°  40',  O  A 14  =  121°  50' ;  c:l>:a  =  1-6107 


700 


Cheshire. 


:  1-2276  :  1.  O  A 1  =  115°  42' ;  J4  A  £4,  top,  = 
102°  ir  ;  14  A  14,  top,  =  74°  36  Crystals  usu- 
ally tabular,  as  in  figures ;  sometimes  prismatic 
in  the  direction  of  the  different  axes.  Cleavage  : 
basal  rather  perfect ;  I  somewhat  less  so;  i-l  imperfect.  Also  in  globular 
forms,  fibrous  or  lamellar,  crested  ;  coarsely  laminated,  laminae  convergent 
and  often  curved  ;  also  granular ;  colors  sometimes  banded,  as  in  stalagmite. 
H.  =  2*5-3-5.  G.  =  4'3— 4-72.  Lustre  vitreous,  inclining  to  resinous; 
sometimes  pearly.  Streak  white.  Color  white;  also  inclining  to  yellow, 

§ray,  blue,  red,  or  brown,  dark  brown.     Transparent  to  translucent — opaque, 
ometimes  fetid,  when  rubbed.     Optic-axial  plane  brachy diagonal. 

Comp. — BaSO4  =  Sulphur  trioxide  34 '3,  baryta  65 '7= 100.  Strontium  and  sometimes  cal- 
cium replace  part  of  the  barium  ;  also  silica,  clay,  bituminous  or  carbonaceous  substances 
are  often  present  as  impurities. 

Pyr.,  etc. — B.B.  decrepitates  and  fuses  at  3,  coloring  the  flame  yellowish-green ;  the  fused 
mass  reacts  alkaline  with  test  paper.  On  charcoal  reduced  to  a  sulphide.  With  soda  gives 
at  first  a  clear  pearl,  but  on  continued  blowing  yields  a  hepatic  mass,  which  spreads  out  and 
soaks  into  the  coal.  If  a  portion  of  this  mass  be  removed,  placed  on  a  clean  silver  surface, 
and  moistened,  it  gives  a  black  spot  of  silver  sulphide.  Should  the  barite  contain  calcium 
sulphate,  this  will  not  be  absorbed  by  the  coal  when  treated  in  powder  with  soda.  Insoluble 
in  acids. 

Diff. — Distinguishing  characters :  high  specific  gravity,  higher  than  celestite  or  aragonite  ; 
cleavage  ;  insolubility  ;  green  coloration  of  the  blowpipe  flame. 

Obs. — Occurs  commonly  in  connection  with  beds  or  veins  of  metallic  ores,  as  part  of  the 
gangue  of  the  ore.  It  is  met  with  in  secondary  limestone,  sometimes  forming  distinct  veins, 
and  often  in  crystals  along  with  calcite  and  celestite.  At  Dufton,  in  Westmoreland.  Eng- 


366 


DESCRIPTIVE   MINERALOGY. 


land;  in  Cornwall,  near  Liskeard,  etc.,  in  Cumberland  and  Lancashire,  in  Derbyshire,  Staf- 
fordshire, etc.;  in  Scotland,  in  Argyleshire,  at  Strontian.  Some  of  the  most  important 
European  localities  are  at  Felsobanya  and  Kremnitz,  at  Freiberg,  Marienberg,  Clausthal 
Przibram.  and  at  Roya  and  Roure  in  Auvergne 

In  the  U.    " 
Lawrence  Co.; 
Co.;  near  Lexingtoi 

end  of  I.  Royale,  L.  Superior,  and  on  Spar  Id. ,  N.  shore.  In  Canada,  at  Landsdown.  In 
fine  crystals  near  Fort  Wallace,  New  Mexico. 

The  white  varieties  of  barite  are  ground  up  and  employed  as  a  white  paint,  either  alone  or 
mixed  with  white  lead. 


CELESTITE. 

Orthorhombic,  /A  I—  104°  2'  (103°  30/-104°  30'),  O  A  14  =  121° 
19  J' ;  c\l;a  =  1-6432  :  1-2807  :  1.  O  A 1  =  115°  38',  O  A  \4  =  127°  56', 
1  A  1,  ^mac.,  =  112°  35',  1  A  1,  brach..  =  89°  26'.  Cleavage  :  0  perfect ; 
/  distinct ;  i-l  less  distinct.  Also  fibrous  and  radiated  ;  sometimes  globu- 
lar; occasionally  granular. 


702 


703 


L.  Erie. 


H.  =  3— 3'5.  G.  =  3*92-3*975.  Lustre  vitreous,  sometimes  inclining  to 
pearly.  Streak  white.  Color  white,  often  faint  bluish,  and  sometimes  red- 
dish. Transparent — subtranslucent.  Fracture  imperfectly  conchoidal— 
•uneven.  Very  brittle.  Trichroism  sometimes  very  distinct. 

Comp.— SrSO4  =  Sulphur  trioxide  43'6,  strontia  56 '4=100.  Wittstein  finds  that  the  blue 
color  of  the  celestite  of  Jena  is  due  to  a  trace  of  a  phosphate  of  iron. 

Pyr.,  eto. — B.B.  frequently  decrepitates,  fuses  at  3  to  a  white  pearl,  coloring  the  flame 
strontia-red ;  the  fused  mass  reacts  alkaline.  On  charcoal  fuses,  and  in  R.F.  is  converted 
into  a  difficultly  fusible  hepatic  mass ;  this  treated  with  hydrochloric  acid  and  alcohol  gives 
an  intensely  red  flame.  With  soda  on  charcoal  reacts  like  barite.  Insoluble  in  acids. 

Diff. — Does  not  effervesce  with  acids  like  the  carbonates  ;  specific  gravity  lower  than  that 
of  barite  ;  colors  the  blowpipe  flame  red. 

Obs. — Celestite  is  usually  associated  with  limestone  or  sandstone.  Occurs  also  in  beds  of 
gypsum,  rock  salt,  and  clay  ;  and  with  sulphur  in  some  volcanic  regions.  Found  in  Sicily,  at 
Girgenti  and  elsewhere  ;  at  Bex  in  Switzerland,  and  Conil  in  Spain ;  at  Dornburg,  near  Jena ; 
in  the  department  of  the  Garonne,  France  ;  in  the  Tyrol ;  Retzbanya  ;  in  rock  salt,  at  Ischl, 
Austria.  Found  in  the  Trenton  limestone  about  Lake  Huron,  particularly  on  Strontian 
Island,  and  at  Kingston  in  Canada ;  Chaumont  Bay,  Scoharie,  and  Lockport,  N.  Y.  ;  also 
the  Rossie  lead  mine  ;  at  Bell's  Mills,  Blair  Co. ,  Penn. 

Named  from  ccelestis,  celestial,  in  allusion  to  the  faint  shade  of  blue  often  presented  by  the 
mineral. 

BARYTOCELBSTITE. — Celestite  containing  barium  sulphate  26  p.  c.  (Griiner),  20*4  p.  c. 
(Turner).  l-£  A  1-2=74°  54£',  H  A  -H=100J  35',  on  crystals  from  Imfeld  in  the  Binnenthal 
(Neminar).  Drummond  L,  Lake  Erie;  Norton,  Hanover. 


OXYGEN   COMPOUNDS. SULPHATES,   ETC.  367 


ANHYDRITE. 

Orthorhombic.     /A  7=  100°  30',  O  A  14  =  127°  19' ;  c  :  I :  <*  =  1-3122 
:  1-2024  :  1.    1-i A  14,  top,  =  85°.   Cleavage:  ?-i  very  per- 
fect ;  i4  also  perfect ;   0  somewhat  less  so.     Also  fibrous, 
lamellar,    granular,    and    sometimes    impalpable.       The 
lamellar  and  columnar  varieties  often  curved  or  contorted. 
H. =3-3-5.    G.=2-899-2-985.    Lustre:  i-l  and  i-l  some- 
what pearly ;    O  vitreous ;   in  massive  varieties,   vitreous 
inclining  to  pearly.      Color  white,  sometimes  a  grayish, 
bluish,  or  reddish  tinge;  also  brick-red.     Streak  grayish- 
[S^ — 1 — z;p|     white.     Fracture  uneven ;  of  finely  lamellar  and  fibrous 
c  [V    1       ^fj     varieties,  splintery.     Optic-axial  plane  parallel  to  i-i,  or 
Stassfurt.         plane  of  most  perfect  cleavage ;  bisectrix  normal  to  O ; 
Grailich. 

Var.— (a)  Crystallized  ;  cleavable  in  its  three  rectangular  directions,  (b)  fibrous ;  either 
parallel,  or  radiated,  or  plumose,  (c)  Fine  granular,  (d)  Scaly  granular.  Vulpiuite\&  a  scaly 
granular  kind  from  Vulpino  in  Lombardy  ;  it  is  cut  and  polished  for  ornamental  purposes.  It 
does  not  ordinarily  contain  more  silica  than  common  anhydrite.  A  kind  in  contorted  concre- 
tionary forms  is  the  tripestone  (GekrosHlein). 

Comp.— CaSo4-  Sulphur  trioxide  58 '8,  lime  41  "2=100. 

Pyr.,  etc.— B.B.  fuses  at  3,  coloring  the  flame  reddish-yellow,  and  yielding  an  enamel-like 
bead  which  reacts  alkaline.  On  charcoal  in  R.F.  reduced  to  a  sulphide  ;  with  soda  does  not 
fuse  to  a  clear  globule,  and  is  not  absorbed  by  the  coal  like  barite  ;  it  is,  however,  decomposed, 
and  yields  a  mass  which  blackens  silver  ;  with  fluorite  fuses  to  a  clear  pearl,  which  is 
enamel-white  on  cooling,  and  by  long  blowing  swells  up  and  becomes  infusible.  Soluble  in 
hydrochloric  acid. 

Diff. — Characterized  by  its  cleavage  in  three  rectangular  directions ;  harder  than  gypsum  ; 
does  not  effervesce  with  acids  like  the  carbonates. 

Obs. — Occurs  in  rocks  of  various  ages,  especially  in  limestone  strata,  and  often  the  same 
that  contain  ordinary  gypsum,  and  also  very  commonly  in  beds  of  rock  salt.  Occurs  near 
Hall  in  Tyrol ;  at  Sulz  on  the  Neckar,  in  Wiirtemberg  ;  Bleiberg  in  Carinthia ;  Liineberg, 
Hanover ;  Kapnik  in  Hungary ;  Ischl ;  Aussee  in  Styria ;  Berchtesgaden ;  Stassfurt,  in  fine 
crystals.  In  the  U.  States,  at  Lockport,  N.  Y.  In  Nova  Scotia. 

ANGLE  SITE.    Bleivitriol,  Germ. 

Orthorhombic.  7  A  7=  103°  43J-',  O  A  l-l  =  121°  20J',  Kokscharof; 
c:b:d=  1-64223  :  1-273634  :  1.  O  A  l-i  =  127°  48' ;  O  A  1  =  115°  354'-  ; 
14  A  l-#,  top,  =  75°  35^'.  Crystals  sometimes  tabular  ;  often  oblong  pris- 
matic, and  elongated  in  the  direction  of  either  of  the  axes  (as  seen  in  the 
figures).  Cleavage:  7,  O,  but  interrupted.  The  planes  7  and  i-1  often 
vertically  striated,  and  -J4  horizontally.  Also  massive,  granular,  or  hardly 
so.  Sometimes  stalactitic. 

H.  =  2'75-3.  G.  =  6-12-6-39.  Lustre  highly  adamantine  in  some  speci- 
mens, in  others  inclining  to  resinous  and  vitreous.  Color  white,  tinged 
yellow,  gray,  green,  and  sometimes  blue.  Streak  uncolored.  Transparent 
— opaque.  Fracture  conchoidal.  Very  brittle. 

Comp.— PbSO4- Sulphur  trioxide  26  "4,  lead  oxide  73  "6  =  100. 

Pyr.j  etc. — B.B.  decrepitates,  fuses  in  the  flame  of  a  candle  (F.=l*5).  On  charcoal  in  O. 
F.  fuses  to  a  clear  pearl,  which  on  cooling  becomes  milk-white  ;  in  R.F.  is  reduced  with  effer- 
vescence to  metallic  lead.  With  soda  on  charcoal  in  R.F.  gives  metallic  lead,  and  the  soda 
is  absorbed  by  the  coal ;  when  the  surface  of  the  coal  is  removed  and  placed  on  bright  silvei 
and  moistened  with  water  it  tarnishes  the  metal  black.  Difficultly  soluble  in  nitric  acid. 


368 


DESCRIPTIVE    MINERALOGY. 


Diff. — Does  not  effervesce  with  acid  like  cerussite  (lead  carbonate) ;  distinguished  by  blow- 
pipe tests  from  other  resembling  species. 


705 


Siegen. 


Anglesea. 


Obs. — This  ore  of  lead  was  first  observed  by  Monnet  as  a  result  of  the  decomposition  of 
galenite,  and  it  is  often  found  in  its  cavities.  Occurs  in  crystals  at  Leadhills  ;  at  Pary's  mine 
in  Anglesea  ;  also  at  Melanoweth  in  Cornwall ;  in  Derbyshire  and  in  Cumberland  :  Clausthal, 
Zillerfeld,  and  Giepenbach  in  the  Harz ;  near  Siegen  in  Prussia ;  Schapbach  in  the  Black 
Forest ;  in  Sardinia ;  massive  in  Siberia,  Andalusia,  Alston  Moor  in  Cumberland  ;  in  Aus- 
tralia. In  the  U.  S.,  in  large  crystals  at  Wheatley's  mine,  Phenixville,  Pa. ;  in  Missouri  lead 
mines  ;  at  the  lead  mines  of  Southampton,  Mass.  ;  at  Rossie,  N.  Y.  ;  at  the  Walton  gold  mine, 
Louisa  Co.,  Va.  Compact  in  Arizona,  and  Cerro  Gordo,  Cal. 

DREELITE. — Rhombohedral.  H.=3'5.  Gr.=3'2-3'4.  Color  white.  Composition  given  as 
CaSO4-f  3BaSO^.  Occurs  in  small  crystals  at  Beaujeau,  France;  Badenweiler,  Baden. 

DOLEROPHANITE  (Sccicchi). — Cu2S05.  In  minute  crystals.  Monoclinic.  Color  brown. 
Vesuvius. 

HYDROCYANITE  (ScaccM). — Anhydrous  copper  sulphate,  CuSO4.  Color  sky-blue.  Very 
soluble.  Vesuvius. 

APHTHITALITE,  Arcanite. — K2 SO 4= Potash  54-1,  sulphuric  acid  45 '9=100.     Vesuvius. 

THENAKDITE. — Sodium  sulphate,  Na2SO4.     Spain;  Vesuvius. 


LEADHILLITE. 


Orthorhombic.  /A  7=  103°  16',  0  A  14  =  120  °10' ;  c  :  I  :  a  =  1-7205 
:  1*2632  :  1.  Hemihedral  in  /and  some  other  planes  ;  hence  monoclinic  in 
aspect,  or  rhombohedral  when  in  compound  crystals.  Cleavage :  i-%  very 
perfect ;  i-l  in  traces.  Twins,  f .  712,  consisting  of  three  crystals ;  twimring- 
plane,  I-i  (see  f.  298,  p.  97) ;  also  parallel  with  I. 


OXYGEN   COMPOUNDS. — SULPHATES. 


369 


H. = 2-5.  G.  =  6'26-6'44.  Lustre  of  i-l  pearly,  other  parts  resinous,  some- 
what adamantine.  Color  white, 

passing    into    yellow,    green,  711  712 

or  gray.  Streak  un colored. 
Transparent  —  translucent. 
Conchoid al  fracture  scarcely 
observable.  .Rather  sectile. 

Comp. — Formerly  accepted  for- 
mula, PbSO4+3PbCO3=Lead  sul- 
phate 27'45,  lead  carbonate  72-55  — 
100.  Recent  investigations  by  Las- 
peyres  (J.  pr.,  Ch.  II.,  v.,  470;  vii., 
127;  xiii.,  870),  and  Hintze  (Pogg. 
Ann.,  clii.,  156),  though  not  entirely 
accordant,  give  different  results,  both 
show  the  presence  of  some  water.  Laspeyres  writes  the  formula  empirically,  Pbi8C9S505i  + 
5HaO,  and  Hintze,  Pb7C4S2021+2H2O.  Analyses:  1.  Laspeyres;  2,  Hintze: 
SO3  C02  PbO  H20 

1.  8-14  8-08  81-91  1-87=100,  Laspeyres. 

2.  817  918  80-80  2  -00= 100  '15,  Hintze. 

Pyr.,  etc, — B.B.  intumesces,  fuses  at  1*5,  and  turns  yellow  ;  but  white  on  cooling.  Easily 
reduced  on  charcoal.  With  soda  affords  the  reaction  for  sulphuric  acid.  Effervesces  briskly 
in  nitric  acid,  and  leaves  white  lead  sulphate  undissolved. 

Obs, — This  ore  has  been  found  at  Leadhills  with  other  ores  of  lead  ;  also  in  crystals  at  Red 
Gill,  Cumberland,  and  near  Taunton  in  Somersetshire  ;  at  Iglesias,  Sardinia  (maxite). 

SUSANNITE. — Composition  as  for  leadhillite,  but  form  rhombohedral.  Leadhills;  Nert- 
schinsk,  Siberia. 

CONNELLITE. — Hexagonal.  In  slender  needle-like  blue  crystals.  Contains  copper  sulphate 
and  copper  chloride.  Exact  composition  uncertain.  Cornwall. 

CALEDONITE.—  Monoclinic  (Schrauf).  H.  =2-5-3.  G.  =6'4.  Color  bluish-green.  R2SO5 
+  aq  (Flight),  with  R=Pb  :  Cu=7  :  3,  or  5PbSO4+3H,CuO2+2H.PbO2.  This  requires  : 
Sulphuric  trioxide  19 •!,  lead  oxide  65 '2,  copper  oxide  11*4,  water  4'3=100.  Leadhills,  Scot- 
land ;  Red  Gills  ;  Retzbanya  ;  Mine  la  Motte,  Missouri. 

LANAHKITE. — Monoclinic.  H.  =2-2*5.  G.  =6-3-6 -4.  Color  pale  yellow,  or  greenish- 
white.  Transparent.  Composition  as  formerly  accepted,  PbSO4+PbCO3.  New  analyses  by 
Flight,  and  by  Pisani,  show  the  absence  of  both  carbon  dioxide  and  water  ;  composition 
accordingly  Pb2S05=PbS04+PbO,  which  requires  :  Lead  sulphate  57-6.  lead  oxide  42'4=100. 
Leadhills ;  Siberia,  etc. 


GLAUBERITE. 

Monoclinic.      C  =  68°  16/,   /A  /  =83°  20', 
=  0-8454  :  0-8267  :  1.     Cleavage  :  O  perfect. 

H.=2-5-3. 
pale  yellow  or 
Fracture  conchoidal  ;  brittle. 


O  A 14  =  136°  30'  •   c:b 


.  =  2-64:-2'85.     Lustre   vitreous.      Color 
ray;  sometimes  brick-red.    Streak  white. 
Taste  slightly  saline. 


Comp.—  ]S"a2CaS2Ofe=Sulphur  trioxide  57-6,  lime  20'1,  soda  22  3  = 
100. 

Pyr.,  etc.—  B.B.  decrepitates,  turns  white,  and  fuses  at  1'5  to  a 
white  enamel,  coloring  the  flame  intensely  yellow.  On  charcoal  fuses 
in  O.  F.  to  a  clear  bead  ;  in  R.  F.  a  portion  is  absorbed  by  the  charcoal, 
leaving  an  infusibe  hepatic  residue.  With  soda  on  charcoal  gives  the 
reaction  for  sulphur.  Soluble  in  hydrochloric  acid.  In  water  it  loses 
its  transparency,  is  partially  dissolved,  leaving  a  residue  of  calcium 
sulphate,  and  in  a  large  excess  this  is  completely  dissolved.  On  long 
exposure  absorbs  moisture  and  falls  to  pieces. 

Obs.  —  In  crystals  in  rock  salt  at  Villa  Rubia  in  New  Castile  ;  also  at 
Aussee  in  Upper  Austria  ;  in  Bavaria  ;  at  the  salt  mines  of  Vic  in  France  ; 
and  at  Borax  Lake,  California;  Province  of  Tarapaca,  Peru. 
24 


3TO 


DESCRIPTIVE   MINERALOGY. 


HYDROUS    SULPHATES. 


MIRABILITB.      Glauber  Salt. 

Monoclinic.  C=  72°  15',  /A  7=  86°  31',  O  A 14  =  130°  19';  c  :  I  :  d 
=  1-1089  :  0-8962  :  1.  Cleavage  :  i-i  perfect.  Usually  in  efflorescent 
crusts. 

H.  =  1-5-2.  G.  =  1*481.  Lustre  vitreous.  Color  white.  Transparent- 
opaque.  Taste  cool,  then  feebly  saline  and  bitter. 


Very 
Falls 


Comp.— Na2SO4  +  10aq= Sulphur  trioxide  24 '8,  soda  19  -3,  water  55-9=100. 

Pyr.,  etc. — In  the  closed  tube  much  water  ;  gives  an  intense  yellow  to  the  flame, 
soluble  in  water ;  the  solution  gives  with  barium  salts  the  reaction  for  sulphuric  acid, 
to  powder  on  exposure  to  the  air,  and  becomes  anhydrous. 

Obs. — Occurs  afc'Ischl  and  Hallstadt ;  also  in  Hungary  ;  Switzerland  ;  Italy ;  at  G-uipnzcoa 
in  Spain,  etc.  ;  at  Kailua  on  Hawaii ;  at  Windsor,  Nova  Scotia ;  also  near  Sweetwater  liiver, 
Rocky  Mountains. 

MASCAGNITE,  BOUSSINGAULTITE  (cerbolite),  LECONTITE,  and  GDANOVULITE  are  hydrous 
sulphates  containing  ammonium. 


GYPSUM. 

Monoclinic.  C  •=  66°  14',  if  the  vertical  prism  7  (see  f.  716)  correspond 
to  the  cleavage  prism  (second  cleavage),  and  the  basal  plane  O  to  the 
direction  of  the  third  cleavage.  7A/=138°  28',  14  A  14  =  128°  31'; 
c  :  b  :  d  =  0-9  :  2-4135  :  1.  O  A  1  =  125°  35',  O  A  24=145°  41',  1  A  1  = 
143°  42',  24  A  24= 111°  42'. 


715 


Cleavage :  (1)  £4,  or  clinodiagonal,  eminent,  affording  easily  smooth  pol- 
ished folia ;  (2)  7,  imperfect,  fibrous,  and  often  apparent  in  internal  rifts  or 
linings,  making  with  O  (or  the  edge  24/24)  the  angles  66°  14',  and  113° 
46',  corresponding  to  the  obliquity  of  the  fundamental  prism ;  (3)  O,  or 
basal,  imperfect,  but  affording  a  nearly  smooth  surface.  Twins  :  1.  Twin- 
ning-plane  O  common  (f.  717) ;  also  14,  or  edge  1/1.  Simple  crystals  often 
with  warped  as  well  as  curved  surfaces.  Also  foliated  massive;  lamellar 
stellate ;  often  granular  massive ;  and  sometimes  nearly  impalpable. 


OXYGEN   COMPOUNDS. SULPHATES.  371 

H.  =  1*5-2.  G.  =  2-314-2-328,  when  pure  crystals.  Lustre  of  i-l  pearly 
and  shining,  other  faces  subvitreons.  Massive  varieties  often  glistening, 
sometimes  dull  earthy.  Color  usually  white ;  sometimes  gray,  flesh-red, 
honey-yellow,  ochre-yellow,  blue  ;  impure  varieties  often  black,  brown,  red. 
or  reddish-brown.  Streak  white.  Transparent — opaque. 

Var. — 1 .  Crystallized,  or  Selenite ;  either  in  distinct  crystals  or  in  broad  folia,  the  folia 
sometimes  a  yard  across  and  transparent  throughout.  2.  Fibrous;  coarse  or  fine,  (a)  Satin 
spar,  when  fine-fibrous  a  variety  which  has  the  pearly  opalescence  of  moonstone  ;  (b)  plumose, 
when  radiatedly  arranged.  3.  Massive;  Alabaster,  a  fine-grained  variety,  either  white  or 
delicately  shaded ;  scaly -granular  ;  earthy  or  rock-gypsum,  a  dull-colored  rock,  often  impure 
with  clay  or  calcium  carbonate,  and  sometimes  with  anhydrite. 

Comp— CaSO4  +  2aq= Sulphur  trioxide  46 '5,  lime  32 'G,  water  20 '9  =  100. 

Pyr.,  etc. — In  the  closed  tube  gives  off  water  and  becomes  opaque.  Fuses  at  2 '5-3,  color- 
ing the  flame  reddish-yellow.  For  other  reactions,  see  ANHYDRITE,  p.  367.  Ignited  at  a 
temperature  not  exceeding  260°  C.,  it  again  combines  with  watar  when  moistened,  and 
becomes  firmly  solid.  Soluble  in  hydrochloric  acid,  and  also  in  400  to  500  parts  of  water. 

Diff. — Characterized  by  its  softness ;  it  does  not  effervesce  nor  gelatinize  with  acids. 
Some  varieties  resemble  heulandite,  stilbite,  talc,  etc.;  and  in  its  fibrous  forms  it  is  like  some 
calcite. 

Obs. — Gypsum  often  forms  extensive  beds  in  connection  with  various  stratified  rocks,  espe- 
cially limestone,  and  marlytes  or  clay  beds.  It  occurs  occasionally  in  crystalline  rocks.  It  is 
also  a  product  of  volcanoes  ;  produced  by  the  decomposition  of  pyrite  when  lime  is  present ; 
and  often  about  sulphur  springs  ;  also  deposited  on  the  evaporation  of  sea-water  and  brines, 
in  which  it  exists  in  solution. 

Fine  specimens  are  found  in  the  salt  mines  of  Bex  in  Switzerland  ;  at  Hall  in  the  Tyrol ; 
in  the  sulphur  mines  of  Sicily  ;  in  the  gypsum  formation  near  O<<ana  in  Spain ;  in  the  clay  of 
Shotover  Hill,  near  Oxford  ;  at  Montmartre,  near  Paris.  A  noted  locality  of  alabaster  occurs 
at  Castelino,  35  m.  from  Leghorn.  In  the  U.  S.  this  species  occurs  in  extensive  beds  in 
N.  York,  Ohio,  Illinois,  Virginia,  Tennessee,  and  Arkansas ;  it  is  usually  associated  with  salt 
springs.  Also  in  Nova  Scotia,  Peru,  etc.  It  is  characteristic  of  the  so-called  triassic,  or  red 
beds,  of  the  Rocky  Mountain  region ;  also  of  the  Cretaceous  in  the  west,  particularly  of  the 
clays  of  the  Fort  Pierre  group,  in  which  it  occurs  in  the  form  of  transparent  plates. 

Handsome  selenite  and  snowy  gypsum  occur  in  N.  York,  near  Lockport ;  also  near  Camil- 
lus.  Onondaga  Co.  In  Maryland,  on  the  St.  Mary's,  in  clay.  In  Ohio,  large  transparent 
crystals  have  been  found  at  Poland  and  Canfield,  Trumbull  Co.  In  Tenn.,  selenite  and  ala- 
baster in  Davidson  Co.  In  Kentucky,  in  Mammoth  Cave,  in  the  form  of  rosettes,  etc.  In 
N.  Scotia,  in  Sussex,  King's  Co.,  large  crystals,  often  containing  much  symmetrically  dis- 
seminated sand  (Marsh). 

Plaster  of  Paris  (or  gypsum  which  has  been  heated  and  ground  up)  is  used  for  making 
moulds,  taking  casts  of  statues,  medals,  etc.  ;  for  producing  a  hard  finish  on  walls;  also  in 
the  manufacture  of  artificial  marble,  as  the  scagliola  tables  of  Leghorn,  and  in  the  glazing  of 
porcelain. 


POLYHALITE. 

Monoclinic  (?).  A  prism  of  115°,  with  acute  edges  truncated.  Usually  in 
compact  fibrous  masses. 

11.  =  2-5-3.  Gr.  =  2-7689.  Lustre  resinous  or  slightly  pearly.  Streak 
red.  Color  flesh-  or  brick-red,  sometimes  yellowish.  Translucent — opaque. 
Taste  bitter  and  astringent,  but  very  weak. 

Comp.— 2RSO4+aq,  where  R=Ca  :  Mg  :  K2  in  the  ratio  2:1:1;  that  is,  K,MgCa.S4OiB 
+2aq  — Calcium  sulphate  45'2,  magnesium  sulphate  19'9,  potassium  sulphate  28'9,  water 
6-0=100. 

Pyr.,  etc, — In  the  closed  tube  gives  water.  B.B  fuses  at  1'5,  colors  the  flame  yellow.  On 
charcoal  fuses  to  a  reddish  globule,  which  in  R.F.  becomes  whitef  and  on  cooling  has  a  saline 
hepatic  taste  ;  with  soda  like  glauberite.  With  fluor  does  not  give  a  clear  bead.  Partially 
soluble  in  water,  leaving  a  residue  of  calcium  sulphate,  which  dissolves  in  a  large  amount  of 
water. 


372  DESCRIPTIVE  MINERALOGY. 

Obs. — Occurs  at  the  mines  of  Ischl,  Ebensee,  Aussee,  Hallstatt,  and  Hallein  in  Austria, 
with  common  salt,  gypsum,  and  anhydrite  ;  at  Berchtesgaden  in  Bavaria  ;  at  Vic  in  Lorraine. 

The  name  Poly  halite  is  derived  from  TT<J\V$,  many,  and  aA.s,  salt,  in  allusion  to  the  number 
of  salts  in  the  constitution  of  the  mineral. 

SYNGENITE,  v.  Zepharovich  ;  Kaluszite,  Rumpf. — Near  polyhalite.  Composition  RSO4  + 
aq,  with  R^Ca  :  K2  =  l  :  1,  that  is,  K2CaS.2O8+aq=rPotassium  sulphate  53'1,  calcium  sul- 
phate 41  "4,  water  5  -5  =  100.  Monoclinic.  Occurs  in  small  tabular  crystals  in  cavities  in  halite 
at  Kalusz,  East  G-alicia. 

KIESEIUTE.—  MgSO4+aq=Sulphur  trioxide  58-0,  magnesia  28'0,  water  13'0=100.  Stass- 
fort. 

PICROMERITE  is  K  MgS2O8+6aq:=Sulphur  trioxide  39'8,  magnesia  9'9,  potash  23*4,  water 
26 -9  =  100.  Vesuvius;  Stassfurt. 

BLOEDITE. — Composition  jNa2MgS2O8  +  4aq=Sulphur  trioxide  47 '9,  magnesia  12'0,  soda 
18-6,  water  21 '5= 100.  Salt  mines  of  Ischl ;  also  in  the  Andes.  SIMONYITE  (Tscherma/e)  is 
identical. 

LCEWEITE.—  2N"a2MgS208+5aq= Sulphur  trioxide  52'1,  magnesia  13'0,  soda  20  2,  water 
14-7=100.  From  Ischl. 

EPSOMITE.    Epsom  Salt.     Bittersalz,  Germ. 

Orthorhombic,  and  generally  hemihedral  in  the  octahedral  modifications. 
/A  7=90°  34',  O  A  1-^  =  150°  2';  c:  I  \&  =  0-5766  :  1-01  :  1.  1-2  A  1-2, 
basal,  =  59°  27',  14 A 14,  basal,  —  59°  56'.  Cleavage:  brachydiagonal, 
perfect.  Also  in  botryoidal  masses  and  delicately  fibrous  crusts. 

H.  =  2-25.  G.  — 1-751;  1-685,  artificial  salt.  Lustre  vitreous — earthy. 
Streak  and  color  white.  Transparent — translucent.  Taste  bitter  and  saline. 

Comp. — MgSO4+7aq,  when  pure  =  Sulphur  trioxide  32'5,  magnesia  16 '3,  water  51 -2=100." 

Pyr.,  etc. — Liquifies  in  its  water  of  crystallization.  Gives  much  water  in  the  closed  tube 
at  a  high  temperature;  the  water  is  acid.  B.B.  on  charcoal  fuses  at  first,  and  finally  yield? 
an  infusible  alkaline  mass,  which,  with  cobalt  solution,  gives  a  pink  color  on  ignition.  Very 
soluble  in  water,  and  has  a  very  bitter  taste. 

Obs. — Common  in  mineral  waters,  and  as  a  delicate  fibrous  or  capillary  efflorescence  on 
rocks,  in  the  galleries  of  mines,  and  elsewhere.  In  the  former  state  it  exists  at  Epsom,  Eng- 
land, and  at  Sedlitz  and  Saidschutz  in  Bohemia.  At  Idria  in  Carniola  it  occurs  in  silky  fibres, 
and  is  hence  called  Jiairsalt  by  the  workmen.  Also  obtained  at  the  gypsum  quarries  of  Morit- 
martre,  near  Paris  ;  in  Aragon  and  Catalonia  in  Spain  ;  in  Chili ;  found  at  Vesuvius,  etc. 

The  floors  of  the  limestone  caves  of  Kentucky,  Tennessee,  and  Indiana,  are  in  many 
instances  covered  with  epsomite,  in  minute  crystals,  mingled  with  the  earth.  In  the  Mam- 
moth Cave,  Ky.,  it  adheres  to  the  roof  in  loose  masses  like  snowballs. 

FAUSEHITE. — A  hydrous  manganese-magnesium  sulphate.     Hungary. 


Copperas  Group. 
CHALOANTHITE.    Blue  Vitriol.     Kupfervitriol,  Germ. 

Triclinic.  O  A  7=109°  32',  O  Mr  =  127°  40',  /A/'  =  123°  10',  6>Al 
=125°  38',  0/\i-l  =  l20°  50',  0A*-*  =  103°  27'.  Cleavage:  /imper- 
fect, /'  very  imperfect.  Occurs  also  amorphous,  stalactitic,  reniform. 

H.  =  2-5.  G. =2-213.  Lustre  vitreous.  Color  Berlin-blue  to  sky-blue, 
of  different  shades  ;  sometimes  a  little  greenish.  Streak  uncolored.  Sub- 
transparent — translucent.  Taste  metallic  and  nauseous.  Somewhat  brittle. 

Comp. — CuS04  4  5aq= Sulphur  trioxide  32'1,  copper  oxide  31*8,  water  36-1  =  100. 

Pyr.,  etc. — In  the  closed  tube  yields  water,  and  at  a  higher  temperature  sulphuric  acid. 
B.B.  with  soda  on  charcoal  yields  metallic  copper.  With  the  fluxes  reacts  for  copper.  Solu- 
ble in  water ;  a  drop  of  the  solution  placed  on  a  surface  of  iron  coats  it  with  metallic  copper. 

Obs, — BJ,ue  vitriol  is  found  in  waters  issuing  from  mines,  and  in  connection  with  rocks  con- 
taining chalcopyrite,  by  the  alteration  of  which  it  is  formed.  Some  of  its  foreign  localities 


OXYGEN   COMPOUNDS. SULPHATES.  373 

are  the  Rammelsberg  mine,  near  Goslar,  in  the  Harz  ;  Fahlun  in  Sweden ;  at  Parys  mine, 
Anglesey ;  at  various  mines  in  Co.  of  Wicklow  ;  Rio  Tinto  mine,  Spain.  Found  at  the 
Hiwassee  copper  mine,  and  other  mines,  in  Polk  Co. ,  Tennessee  ;  at  the  Canton  mine,  Georgia ; 
at  Copiapo,  Chili,  with  stypticite. 

When  purified  it  is  employed  in  dyeing  operations,  and  in  the  printing  of  cotton  and  linen, 
and  for  various  other  purposes  in  the  arts.  It  is  manufactured  mostly  from  old  sheathing, 
copper  trimmings,  and  refinery  scales. 

Other  vitriols  are  : — MELANTERIT  E,  iron  vitriol ;  PISANITE,  iron-copper  vitriol ;  GOSLAR- 
ITE,  zinc  vitriol ;  BIEBEKITE,  cobalt  vitriol ;  MORENOSITE,  nickel  vitriol ;  CDPROMAGNESITE, 
copper-magnesium  vitriol  (Vesuvius).  These  are  all  alike  in  containing  7  molecules  of  water 
of  crystallization. 

ALUNOGEN  (Haarsalz,  Germ.). — AlS3Oi2+18aq=Sulphurtrioxide36'0,  aluminalo-4,  water 
48-0  =  100.  Taste  like  that  of  alum.  Vesuvius;  Konigsberg,  Hungary. 

COQUIMBITE. — FeS3Oi2+9aq=Sulphur  trioxide  42-7,  iron  sesquioxide  28-5,  water  28'8= 
100.  Coquimbo.  Chili. 

ETTRINGITE  (Lehmann).—  Analysis,  S03  16'64,  A1O3  7-76,  CaO  27 '27,  H.O  45'82.  In  hexa- 
gonal needle-like  crystals  from  the  lava  at  Ettringen,  Laacher  See. 


Alum  and  Halotrichite  Groups. 

Here  belong :  TSCHERMIGITE,  ammonium  alum.  KALINITE,  potassium  alum,  or  common 
alum.  MENDOZITE,  sodium  alum.  PICKERINGITE,  magnesium  alum.  APJOHNITE,  man- 
ganese alum.  BOSJEMANNITE,  mangano-magnesium  alum.  HALOTRICHITE,  iron  alum. 
Also  RCEMEIUTE,  and  VOLTAITE. 


COPIAPITB. 

Hexagonal  (?).  Loose  aggregation  of  crystalline  scales,  or  granular  massive, 
the  scales  rhombic  or  hexagonal  tables.  Cleavage :  basal,  perfect.  In- 
crusting. 

IT.=i'5.  G.=2'14,  Borcher.  Lustre  pearly.  Color  sulphur-yellow, 
citron-yellow.  Translucent. 

Comp. — Fe2S502i+18aq,  Rose;  5FeS3Oi2  +  H6Fe06=Sulphur  trioxide  41 '9,  iron  sesqui- 
oxide 33'5,  water  24 '5  =  100. 

Pyr.,  etc — Yields  water,  and  at  a  higher  temperature  sulphuric  acid.  On  charcoal  be- 
comes magnetic,  and  with  soda  affords  the  reaction  for  sulphur.  With  the  fluxes  reactions 
for  iron.  In  water  insoluble. 

Obs. — Common  as  a  result  of  the  decomposition  of  pyrite  at  the  Rammelsberg  mine,  near 
Goslar  in  the  Harz,  and  elsewhere. 

This  species  is  the  yellow  copperas  long  called  misy,  and  it  might  well  bear  now  the  name 
Misylite. 

RAIMONDITE. — Composition  Fe2S3Oi6+7aq.  FIBROFERRITE  (stypticite).— Composition 
FeS,O9  +  10aq. 

BOTRYOGEN  is  red  iron  vitriol,  exact  composition  uncertain.  Fahlun,  Sweden.  BARTHO- 
LOMITE,  West  Indies,  is  related. 

IIILEITE. — Fe2S3Oi2  +  12aq.  Occurs  as  a  yellow  efflorescence  on  graphite  from  Mugrau, 
Bohemia  (Schrauf). 


ALUMINITE. 


Reniform,  massive ;  impalpable. 

H.=l-2.      G.=1'66.      Lustre   dull,   earthy.      Color  white.      Opaque. 
Fracture  earthy.     Adheres  to  the  tongue ;  meagre  to  the  touch. 


374  DESCRIPTIVE   MINERALOGY. 

Comp — AlS06+9aq=: Sulphur  trioxide  23'2,  alumina  29 '8,  water  47-0=100. 

Pyr.,  etc. — In  the  closed  tube  gives  much  water,  which,  at  a  high  temperature,  becomes 
acid  from  the  evolution  of  sulphurous  and  sulphuric  oxides.  B.B.  infusible.  With  cobalt 
solution  a  fine  blue  color.  With  soda  on  charcoal  a  hepatic  mass.  Soluble  in  acids. 

Obs. — Occurs  in  connection  with  beds  of  clay  in  the  Tertiary  and  Post- tertiary  formations. 
Found  near  Halle ;  at  Newhaven,  Sussex ;  Epernay,  in  Lunel  Vieil,  and  Auteuil,  in  France. 

WEKTHEMANITK.— AlSO6  +  3aq.     G.  =2'80.     Occurs  near  Chachapoyas,  in  Peru. 

ALUNITE,  Alaunstein,  Germ. — Composition  KaAlaS-jOaa  +  Caq-  Rhombohedral.  Also 
massive,  fibrous.  Forms  seams  in  trachyte  and  allied  rocks.  Tolfa,  near  Rome  ;  Tuscany; 
Hungary  ;  Mt.  Dore,  France,  etc. 

LOWIGITE. — Same  composition  as  alunite,  but  contains  3  parts  more  of  water.  Tabrze, 
Silesia. 

LINARITE.     Bleilasur,  Kupferbleispath,  Germ. 

Monoclinic.  C=  77°  27' ;  /A  7,  over  i-i,  =  61°  36',  O  A  14  =  141°  5', 
c:b:d  =  0-48134  :  0-5819  :  1,  Hessenberg.  Twins: 
twinn ing-plane  i-i  common  ;  O  A  O'  =  154°  54'. 
Cleavage  :  i-i  very  perfect ;  O  less  so. 

H.  =  2'5.  G.  =  5.3-5*45.  Lustre  vitreous  or  ada- 
mantine. Color  deep  azure-blue.  Streak  pale*  blue. 
Translucent.  Fracture  conchoidal.  Brittle. 

Comp.— PbCuSO 5  + aq=(Pb,Cu)S04 +H2(Pb,Cu)02  — Sulphur  trioxide  20'0,  lead  oxide  55 -7, 
copper  oxide  19 '8,  water  4*5=100. 

Pyr.,  etc, — In  the  closed  tube  yields  water  and  loses  its  blue  color.  B.B.  on  charcoal  fuses 
easily  to  a  pearl,  and  in  R.F.  is  reduced  to  a  metallic  globule  which  by  continued  treatment 
coats  the  coal  with  lead  oxide,  and  if  fused  boron  trioxide  is  added  yields  a  pure  globule  of 
copper.  With  soda  gives  the  reaction  for  sulphur.  Decomposed  with  nitric  acid,  leaving  a 
white  residue  of  lead  sulphate. 

Obs. — Formerly  found  at  Leadhills.  Occurs  at  Roughten Grill,  Red  Gill,  etc.,  in  Cumber- 
laud  ;  near  Schneeberg,  rare;  in  Dillenburg ;  at  Retzbany  a ;  inNertschinsk;  and  near  Beresof 
in  the  Ural ;  and  supposed  formerly  to  be  found  at  Linares  in  Spain,  whence  the  name. 


BROCHANTITE. 

Monoclinic.  C  =  89°  27i'.  '  1  A  /=  104°  6i',  O  A  14  =  154°  12*'  ;  c  : 
I  :  d  —  0-61983  :  1-28242  :  1.  Schrauf  distinguishes  four  types  of  forms  : 
I.  Brocbantite  from  Retzbanya  (two  varieties),  also  from  Cornwall  and 
Russia,  tri  clinic  ;  II.  Warringtonite  from  Cornwall,  a  third  variety  from 
Retzbanya,  monoclinic  (?)  ;  III.  Brochantite  from  Nischne-Tagilsk,  mono- 
clinic  —  triclinic  ;  IY.  Konigine  from  Russia,  and  a  fourth  variety  from  Retz- 
banya, monoclinic  (or  orthorhombic). 

Also  in  groups  of  acicular  crystals  and  drusy  crusts.  Cleavage  :  i-\  very 
perfect  ;  /  in  traces.  Also  massive  ;  reniform  with  a  columnar  structure. 

H.=3-5-4.  G-.  —  3-78-3-87,  Magnus;  3*9069,  G-.  Rose.  Lustre  vitreous  ; 
a  little  pearly  on  the  cleavage-face.  Color  emerald-green,  blackish-green. 
Streak  paler  green.  Transparent  —  translucent. 


Comp.—  Cu4SO7  +  8H2O=CuS04  +  3H;Cu02=:Sulphur  trioxide  17'71,  copper  oxide  70  '34, 
water  11  '95  =100.  This  formula  belongs  to  type  IV.,  above;  the  warringtonite  corresponds 
more  nearly  to  CuSO44-3H2CuOj-t-H,O,  and  the  existence  of  other  varieties  has  been  also 
assumed. 

Pyr.,  etc.  —  Yields  water,  and  at  a  higher  temperature  sulphuric  acid,  in  the  closed  tube, 
and  becomes  black.  B.B.  fuses,  and  on  charcoal  affords  metallic  copper.  With  soda  give's 
the  reaction  for  sulphuric  acid. 


OXYGEN   COMPOUNDS. — SULPHATES.  375 

Obs. — Occurs  at  Gumeschevsk  and  Nischne-Tagilsk  in  the  Ural ;  the  Konigine  (or  Konigite) 
was  from  Gumeschevsk ;  near  Roughten  Gill,  in  Cumberland  ;  in  Cornwall  (in  part  warring  - 
tonite)  ;  at  Retzbanya  ;  in  Nassau ;  at  Krisuvig  in  Iceland  (krisumgltd) ;  in  Mexico  (brongnar- 
tine) ;  in  Chili,  at  Andacollo  ;  in  Australia. 

Named  after  Brochant  de  Villiers. 

LANGITE. — CuSO4  +  2HiCuOj  +  2aq.  In  crystals  and  concretionary  crusts  of  a  blue  color. 
G.  =  3'5.  Cornwall. 

CYANOTRICIIITE.  Lettsomite.  Kupfersammterz,  Oerm. — In  velvety  druses.  Color  blue. 
Anhydrous  sulphate  of  copper  and  aluminum.  Moldava  in  the  Banat.  WOODWARDITE,  near 
the  above. 

KRONKITE — CuS04-i-Na2S04  +  2aq=Copper  sulphate  47'2,  sodium  sulphate  42 '1,  water 
10-7^100.  In  irregular  crystalline  masses  of  a  coarse  fibrous  structure,  prismatic.  Color 
azure-blue.  Moist  to  the  touch.  Found  in  the  copper  mines  near  Calama,  Bolivia.  (Domeyko.} 

PHILMPITE. — CuS04+FeSiOi2+^aq.  In  irregular  fibrous  masses,  not  prismatic.  Color 
bluo.  In  the  cordilleras  of  Condes,  Santiago,  Chili.  (Domeyko.) 

ENYSITE. — Occurs  in  stalactitic  forms  in  a  cave.  H.=2-2'4.  G.  =1*59.  Color  bluish  - 
green.  B.B.  infusible.  Analysis:  S03  8'12,  A1O3  29-85,  CuO  16'91,  CaO  1'35,  H20  39'42, 
SiO,  3-40,  CO2  1-05—100.  Near  St.  Agnes,  Cornwall.  (Collins,  Min.  Mag.,  1,  p.  14.) 

URANIUM-SULPHATES. — There  are  included  here  jolmnnite,  uranochalcite,  medjidite,  zippeite, 
voglianite,  ur aconite.  These  are  secondary  products  found  with  other  uranium  minerals  at 
Joachimsthal. 


TELLUKATES. 


MONTANITE. 

Incrnsting ;  without  distinct  crystalline  structure. 

Soft  and  earthy.     Lustre    dull    to   waxy.     Color  yellowish   to  white. 
Opaque. 

Comp.— Bi2TeO6  +  2aq= Tellurium  trioxide  26-1,  bismuth  oxide  68'6,  water  5'3=100. 
Pyr.,  etc. — Yields  water  in  a  tube  when  heated.     B.B.  gives  the  reactions  of  bismuth  and 
tellurium.     Soluble  in  dilate  hydrochloric  acid. 

Obs — Incrusts  tetradymite,  at  Highland,  in  Montana  ;  Davidson  Co. ,  N.  0. 


376 


DESCRIPTIVE   MINERALOGY. 


7.  CAKBONATES. 
ANHYDROUS  CARBONATES. 

Calcite  Group. 
CALCITB.    Calc  Spar.    Kalkspath,  Germ. 

Bhombohedral.     E  A  R,   terminal,  =  105°   5', 
0-8543.     Cleavage  :  R  highly  perfect. 

719  720  721  722 

"         '         AA      */. 

J  \\\        U 


ANGLES  OP  RHOMBOHEDRONS. 


Term.  Edge. 
156°    2' 
134°  57' 
105°    5' 


166°  9' 
153°  45' 
135°  23' 


r-f 

2(-2) 
4(-4) 


Term.  Edge. 
95°  28' 
78°  51' 
65°  50' 


129°  2 
116°  52' 
104°  17' 


Edge  X  (f.  724).        Y. 

3r3  138°     5'  159°  24' 

P          128°  15'  146°   10' 

I3          104°  38'  144°  24' 
I6          109°    1' 


ANGLES  OF  SCALENOHEDRONS. 
Z. 

64°  54' 

90°  20'  -f 

132°  58'  -i 


EdgeX. 
130°  37' 


134°  28'      150°  44' 


-22 


107°  38' 
117°  23' 
92°    9' 


Y. 

164°     1' 
145°  15' 


Z. 

67°  41' 
124°  39' 


149°  43'      102°  25' 
153°  16'      135°  19' 


OXYGEN    COMPOUNDS. — CARBONATES. 


377 


Twins:  (1)  Twinning-plane  basal  (or  parallel  to  0).    "(2)  R-,  the  vertical 
axes  of  the  two  forms  nearly  at  right  angles.     (3)  —  2j?.     (4)  —  \R,  the 


vertical  axes  of  the  two  forms  inclined  to  one  another  127°  34/.  (5)  Pris- 
matic plane  ?'-2.  (6)  plane  i  (see  p.  95). 

Also  fibrous,  both  coarse  and  fine;  sometimes  lamellar;  often  granular  ; 
from  coarse  to  impalpable,  arid  compact  to  earthy.  Also  stalactitic,  tube- 
rose, nodular,  and  other  imitative  forms. 

II.  =  2-5-3-5  ;  some  earthy  kinds  (chalk,  etc.)  1.  G.—  2'508-2'778  ;  pure 
crystals,  2'7213-2'7234r,  Beud.  Lustre  vitreous  —  subvitreous  —  earthy.  Color 
white  or  colorless  ;  also  various  pale  shades  of  gray,  red,  green,  blue,  violet, 
yellow  ;  also  brown  and  black  when  impure.  Streak  white  or  grayish. 
Transparent  —  opaque.  Fracture  usually  conchoidal,  but  obtained  with 
difficulty  when  the  specimen  is  crystallized.  Double  refraction  strong. 


729 


Alston-Moor. 


Comp.,  Var.— Calcite  is  calcium  carbonate,  CaC03= Carbon  dioxide  4i,  lime  56  =  100. 
Part  of  the  calcium  is  sometimes  replaced  by  magnesium,  iron,  or  manganese,  more  rarely  by 
strontium,  barium,  zinc,  or  lead. 

The  varieties  are  very  numerous,  and  diverse  in  appearance.  They  depend  mainly  on  the 
following  points  :  (1)  differences  in  crystallization;  (2)  in  structural  condition,  the. extremes 
being  perfect  crystals  and  earthy  massive  forms;  (3)  in  color,  diaphaneity,  odor  on  friction, 
due  to  impurities ;  (4)  in  modes  of  origin. 

1.  Ofystafl&ed.  Crystals  and  crystallized  masses  afford  easily  cleavage  rhombohedrons ;  and 
when  transparent  they  are  called  Iceland  Spar,  and  also  Doubly-i  efracting  Spar  (Doppels- 
path,  Germ.}. 

The  crystals  vary  in  proportions  from  broad  tabular  to  moderately  slender  acicular,  and 
take  a  great  diversity  of  forms.  But  the  extreme  kinds  so  pass  into  one  another  through  those 
that  are  intermediate  that  no  satisfactory  classification  is  possible.  Many  are  stout  or  short 
in  shape  because  normally  so.  But  other  forms  that  are  long  tapering  in  their  full  develop- 


378  DESCRIPTIVE   MINERALOGY. 

ment  occur  short  and  stout  because  abbreviated  by  an  abrupt  termination  in  a  broad  #,  or  an 
obtuse  rhombohedron  (as  -i  or  B),  or  a  low  scalenohedron  (as  £3),  or  a  combination  of  these 
forms  ;  and  thus  the  crystals  having  essentially  the  same  combinations  of  planes  vary  greatly 
in  shape.  The  acute  scalenohedrons  like  f.  724,  are  called  dog-tooth  spar. 

Fontainebleau  limestone.  Crystals  of  the  form  in  f.  719c,  from  Fontainebleau  and  Nemours, 
France,  containing  a  large  amount  of  sand,  some  50  to  63  p.  c.  Similar  sandstone  crys- 
tals occur  at  Sievring,  near  Vienna,  and  elsewhere.  Pseudomorphous  scalenohedrons  of  sand- 
stone, after  calcite,  are  found  near  Heidelberg. 

Satin  Spar;  fine  fibrous,  with  a  silky  lustre.  Resembles  fibrous  gypsum,  which  is  also 
called  satin  spar,  but  is  much  harder  and  effervesces  with  acids.  Argentine  (Schieferspath), 
a  pearly  lamellar  calcite,  the  lamellse  more  or  less  undulating ;  color  white,  grayish,  yellowish, 
or  reddish.  Aphrite,  in  its  harder  and  more  sparry  variety  (Schaumspath)  is  a  foliated  white 
pearly  calcite,  near  argentine  ;  in  its  softer  kinds  (Schaumerde,  Silvery  Chalk,  Ecume  de  Terre 
H.)  it  approaches  chalk,  though  lighter,  pearly  in  lustre,  silvery- white  or  yellowish  in  color, 
soft  and  greasy  to  the  touch,  and  more  or  less  scaly  in  structure. 

2.  Massive  Varieties.  Granular  limestone  (Saccharoidal  limestone,  so  named  because  like  loaf- 
sugar  in  fracture).  The  texture  varies  from  quite  coarse  to  very  fine  granular,  and  the  latter 
passes  by  imperceptible  shades  into  compact  limestone.  The  colors  are  various,  as  white, 
yellow,  reddish,  green,  and  usually  they  are  clouded  and  give  a  handsome  effect  when  the 
material  is  polished.  When  such  limestones  are  fit  for  polishing,  o'r  for  architectural  or  orna- 
mental use,  they  are  called  marbles.  Statuary  marble  is  pure  white,  fine  grained,  and  firm 
in  texture.  Hard  compact  limestone,  varies  from  nearly  pure  white,  through  grayish,  drab, 
buff,  yellowish,  and  reddish  shades,  to  bluish-gray,  dark  brownish-gray,  and  black,  and  is  some- 
times variously  veined.  The  colors  dull,  excepting  ochre-yellow  and  ochre-red  varieties. 
Many  kinds  make  beautiful  marble  when  polished. 

Shell-marble  includes  kinds  consisting  largely  of  fossil  shells.  Ruin-marble  is  a  kind  of  com- 
pact calcareous  marl,  showing,  when  polished,  pictures  of  fortifications,  temples,  etc. ,  in  ruins, 
due  to  infiltration  of  oxide  of  iron.  Lithographic  stone  is  a  very  even  grained  compact  lime- 
stone, usually  of  buff  or  drab  color ;  as  that  of  Solenhofen.  Breccia  marble  is  made  of  frag- 
ments of  limestone  cemented  together,  and  is  often  very  beautiful  when  the  fragments  are  of 
different  colors,  or  are  imbedded  in  a  base  that  contrasts  well.  The  colors  are  very  various. 
Pudding  stone  marble  consists  of  pebbles  or  rounded  stones  cemented.  It  is  often  called, 
improperly,  breccia  marble. 

Hydraulic  limestone  is  an  impure  limestone.  The  varieties  in  the  United  States  contain  20 
to  40  p.  c.  of  magnesia,  and  12  to  30  p.  c.  of  silica  and  alumina. 

Soft  compact  limestone.  Chalk  is  white,  grayish -white,  or  yellowish,  and  soft  enough  to 
leave  a  trace  on  a  board.  The  consolidation  into  a  rock  of  such  softness  may  be  owing  to  the 
fact  that  the  material  is  largely  the  hollow  shells  of  rhizopods.  Calcareous  marl  (Mergel- 
kalk,  Germ. )  is  a  soft  earthy  deposit,  often  hardly  at  all  consolidated,  with  or  without  dis- 
tinct fragments  of  shells  ;  it  generally  contains  much  clay,  and  graduates  into  a  calcareous 
clay. 

Concretionarg  massive.  Oolite  (Rogenstein,  Germ.}  is  a  granular  limestone,  but  its  grains 
are  minute  rounded  concretions,  looking  somewhat  like  the  roe  of  a  fish,  the  name  coming 
from  'uov,  egg.  It  occurs  among  all  the  geological  formations,  from  the  Lower  Silurian  to 
the  most  recent,  and  it  is  now  forming  about  the  coral  reefs  of  Florida.  Pisolite  (Erbsentein, 
Germ.)  consists  of  concretions  as  large  often  as  a  small  pea,  or  even  larger,  the  concretions 
having  usually  a  distinct  concentric  structure.  It  is  formed  in  large  masses  in  the  vicinity  of 
the  Hot  Springs  at  Carlsbad  in  Bohemia. 

Deposited  from  calcareous  springs,  streams,  or  in  caverns,  etc.  (a)  Stalactites  are  the  calcareous 
cylinders  or  cones  that  hang  from  the  roofs  of  limestone  caverns,  and  which  are  formed  from 
the  waters  that  drip  through  the  roof ;  these  waters  hold  some  calcium  bicarbonate  in  solu- 
tion, and  leave  calcium  carbonate  to  form  the  stalactite  when  evaporation  takes  place.  Sta- 
lactites vary  from  transparent  to  nearly  opaque  ;  from  a  granular  crystalline  structure  to  a 
radiating  fibrous ;  from  a  white  color  and  colorless  to  yellowish-gray  and  brown,  (b)  Stalag- 
mite is  the  same  material  covering  the  floors  of  caverns,  it  being  made  from  the  waters  that 
drop  from  the  roofs,  or  from  sources  over  the  bottom  or  sides ;  cones  of  it  sometimes  rise  from 
the  floor  to  meet  the  stalactites  above. 

(c)  Calc-sinter,  Travertine,  Calc  Tufa,     Travertine  ( Confetto  di  Tivoli)  is  of  essentially  the 
same  origin  with  stalagmite,  but  is  distinctively  a  deposit  from  springs  or  rivers,  especially 
where  in  large  deposits,  as  along  the  river  Anio,  at  Tivoli,  near  Rome,  where  the  deposit  is 
scores  of  feet  in  thickness.     It  has  a  very  cavernous  and  irregularly  banded  structure,  owing 
to  its  mode  of  formation. 

(d)  Agaric  mineral;  Rock-milk  (Bergmilch,  Montmilch,  Germ.)  is  a  very  soft,  white  material, 
breaking  easily  in  the  fingers,  deposited  sometimes  in  caverns,  or  about  sources  holding  lime 
in  solution. 


OXYGEN  COMPOUNDS. CARBONATES.  379 

(e)  Rock-meal  (Bergmehl,  G-erm.)  is  white  and  light,  like  cotton,  becoming  a  powder  on  the 
slightest  pressure.  It  is  an  efflorescence,  and  is  common  near  Paris,  especially  at  the  quarries 
of  Nanterre. 

Fyr.,  etc. — In  the  closed  tube  sometimes  decrepitates,  and,  if  containing  metallic  oxides, 
may  change  its  color.  B.B.  infusible,  but  becomes  caustic,  glows,  and  colors  the  flame  red  ; 
after  ignition  the  assay  reacts  alkaline ;  moistened  with  hydrochloric  acid  imparts  the  charac- 
teristic lime  color  to  the  flame.  In  borax  dissolves  with  effervescence,  and  if  saturated, 
yields  on  cooling  an  opaque,  milk-white,  crystalline  bead.  Varieties  containing  metallic 
oxides  color  the  borax  and  salt  of  phosphorus  beads  accordingly.  With  soda  on  platinum  foil 
fuses  to  a  clear  mass ;  on  charcoal  it  at  first  fuses,  but  later  the  soda  is  absorbed  by  the  coal, 
leaving  an  infusible  and  strongly  luminous  residue  of  lime.  In  the  solid  mass  effervesces 
when  moistened  with  hydrochloric  acid,  and  fragments  dissolve  with  brisk  effervescence  even 
in  cold  acid. 

Diff. — Distinguishing  characters  :  perfect  rhombohedral  cleavage ;  softness,  can  be  scratched 
with  a  knife  ;  eifervescence  in  cold  dilute  acid ;  inf usibility.  Less  hard  and  of  lower  specific 
gravity  than  aragonite. 

Obs. — Andreasberg  in  the  Harz  is  one  of  the  best  European  localities  of  crystallized  calcite ; 
there  are  other  localities  in  the  Tyrol,  Styria,  Carintbia,  Hungary,  Saxony,  Hesse  Darmstadt 
(at  Auerbach),  Hesse  Cassel.  Norway,  France,  and  in  England  in  Derbyshire,  Cumberland, 
Cornwall ;  Scotland  ;  in  Iceland. 

In  the  TJ.  States  prominent  localities  are  :  in  N.  York,  in  St.  Lawrence  and  Jefferson  Cos., 
especially  at  the  Rossie  lead  mine  ;  in  Antwerp;  dog-tooth  spar,  in  Niagara  Co.,  near  Lock- 
port  ;  near  Booueville,  Oneida  Co.  ;  at  Anthony's  Nose,  on  the  Hudson  ;  at  Watertown, 
Agaric  mineral]  at  Schoharie,  fine  stalactites  in  many  caverns.  In  Conn.,  at  the  lead  mine, 
Middletown.  In  J¥.  Jersey,  at  Bergen.  In  Virginia,  at  the  celebrated  Wier's  cave,  stalactites 
of  great  beauty;  also  in  the  large  caves  of  Kentucky.  At  the  Lake  Superior  copper  mines, 
splendid  crystals  often  containing  scales  of  native  copper.  At  Warsaw,  Illinois  ;  at  Quincy, 
111.;  at  Hazle  Green,  Wis.  In  Nova  Scotia,  at  Partridge  I. 


DOLOMITE. 


Rhombohedral.  Rf\R  =  lW°  15',  O  A  B  =  136°  8£';  c  =  0-8322. 
E  A  R  varies  between  106°  10'  and  106°  20'.  Cleavage  : 
R  perfect.  Faces  R  often  curved,  and  secondary 
planes  usually  with  horizontal  striae.  Twins  :  similar 
to  f.  733.  Also  in  imitative  shapes;  also  amorphous, 
granular,  coarse  or  fine,  and  grains  often  slightly 
coherent. 

B.=3-5-4:.  G.  =  2-8-2l-9,  true  dolomite.  Lustre  vit- 
reous, inclining  to  pearly  in  some  varieties.  Color  white,  reddish,  or  green- 
ish-white ;  also  rose-red,  green,  brown,  gray,  and  black.  Subtransparent  to 
trans-lucent.  Brittle. 

Comp,,  Var.  —  (Ca,Mg)Cos,  the  ratio  of  Ca  :  Mg  in  normal  or  true  dolomite  is  1  :  l=Cal- 
cium  carbonate  54  '35,  magnesium  carbonate  45  "65.  Some  kinds  included  under  the  name 
have  other  proportions  ;  but  this  may  arise  from  their  being  mixtures  of  dolomite  with  calcite 
or  magnesite.  Iron,  manganese,  and  more  rarely  cobalt  or  zinc  are  sometimes  present. 

The  varieties  are  the  following  : 

Crystallized.  Pearl  spar  includes  rhombohedral  crystallizations  with  curved  faces.  Colum- 
nar or  fibrous.  Granular  constitutes  many  of  the  kinds  of  white  statuary  marble,  and  white 
and  colored  architectural  marbles,  names  of  some  of  which  have  been  mentioned  under  calcite. 

Compact  massive,  like  ordinary  limestone.  Many  of  the  limestone  strata  of  the  globe  are 
here  included,  and  much  hydraulic  limestone,  noticed  under  calcite. 

Ferriferous  :  Brown  spar,  in  part.  Contains  iron,  and  as  the  proportion  increases  it  gradu- 
ates into  ankerite  (q.  v.  ).  The  color  is  white  to  brown,  and  becomes  brownish  on  exposure 
through  oxidation  of  the  iron.  Manganiferoits.  Colorless  to  flesh-red.  R/\It=lQGa  23  ; 
100°  16'.  Cobaltiferous.  Colored  reddish  ;  G.=  2  "921,  Gibbs. 

The  varieties  based  on  variations  in  the  proportions  of  the  carbonates  are  the  following  : 
(a)  Normal  dolomite,  ratio  of  Ca  to  Mg=l  :  1,  (b)  ratio  1-J  :  1=3  :  2  ;  ratio=2  :  1  ;  ratio  3  : 
1  ;  ratio  =5  :  1  ;  ratio  1:3.  The  last  (/)  may  be  dolomitic  magnesite  ;  and  the  others,  from 


380  DESCRIPTIVE   MINERALOGY. 

(£),  dolomitic  calcite,  or  calcite  +  dolomite.  The  manner  in  which  dolomite  is  ofted  mixed 
with  calcite,  forming  its  veins  and  its  fossil  shells  (see  below),  shows  that  this  is  not  improb- 
able. 

Pyr.,  etc. — B.  B.  acts  like  calcite,  but  does  not  give  a  clear  mass  when  fused  with  soda  on 
platinum  foil.  Fragments  thrown  into  cold  acid  are  very  slowly  acted  uoon,  while  in  powdei 
in  warm  acid  fie  mineral  is  readily  dissolved  with  effervescence.  The  ferriferous  dolomites 
become  brown  on  exposure. 

Difif. — Resembles  calcite,  but  generally  to  be  distinguished  in  that  it  does  not  effervesce 
readily  in  the  mass  in  cold  acid. 

Obs, — Massive  dolomite  constitutes  extensive  strata,  called  limestone  strata,  in  various 
regions.  Crystalline  and  compact  varieties  are  often  associated  with  serpentine  and  other 
magnesian  rocks,  and  with  ordinary  limestones.  Some  of  the  prominent  localities  are  at  Salz- 
burg ;  the  Tyrol ;  Schemnitz  in  Hungary ;  Kapnik  in  Transylvania ;  Freiberg  in  Saxony ; 
the  lead  mines  at  Alston  in  Derbyshire,  etc. 

In  the  U.  States,  in  Vermont,  at  Roxbury.  In  Rhode  Island,  at  Smithfield.  In  N.  Jersey, 
at  Hoboken.  In  N.  York,  at  Lockport,  Niagara  Falls,  and  Rochester  ;  also  at  Glenn's  Falls, 
in  Richmond  Co.,  and  at  the  Parish  ore  bed,  St.  Lawrence  Co.;  at  Brewster,  Putnam  Co. 

Named  after  Dolomieu,  who  announced  some  of  the  marked  characteristics  of  the  rock  in 
1791 — its  not  effervescing  with  acids,  while  burning  like  limestone,  and  its  solubility  after 
heating  in  acids. 


ANKERITE. 

Rhombohedral.  R  A  R  —  106°  7',  Zepharovich.  Also  crystalline  mas- 
sive, coarse  or  fine  granular,  and  compact. 

H.  =  3-5-4.  G.  —  2-95-3-1 .  Lustre  vitreous  to  pearly.  Color  white,  gray, 
reddish.  Translucent  to  subtransluceut. 

Comp. — CaC03+FeC03+#(CaMgC2O6).  Here,  according  to  Boricky,  x  may  have  the  values 
i,  1,  t,  |,  £,  2,  3,  4,  5,  10.  The  varieties  having  the  five  higher  values  of  x  he  calls  paran- 
kerite,  while  the  others  are  normal  ankerite.  If  x=l,  the  formula  is  equivalent  to  2CaC03  + 
MgCO3+FeCO3,  and  requires:  Calcium  carbonate  50,  magnesium  carbonate  21,  iron  carbon- 
ate 29  =  100.  Manganese  is  also  sometimes  present. 

Pyr.,  etc. — B.B.  like  dolomite,  but  darkens  in  color,  and  on  charcoal  becomes  black  and 
magnetic ;  with  the  fluxes  reacts  for  iron  and  manganese.  Soluble  with  effervescence  in  the 
acids. 

Obs. — Occurs  with  siderite  at  the  Styrian mines;  in  Bohemia;  Siegen  ;  Schneeberg;  Nova 
Scotia,  etc. 


MAGNESITE. 


Ehombohedral.  K/\R=  107°  29',  Ot\R  =  136°  56'  ;  c  =  0;8095. 
Cleavage:  rhombohedral,  perfect.  Also  massive;  granular,  to  very  com- 
pact. 

H.=3-5-4-5.  G.  =  3-3-OS,  cryst.  ;  2-8,  earthy;  3-3  '2,  when  ferriferous. 
Lustre  vitreous  ;  fibrous  varieties  sometimes  silky.  Color  white,  yellowish 
or  grayish-white,  brown.  Transparent  —  opaque.  Fracture  flat  conchoid  al. 

Var.  —  Ferriferous,  Breunerite  ;  containing  several  p.  c.  of  iron  protoxide;  G.=3-3'2; 
white,  yellowish,  brownish,  rarely  black  and  bituminous;  often  becoming  brown  on  exposure, 
and  hence  called  Brown  Spar. 

Comp.—  Magnesium  carbonate,  MgC03=Carbon  dioxide  52  '4,  magnesia  4?  '6  =  100;  but  iron 
often  replacing  some  magnesium. 

Pyr.,  etc.—  B.  H.  resembles  calcite  and  dolomite,  and  like  the  latter  is  but  slightly  acted 
upon  by  cold  acids  ;  in  powder  is  readily  dissolved  with  effervescence  in  warm  hydrochloric 
acid. 

Obs.—  Found  in  talcose  schist,  serpentine,  and  other  magnesian  rocks  ;  as  veins  in  serpen- 
tine. or  mixed  with  it  so  as  to  form  a  variety  of  verd-antique  marble  (magnesitic  ophiolite  of 


OXYGEN  COMPOUNDS. — CARBONATES.  381 

Hunt) ;  also  in  Canada,  as  a  rock,  more  or  less  pure,  associated  with  steatite,  serpentine,  and 
dolomite. 

Occurs  at  Hrubschiitz  in  Moravia ;  in  Styria,  and  in  the  Tyrol ;  at  Frankenstein  in  Silesia ; 
Snarum,  Norway  ;  Baudissero  and  Castellamonte  in  Piedmont.  In  America,  at  Bolton,  Mass.; 
at  Barehills,  near  Baltimore,  Md.  ;  in  Perm.,  at  West  G-oshen,  Chester  Co.  ;  near  Texas,  Lan- 
caster Co.  ;  California. 

MESITITE  and  PISTOMESITE  come  under  the  general  formula  (Mg,Fe)C03 ;  with  the  former 
Mg  :  Fe=2  :  1  ;  with  the  latter=l  :  1. 

SIDE  RITE.     Spathic  Iron.     Chalybite.  Eisenspath,  Gtrm. 

Khombohedral.     B/\R=WT,  0  A  R  =  136°  37' ;   c  =  0-81715.     The 
faces  often  curved,  as  below.     Cleavage :  rhom- 
bohedral,  perfect.    Twins  :  twinning-plane  —  -£.  735 

Also  in  botryoidal  and  globular  forms,  sub- 
fibrons  within,  occasionally  silky  fibrous.  Often 
cleavable  massive,  with  cleavage  planes  undu- 
lating. Coarse  or  fine  granular. 

IL:=3-5-4:-5.  G.=3-7-3-9.  Lustre  vitreous, 
more  or  less  pearly.  Streak  white.  Color  ash- 
gray,  yellowish-gray,  greenish-gray,  also  brown 
and  brownish-red,  rarely  green  ;  and  sometimes 
white.  Translucent — subtranslucent.  Fracture 
uneven.  Brittle. 

Comp.,  Var. — Iron  carbonate,  FeCO3= Carbon  dioxide  37 '9,  iron  protoxide  62*1.  But  part 
of  the  iron  usually  replaced  by  manganese,  and  often  by  magnesium  or  calcium.  Some 
varieties  contain  8-10  p.  c.  MnO. 

The  principal  varieties  are  the  following  : 

(1)  Ordinary,  (a)  Crystallized,  (b)  Conor etionary = Splier osiderite  ;  in  globular  concretions, 
either  solid  or  concentric  scaly,  with  usually  a  fibrous  structure,  (c}  Granular  to  compact  mas- 
sive, (d)  Oolitic,  like  oolitic  limestone  in  structure.  (e)  Earthy,  or  stony,  impure  from 
mixture  with  clay  or  sand,  constituting  a  large  part  of  the  clay  iron-stone  of  the  coal  forma- 
tion and  other  stratified  deposits  ;  H.  =3  to  7,  the  last  from  the  silica  present ;  G-.  =3'0-3'8, 
or  mostly  3 '15 -3 '05. 

Pyr.,  etc. — In  the  closed  tube  decrepitates,  evolves  carbon  oxide  and  carbon  dioxide, 
blackens  and  becomes  magnetic.  B.B.  blackens  and  fuses  at  4  "5.  With  the  fluxes  reacts  for 
iron,  and  with  soda  and  nitre  on  platinum  foil  generally  gives  a  manganese  reaction.  Only 
slowly  acted  upon  by  cold  acid,  but  dissolves  with  brisk  effervescence  in  hot  hydrochloric  acid. 

DifT. — Specific  gravity  higher  than  that  of  calcite  and  dolomite.  B.B.  becomes  magnetic 
readily. 

Obs. — Siderite  occurs  in  many  of  the  rock  strata,  in  gneiss,  mica  slate,  clay  slate,  and  as 
clay  iron-stone  in  connection  with  the  Coal  formation  and  many  other  stratified  deposits.  It 
is  often  associated  with  metallic  ores.  At  Freiberg  it  occurs  in  silver  mines.  In  Cornwall  it 
accompanies  tin.  It  is  also  found  accompanying  copper  and  iron  pyrites,  galenite,  vitreous 
copper,  etc.  In  New  York,  according  to  Beck,  it  is  almost  always  associated  with  specular 
iron.  In  the  region  in  and  about  Styria  and  Carinthia  this  ore  forms  extensive  tracts  in  gneiss. 
At  Harzgerode  in  the  Harz,  it  occurs  in  fine  crystals ;  also  in  Cornwall,  Alston-Moor,  and 
Devonshire  ;  near  Glasgow  ;  also  at  Mouillar,  Magescote,  etc.,  in  France,  etc. 

In  the  U.  States,  in  Vermont,  at  Plymouth.  In  Mass.,  at  Sterling.  In  Conn.,  at  Roxbury. 
In  N.  York,  at  the  Sterling  ore  bed  in  Antwerp,  Jefferson  Co.  ;  at  the  Rossie  iron  mines,  St. 
Lawrence  Co.  In  N.  Carolina,  at  Fentress  and  Harlem  mines.  The  argillaceous  carbonate, 
in  nodules  and  beds  (clay  iron-stone),  is  abundant  in  the  coal  regions  of  Penn. ,  Ohio,  and  many 
parts  of  the  country. 

RHODOCHROSITE.    Dialogite.    Manganspath,  Germ. 

•Ehombohedral.  E/\R  =  106°  51',  O/\R=  136°  31^ ;  c  =  0-8211. 
Cleavage  :  7?,  perfect.  Also  globular  and  botryoidal,  having  a  columnar 
structure,  sometimes  indistinct.  Also  granular " massive;  occasionally  im- 
palpable ;  incrusting. 


382  DESCRIPTIVE   MINERALOGY. 

JEL  =3-5-4'5.  G.=3-4-3'7.  Lustre  vitreous,  inclining  to  pearly.  Color 
shades  of  rose-red,  yellowish-gray,  fawn-colored,  dark  red,  brown.  Streak 
white.  Translucent — subtranslucent.  Fracture  uneven.  Brittle. 

Comp. — MnCO3=Carbon  dioxide  38 '3,  manganese  protoxide  61 '7;  but  part  of  the  man- 
ganese usually  replaced  by  calcium,  and  often  also  by  magnesium  or  iron  ;  and  sometimes  by 
cobalt. 

Pyr.;  etc. — B.B.  changes  to  gray,  brown,  and  black,  and  decrepitates  strongly,  but  is  in- 
fusible. With  salt  of  phosphorus  and  borax  in  O.F.  gives  an  amethystine-colored  bead  in 
R.F.  becomes  colorless.  With  soda  on  platinum  foil  a  bluish -green  mangsmate.  Dissolves 
with  effervescence  in  warm  hydrochloric  acid.  On  exposure  to  the  air  changes  to  brown,  and 
r-ome  bright  rose-red  varieties  become  paler. 

Obs, — Occurs  commonly  in  veins  along  with  ores  of  silver,  lead,  and  copper,  and  with  other 
ores  of  manganese.  Found  at  Schemuitz  and  Kapnik  in  Hungary  ;  Nagyag  in  Transylvania  ; 
near  Elbingerode  in.  the  Harz  ;  at  Freiberg  in  Saxony. 

Occurs  in  New  Jersey,  at  Mine  Hill,  Franklin  Furnace.  Abundant  at  the  silver  mines  of 
Austin,  Nevada  ;  at  Placentia  Bay,  Newfoundland. 

Named  rJwdoG/irosite  from  {>6$ovt  a  rose,  and  xpc6<ns,  color  ;  and  dialogite,  from  StaAoy^j,  doubt. 


SMITHSONITE.     Calamine  pt.     Galmei  pt.     Zickspath,  Germ. 

Ehombohedral.  72  A  72  =107°  40',  6>  A  72  =  137°  3' ;  c  =  0-8062.  E 
generally  curved  and  rough.  Cleavage  :  72  perfect.  Also  reniform,  botry- 
oidal,  or  stalactitic,  and  in  crystalline  incrustations;  also  granular,  and 
sometimes  impalpable,  occasionally  earthy  and  friable. 

H.  =  5.  Gr. =4—4-4:5.  Lustre  vitreous,  inclining  to  pearly.  Streak  white. 
Color  white,  often  grayish,  greenish,  brownish-white,  sometimes  green 
and  brown.  Subtransparent — translucent.  Fracture  uneven — imperfectly 
conchoidal.  Brittle. 

Comp.,  Var.—ZnCO3= Carbon  dioxide  35 '2,  zinc  oxide  64 '8  =  100;  but  part  of  the  zinc 
often  replaced  by  iron  or  manganese,  and  by  traces  of  calcium  and  magnesium  ;  sometimes 
by  cadmium. 

.  Varieties. — (1)  Ordinary.  («)  Crystallized;  (b)  botryoidal  and  stalactitic,  common;  (c) 
granular  to  compact  massive;  (d)  earthy,  impure,  in  nodular  and  cavernous  masses,  varying 
from  grayish-white  to  dark  gray,  brown,  brownish -red,  brownish-black,  and  often  with  diusy 
surfaces  in  the  cavities  ;  kk  dry-bone  "  of  American  miners. 

Pyr.,  etc, — In  the  closed  tube  loses  carbon  dioxide,  and,  if  pure,  is  yellow  while  hot  and 
colorless  on  cooling.  B.B.  infusible ;  moistened  with  cobalt  solution  and  heated  in  O.F,  gives 
a  green  color  on  cooling.  With  soda  on  charcoal  gives  zinc  vapors,  and  coats  the  coal  yellow 
white  hot,  becoming  white  on  cooling ;  this  coating,  moistened  with  cobalt  solution,  gives  a 
green  color  after  heating  in  O.  F.  Cadmiferous  varieties,  when  treated  with  soda,  give  at 
first  a  deep  yellow  or  brown  coating  before  the  zinc  coating  appears.  With  the  fluxes  some 
varieties  react  for  iron,  copper,  and  manganese.  Soluble  in  hydrochloric  acid  with  efferves- 
cence. 

Diff. — Distinguished  from  oalamine  by  its  effervescence  in  acids. 

Obs. — Smithsonite  is  found  both  in  veins  and  beds,  especially  in  company  with  galeuite 
and  blende  ;  also  with  copper  and  iron  ores.  It  usually  occurs  in  calcareous  rocks,  and  is 
generally  associated  with  calamiue,  and  sometimes  with  limonite.  It  is  often  produced  by 
the  action  of  zinc  sulphate  upon  calcium  or  magnesium  carbonate. 

Found  at  Nertschinsk  in  Siberia  ;  at  Dognatzka  in  Hungary ;  Bleiberg  and  Raibel  in  Carin- 
thia;  Moresnet  in  Belgium.  In  England,  at  Roughten  Gill,  Alston  Moor,  near  Matlock,  in 
the  Mendip  Hills,  and  elsewhere  ;  in  Scotland,  at  Leadhills;  in  Ireland,  at  Donegal. 

In  the  U.  States,  in  N.  Jersey,  at  Mine  Hill,  near  the  Franklin  Furnace.  In  Pcnn. ,  at 
Lancaster  abundant ;  at  the  Perkiomen  lead  mine  ;  at  the  Ueberroth  mine,  near  Bethlehem. 
In  Wisconsin,  at  Mineral  Point,  Shullsburg,  etc.  In  Minnesota,  at  Swing's  diggings,  N.  W. 
of  Dubuque,  etc.  In  Missouri  and  Arkansas,  along  with  the  lead  ores  in  Lower  Silurian 
limestone. 


OXYGEN   COMPOUNDS. — CARBONATES. 


383 


Aragonite    Group. 


ARAGONITE. 

Orthorhombic.  7  A  7  =  116°  10',  OM-i=  130°  50' ;  c:l:&  =  1-1571 
:  1-6055  :  1.  O  A  1  =  126°  15',  O  A  1-2  =  137°  15',  1-SA14,  top,  =  108° 
26'.  Crystals  usually  having  O  striated  parallel  to  the  shorter  diagonal ; 
often  tapering  from  the  presence  of  acute  domes  and  pyramids,  which  have 
unusual  indices.  Cleavage:  I  imperfect;  i-l  distinct;  \-l  imperfect. 
V Twins :  t winning-plane  7,  producing  often  hexagonal  forms,  f.  738,  compare 
figures  on  pp.  96,  97.  Twinning  often  many  times  repeated  in  the  same 
crystal,  producing  successive  reversed  layers,  the  alternate  of  which  may  be 
exceedingly  thin ;  often  so  delicate  as  to  produce  by  the  succession  a  fine 
striation  of  the  faces  of  a  prism  or  of  a  cleavage  plane.  Also  globular, 
reniform,  and  coralloidal  shapes;  sometimes  columnar,  composed  of 
straight  and  divergent  fibres ;  also  stalactitic ;  incrusting. 


737 


738 


/ 

\ 
u 

il 

/ 
I 

% 

/If 

^S^-o-'^fe 

•^ 

||i 

«v/ 

i    I  J 

I2 

4|i 

J 

y 

H. =3-5-4.  G. =2-931,  Haidinger.  Lustre  vitreous,  sometimes  inclin- 
ing to  resinous  on  surfaces  of  fracture.  Color  white ;  also  gray,  yellow, 
green,  and  violet ;  streak  uncolored.  Transparent — translucent.  Fracture 
subconchoidal.  Brittle. 

Var. — 1.  Ordinary,  (a]  Crystallized  in  simple  or  compound  crystals,  the  latter  much  the 
most  common  ;  often  in  radiating  groups  of  acicular  crystals,  (b)  Columnar ;  a  fine  fibroua 
variety  with  silky  lustre  is  called  Satin  spar,  (c}  Massive.  Stalactitic  or  stalagmitic  (either 
compact  or  fibrous  in  structure),  as  with  calcite ;  Sprudelstein  is  stalactitic  from  Carlsbad. 
Coralloidal ;  in  groupings  of  delicate  interlacing  and  coalescing  stems,  of  a  snow-white  color, 
and  looking  a  little  like  coral. 

Comp.— CaC03,  like  calcite,  =  Carbon  dioxide  44,  lime  56=100. 

Pyr.,  etc. — B.B.  whitens  and  falls  to  pieces,  and  sometimes,  when  containing  strontia,  im- 
parts a  more  intensely  red  color  to  the  flame  than  lime ;  otherwise  reacts  like  calcite. 

Diff.— See  calcite,  p.  379. 

Obs. — The  most  common  repositories  of  aragonite  are  beds  of  gypsum,  beds  of  iron  ore 
(where  it  occurs  in  coralloidal  forms,  and  is  denominated  flos-ferri,  "flower  of  iron,,"  Eisen- 
bliithe,  Germ.),  basalt,  and  trap  rock;  occasionally  it  occurs  in  lavas.  It  is  often  associated 
with  copper  and  pyrite,  galenite,  and  malachite. 

First  discovered  in  Aragon,  Spain  (whence  its  name),  at  Molina  and  Valencia.  Since 
round  at  Bilin  in  Bohemia ;  at  Herrengrund  in  Hungary,  f.  738 ;  at  Baumgarten  in  Silesia ; 


384 


DESCRIPTIVE   MINERALOGY. 


at  Leogang  in  Salzburg ;  in  Waltsch,  Bohemia,  and  many  other  places.  The  floaferri  variety 
is  found  in  great  perfection  in  the  Styrian  mines.  In  Buckinghamshirej  Devonshire,  in 
caverns;  at  Leadhills  in  Lanarkshire. 

Occurs  in  serpentine  at  Hoboken,  N.  J.;  at  Edenville,  N.  Y.;  at  the  Parish  ore  bed,  Rossie, 
N.  Y.;  at  Haddam,  Conn.;  at  New  Garden,  in  Chester  Co.,  Penn. ;  at  Wood's  Mine,  Lancas- 
ter Co.,  Penn.;  at  Warsaw,  111.,  lining  geodes. 

MANGANOCALCITE. —Composition  2MnCO3+(Ca,Mg)CO3,  with  a  little  iron  replacing  part 
of  the  manganese.  G-.  =3'037.  Color  flesh-red  to  reddish-white.  Schemnitz,  Hungary. 


WITHERITE. 

Orthorhombic.     /A  /=  118°  30',  O  A  l-i  =  128°  45' ;  c:l:d  =  1-246  : 
1*6808  :  1.     Twins  :  all  the  annexed  figures,  com- 


739 


position  parallel  to  I\  reentering  angles  some- 
times observed.  Cleavage :  I  distinct ;  also  in 
globular,  tuberose,  and  botryoidal  forms ;  struc- 
ture either  columnar  or  granular ;  also  amor- 
phous. 

H.=3-3-75.  O. =4-29-4-35.  Lustre  vitreous, 
inclining  to  resinous,  on  surfaces  of  fracture. 
Color  white,  often  yellowish,  or  grayish.  Streak 
white.  Subtransparent — translucent.  Fracture 
uneven.  Brittle. 


Comp.—BaCO  3  =  Carbon  dioxide  22  -3,  baryta  77'7— 100. 
Pyr.,  etc. — B.B.  fuses  at  2  to  a  bead,  coloring  the  llame  yel- 
lowish-green; after  fusion  reacts  alkaline.     B.B.  on  charcoal 
with  soda  fuses  easily,  and  is  absorbed  by  the  coal.    Soluble 

in  dilute  hydrochloric  acid;  this  solution,  even  when  very  much  diluted,  gives  with  sulphuric 
acid  a  white  precipitate  which  is  insoluble  in  acids. 

Diff. — Distinguishing  characters :  high  specific  gravity  ;  effervescence  with  acids ;  green 
coloration  of  the  flame  B.B. 

Obs. — Occurs  at  Alston-Moor  in  Cumberland ;  at  Fallowfield,  near  Hexham  in  Northumber- 
land ;  Tarnowitz  in  Silesia  ;  Leogang  in  Salzburg  ;  Peggau  in  Styria  ;  some  places  in  Sicily  ; 
the  mine  of  Arqueros,  near  Coquimbo,  Chili ;  near  Lexington,  Ky. ,  with  barite. 

Witherite  is  extensively  mined  at  Fallowfield,  and  is  used  in  chemical  works  in  the  manu- 
facture of  plate-glass,  and  in  France  in  making  beet- sugar. 
BBOMLITE. — Formula  as  for  barytocalcite,  but  orthorhombic  in  form. 


STRONTI ANITB . 


Orthorhombic. 


/A  /=  117°  19' 


744 


0  A 14  =  130°  5';  6:  ft:  4  =  1-1888  : 

1-6421  :l.  O/\l  =  125°  43',  0  A  I-l  =  144°  0', 
1  A  1,  mac.,  =  130°  1',  1  A  1,  brack,  =  92°  II7. 
Cleavage  :  1  nearly  perfect,  i-i  in  traces.  Crys- 
tals often  acicular  and  in  divergent  groups. 
Twins :  like  those  of  aragonite.  0  usually  stri- 
ated parallel  to  the  shorter  diagonal.  Also  in 
columnar  globular  forms ;  fibrous  and  granular. 
H. =3-5-4.  G.=3-605-3-713.  Lustre  vitre- 
ous ;  inclining  to  resinous  on  uneven  faces  of 

fracture.  Color  pale  asparagus-green,  apple-green  ;  also  white,  gray,  yel- 
low, and  yellowish-brown.  Streak  white.  Transparent — translucent, 
Fracture  uneven.  Brittle. 


OXYGEN  COMPOUNDS. CARBONATES. 


385 


Comp. — SrC03  =  Carbon  dioxide  297,  strontia  70'3 ;  but  a  small  part  of  the  strontium 
often  replaced  by  calcium. 

Pyr.,  etc. — B.B.  swells  up,  throws  out  minute  sprouts,  fuses  only  on  the  thin  edges,  and 
colors  the  flame  strontia- red ;  the  assay  reacts  alkaline  after  ignition.  Moistened  with  hydro- 
chloric acid  and  treated  either  B.B.  or  in  the  naked  lamp  gives  an  intense  red  color.  With 
soda  on  charcoal  the  pure  mineral  fuses  to  a  clear  glass,  and  is  entirely  absorbed  by  the  coal ; 
if  lime  or  iron  be  present  they  are  separated  and  remain  on  the  surface  of  the  coal.  Soluble 
in  hydrochloric  acid ;  the  dilute  solution  when  treated  with  sulphuric  acid  gives  a  white  pre- 
cipitate. 

Diff. — Differs  from  related  minerals,  not  carbonates,  in  effervescing  with  acids ;  lower 
specific  gravity  than  witherite,  and  colors  the  flame  red. 

Obs.— Occurs  at  Strontian  in  Argyleshire  ;  in  Yorkshire,  England  ;  Giant's  Causeway,  Ire- 
land ;  Clausthal  in  the  Harz  ;  Briiunsdorf ,  Saxony  ;  Leogang  in  Salzburg.  In  the  U.  States 
it  occurs  at  Schoharie,  N.  Y.,  in  granular  and  columnar  masses,  and  also  in  crystals.  At 
Muscalonge  Lake ;  at  Chaumont  Bay  and  Theresa,  in  Jefferson  Co. ,  N.  Y.  ;  Mifliin  Co. ,  Perm. 


CERUSSITE.    Weissbleierz,  Bleispath,  Germ. 


13',  0 A  1-1  =  130°  9i' ;  c\l\a=  1-1852 


745 


Orthorhombic.  /A  1=  117° 
:  1-6388  :  1.  O  A  1  =  125° 
46',  0  A  \4  =  1M°  8',  1  A  1, 
mac.,  =  130°,  1  A  1,  brach.,  = 
92°  19'.  Cleavage:  /often 
imperfect ;  2-£  hardly  less  so. 
Crystals  usually  thin,  broad, 
and  brittle  ;  sometimes  stout. 
Twins  :  very  common  ;  twin- 
ntng-plane  7,  producing  usu- 
ally cruciform  or  stellate 
forms ;  also  less  commonly, 
twinning-plane  «-3.  Rarely 
fibrous,  often  granular  mas- 
sive and  compact.  Sometimes  stalactitic. 

1-1.  =  3-3-5.  G-. =6*465-6 '480 ;  some  earthy  varieties  as  low  as  5'4. 
Lustre  adamantine,  inclining  to  vitreous  or  resinous;  sometimes  pearly; 
sometimes  sub  metallic,  if  the  colors  are  dark,  or  from  a  superficial  change. 
Color  white,  gray,  grayish-black,  sometimes  tinged  blue  or  green  by  some 
of  the  salts  of  copper;  streak  mi  colored.  Transparent — subtranslucent. 
Fracture  conchoidal.  Very  brittle. 

Comp.— PbC03= Carbon  dioxide  16'5,  lead  oxide  83 '5=100. 

Pyr.,  etc.—  In  the  closed  tube  decrepitates,  loses  carbon  dioxide,  turns  first  yellow,  and  at 
a  higher  temperature  dark  red,  but  becomes  yellow  again  on  cooling.  B.B.  on  charcoal  fuses 
very  easily,  and  in  R.  F.  yields  metallic  lead.  Soluble  in  dilute  nitric  acid  with  effervescence. 

Diff. — Unlike  anglesite,  it  effervesces  with  nitric  acid.  Characterized  by  high  specific 
gravity,  and  yielding  lead  B.B. 

Obs. — Occurs  in  connection  with  other  lead  minerals,  and  is  formed  from  galenite,  which, 
as  it  passes  to  a  sulphate,  may  be  changed  to  carbonate  by  means  of  solutions  of  calcium 
bicarbonate.  It  is  found  at  Johanngeorgenstadt ;  at  Nertschinsk  and  Beresof  in  Siberia  ;  at 
Clausthal  in  the  Harz  ;  at  Bleiberg  in  Carinthia  ;  at  Mies  and  Przibram  in  Bohemia  ;  at  Retz- 
banya,  Hungary ;  in  England,  in  Cornwall ;  near  Matlock  and  Wirksworth,  Derbyshire ;  at 
Leadhills,  Scotland  ;  in  Wicklow,  Ireland. 

Found  in  Penn. ,  at  Phenixville  ;  at  Perkiomen.     In  JV.  York,  at  the  Rossie  lead  mine.    In 
Virginia,  at  Austin's  mines,  Wythe  Co.     In  N.  Carolina,  at  King's  mine,  Davidson  Co. ,  good. 
In  Wisconsin  and  other  lead  mines  of  the  northwestern  States,  rarely  in  crystals ;  near  the 
Blue  Mounds,  Wise. ,  in  stalactites. 
25 


386  DESCRIPTIVE   MINERALOGY. 


BARYTOOALCITE. 

Monoclinic.  C—  73°  52',  1 1\  1=  106°  54',  O  A  14  —  149°  ;  c  :  I  :  d  = 
0-81035:1-29583:1.  Cleavage:  7,  perfect;  (9,  less  perfect ;  also  massive. 

H.=4.  G.  =3-6363-3-66.  Lustre  vitreous,  inclining  to  resinous.  Color 
white,  grayish,  greenish,  or  yellowish.  Streak  white.  Transparent — 
translucent.  Fracture  uneven. 

Comp. — (Ba,Ca)CO3,  where  Ba  :  Ca— 1  :  l=Barium  carbonate  66'3,  calcium  carbonate 
33-7=100. 

Pyr.,  etc. — B.B.  colors  the  flame  yellowish -green,  and  at  a  higher  temperature  fuses  on 
the  thin  edges  and  assumes  a  pale  green  color ;  the  assay  reacts  alkaline  after  ignition.  With 
the  fluxes  reacts  for  manganese.  With  soda  on  charcoal  the  lime  is  separated  as  an  infusible 
mass,  while  the  remainder  is  absorbed  by  the  coal.  Soluble  in  dilute  hydrochloric  acid. 

Obs. — Occurs  at  Alston-Moor  in  Cumberland,  in  the  Subcarboniferous  or  mountain  lime- 
stone. 

PAKISITE. — A  carbonate  containing  cerium  (also  La,Di),  and  calcium  with  6  p.  c.  fluorine. 
Exact  composition  uncertain.  In  hexagonal  crystals.  Color  brownish-yellow.  Muso  valley, 
New  Granada.  KISCHTIMITE,  from  the  gold  washing  of  the  Barsovska  river,  Urals,  is  similar 
in  composition,  but  contains  no  calcium. 

BASTNASITE  (Hamartite). — Composition  2RCO3+RF2,  with  R=Ce  :  La=2  :  3.  Analysis, 
Nordenskiold,  CO2 19'50,  LaO  45-77,  CeO  28'49,  H,O  I'Ol,  P,O,  (5 -23)  =  100.  Found  in  small 
masses  imbedded  between  allanite  crystals.  Riddarhyttan,  Sweden. 

PHOSGENITE.     Bleihornerz,  Germ. 

Tetragonal.  0 A  1^  =  132°  37';  c  =  1-0871.  Cleavage:  I  and  i-i 
bright ;  also  basal. 

H.=2'75-3.  G.=6-6*31.  Lustre  adamantine.  Color  white,  gray,  and 
yellow.  Streak  white.  Transparent — translucent.  Rather  sectile. 

Comp. — PbC03+PbCl2=Lead  carbonate  49,  lead  chloride  51—100,  or  lead  oxide  81  -9,  car- 
bon dioxide  8-1,  chlorine  13 -0=102 '9. 

Pyr.,  etc.— B.B.  melts  readily  to  a  yellow  globule,  which  on  cooling  becomes  white  and 
crystalline.  On  charcoal  in  R.F.  gives  metallic  lead,  with  a  white  coating  of  lead  chloride. 
With  a  salt  of  phosphorus  bead  previously  saturated  with  copper  oxide  gives  the  chlorine 
reaction.  Dissolves  with  effervescence  in  nitric  acid. 

Obs. — At  Crawford  near  Matlock  in  Derbyshire  ;  very  rare  in  Cornwall ;  in  large  crystals 
at  Gibbas  and  Monteponi  in  Sardinia  ;  near  Bobrek  in  Upper  Silesia. 


HYDROUS  CARBONATES. 

TRONA. 

Monoclinic.  O  A  i-i  =  103°  15'.  Cleavage :  i-i  perfect.  Often  fibrous 
or  columnar  massive. 

H.  =  2-5-3.  G.=2'll.  Lustre  vitreous,  glistening.  Color  gray  or  yel- 
lowish-white. Translucent. v  Taste  alkaline.  Not  altered  by  exposure  to 
a  dry  atmosphere. 

Comp.— Na4CaO8+3aq=rCarbon  dioxide  40-2,  soda  37'8,  water  22'0. 

Pyr.,  etc. — In  the  closed  tube  yields  water  and  carbon  dioxide.  B.B.  imparts  an  intensely 
yellow  color  to  the  flame.  Soluble  in  water,  and  effervesces  with  acids.  Reacts  alkaline 
with  moistened  test  paper. 

Obs. — The  specimen  analyzed  by  Klaproth  came  from  the  province  of  Suckenna,  two  days' 
journey  from  Fezzen,  Africa.  To  this  species  belongs  the  urao  found  at  the  bottom  of  a  lake 


OXYGEN  COMPOUNDS. CARBONATES. 


387 


in  Maracaibo,  S.  A. ,  a  day's  journey  from  Merida.     Efflorescences  of  trona  occur  near  the 
Sweetwater  river,  Rocky  Mountains,  mixed  with  sodium  sulphate  and  common  salt. 

NATRON  or  Soda  (sodium  carbonate,  Na2CO3+10aq).      THERMONATKITE,  Na2C08+aq. 
TESCIIEMACHERITE,  Ammonium  carbonate. 


Maracaibo. 


Nevada. 


GAY-LUSSITB. 

Monoclinic.  C  =  78°  27',  /A  1=  68°  50'  and  111°  10',  O  A 14  =  125 
15' ;  c:b:d  =  0-96945  :  0-67137  :  1. 
14  A  14,  adj.,  =  109°  30',  -J-  A  •}•  =  110° 
30'.  Crystals  often  lengthened,  and 
prismatic  in  the  direction  of  14 ;  also  in 
that  of  -J- ;  also  (f  r.  Nevada)  not  elongate, 
but  thin  in  the  direction  of  the  orthodia- 
gonal,  O  being  very  narrow  or  wanting ; 
surfaces  usually  uneven,  being  formed 
of  minute  subordinate  planes.  Cleav- 
age :  I  perfect ;  O  less  so,  but  giving  a 
reflected  image  in  a  strong  light. 

H.=2-3.  (l.=l'92-l-99.  Lustre  vitreous.  Color  white,  yellowish- 
white.  Streak  nncolored  to  grayish.  Translucent.  Fracture  conchoidal. 
Extremely  brittle.  Not  phosphorescent  by  friction  or  heat. 

Comp. — Na2C03  +  CaC03  +  5aq=  Sodium  carbonate  35*9,  calcium  carbonate  33 '8,  water 
30-3  =  100. 

Pyr.,  etc. — Heated  in  a  matrass  the  crystals  decrepitate  and  become  opaque.  B.B.  fuses 
easily  to  a  white  enamel,  and  colors  the  flame  intensely  yellow.  With  the  fluxes  it  behaves 
like  calcium  carbonate.  Dissolves  in  acids  with  a  brisk  effervescence  ;  partly  soluble  in  water, 
and  reddens  turmeric 

Obs. — Abundant  at  Lagunilla,  near  Merida,  in  Maracaibo,  where  its  crystals  are  dissemi- 
nated at  the  bottom  of  a  small  lake,  in  a  bed  of  clay,  covering  urao  ;  the  natives  call  it  claws 
or  nails,  in  allusion  to  its  crystalline  form.  Also  on  a  small  island  in  Little  Salt  Lake,  near 
Ragtown,  Nevada,  about  1-J  m.  S.  of  the  main  emigrant  road  to  Humboldt.  The  lake  is  in  a 
crater-shaped  basin,  and  its  waters  are  dense  and  strongly  saline. 

The  distorted  crystals  from  Sangerhausen  have  been  long  considered  pseudomorphs  after 
gay-lussite,  though  DesCloizeaux  regards  them  as  pseudomorphs  after  celestite.  It  is  cer- 
tain, however,  as  found  by  the  author,  that  pseudomorphs  of  calcium  carbonate  after  gay- 
lussite  do  occur  on  a  large  scale  in  Nevada. 


HYDROMAGNESITE. 


1  A  1=  87°  52/-88°,   0  A  24  =  137°; 
Crystals  small,  usually 
Also    amorphous ;    as 


Monoclinic.      <7=82°-830 
:  d  =  (nearly)  0-455  :  1-0973  :  1. 
acicular  or  bladed,  and  tufted, 
chalky  or  mealy  crusts. 

H.  of  crystals  3-5.  G.  =  2-l  45-2-18,  Smith  &  Brush. 
Lustre  vitreous  to  silky  or  subpearly ;  also  earthy.  Color 
and  streak  white.  Brittle. 

Comp. — 3MgC03+H2MgO2+3aq— Carbon  dioxide  36'3,  magnesia 
43-9,  water  19-8  =  100. 

Pyr.,  etc. — In  the  closed  tube  gives  off  water  and  carbon  dioxide. 
B.B.  infusible,  but  whitens,  and  the  assay  reacts  alkaline  to  turmeric 
paper.  Soluble  in  acids ;  the  crystalline  compact  varieties  are  but 
slowly  acted  upon  by  cold  acid,  but  dissolves  with  effervescence  in  hot 
acid. 


388  DESCRIPTIVE   MINERALOGY. 

Obs. — Occurs  at  Hrubschitz,  in  Moravia,  in  serpentine ;  in  Negroponte,  near  Kami ;  at 
Kaiserstuhl,  in  Baden,  impure.  In  the  U.  States,  near  Texas,  Lancaster  Co.,  Penn  •  at 
Hoboken,  N.  J. 

HYDKODOLOMITE.— Composition  3(Ca,Mg)CO3-f  aq.  From  Mt.  Somma.  PE^NITE  from 
Texas,  Pa. ,  is  similar. 

PREDAZZITE  and  PENCATITE  are  mixtures  of  calcite  and  brucite.     Tyrol. 

DAWSONITE. — In  thin-bladed,  white,  transparent  crystals  on  trachyte.  H.  =3.  G.  =2'40. 
Analysis,  Harrington,  A103  32  84,  MgO  tr.,  CaO  5 '95,  Na,O  20'20,  K.O  0'38,  H2O  11-91.  C02 
29 '88,  Si02  040=101 '56.  Regarded  as  u  a  hydrous  carbonate  of  aluminum,  calcium,  and 
sodium;  or  perhaps  as  a  hydrate  of  aluminum  with  carbonates  of  calcium  and  sodium." 
Montreal,  Canada. 

HOVITE. — Supposed  to  be  a  hydrous  carbonate  of  aluminum  and  calcium.  Soft,  white, 
and  friable;  earthy  in  fracture.  From  Hove,  near  Brighton,  with  collyrite. 


LANTHANITE. 

Orthorhombic.  /A  7  =93°  30'-94°,  Blake,  92°  46',  v.  Lang;  /A  1  =_• 
142°  36' ;  c:b:a  =  0-99898  :  1-0496  :  1,  v.  Lang.  In  thin  four-sided 
plates  or  minute  tables,  with  bevelled  edges.  Cleavage  micaceous.  Also 
hue  granular  or  earthy. 

H.=2-5  — 3.  G.  — 2-666.  Lustre  pearly  or  dull.  Color  grayish- white, 
delicate  pink,  or  yellowish. 

Comp. — LaC03+3aq=Lanthana  52-6,  carbon  dioxide  21 '3,  water  26'1=100.  There  is 
some  oxide  of  didymium  with  the  lanthana,  according  to  Smith. 

Pyr,,  etc. — In  the  closed  tube  yields  water.  B.B.  infusible  ;  but  whitens  and  becomes 
opaque,  silvery,  and  brownish ;  with  borax,  a  glass,  slightly  bluish,  reddish,  or  amethystine, 
on  cooling ;  with  salt  of  phosphorus  a  glass,  bluish  amethystine  while  hot,  red  cold,  the 
bead  becoming  opaque  when  but  slightly  heated,  and  retaining  a  pink  color.  Effervesces  in 
the  acids. 

Obs. — Found  coating  cerite  at  Bastnas,  Sweden ;  also  with  the  zinc  ores  of  the  Saucon 
valley,  Lehigh  Co.,  Pa. ;  at  the  Sandford  iron-ore  bed,  Moriah,  Essex  Co.,  N.  Y. 

TENGERITE. — Yttrium  carbonate.     As  a  coating  on  gadolinite  from  Ytterby. 

ZARATITE.  Emerald  Nickel,  Sittiman.  Nickelsmaragd,  Germ. — Composition  M3CO5  + 
6aq,  or  NiCO3  +  2H2NiO.,+4aq.  This  requires:  Carbon  dioxide  11  '8,  nickel  oxide  59 "3, 
water  28 "9  =  100.  Usually  as  an  emerald-green  coating;  thus  on  chromite  at  Texas,  Penn., 
where  it  was  first  noticed  ;  Swinaness,  Shetland ;  Cape  Hortegal,  Spain. 

REMINGTONITE.— A  hydrous  cobalt  carbonate.     Finksburg,  Md. 


HYDROZINCITE.     Zinkbluthe,  Germ. 

Massive,  earthy  or  compact.  As  incrustations,  the  crusts  sometimes  con 
centric  and  agate-like.  At  times  reniform,  pisolitic,  stalactitic. 

H.  =  2-2-5.  G.  =  3-58-3-8.  Lustre  dull.  Color  pure  white,  grayish  or 
yellowish.  Streak  shining.  Usually  earthy  or  chalk-like. 

Comp.— In  part  ZnC03  -I- 2H2ZnX)2  =  Carbon  dioxide  13 '6,  zinc  oxide  75'3,  water  11;1=:100. 

Pyr.,  etc. — In  the  closed  tube  yields  water  ;  in  other  respects  resembles  smithsonite. 

Obs. — Occurs  at  most  mines  of  zinc,  and  is  a  result  of  the  alteration  of  the  other  ores  of 
this  metal.  Found  in  great  quantities  at  the  Dolores  mine.  Udias  valley,  province  of  Santan- 
der,  in  Spain  ;  at  Bleiberg  and  Raibel  in  Carinthia ;  near  Reimsbeck,  in  Westphalia. 

In  the  U.  States,  at  Friedensville,  Pa.;  at  Linden,  in  Wisconsin;  in  Marion  Co.,  Arkansas 
(marionite) . 

AURICHALCITE. — A  cupreous  hydrozincite.  Usually  in  drusy  incrustations.  Altai ; 
Matlock,  Derbyshire  ;  Spain  ;  Lancaster,  Pa . 


OXYGEN  COMPOUNDS. — CARBONATES. 


389 


MALACHITE. 

Monoclinic.  C  '=  88°  32',  /A  7=  104°  28',  i-i  A  —l-i  =  118°  15',  Zepharo 
vich  ;  c  :  b  :  d  =  0-51155  :  1-2903  :  1.  Common  form 
f.  751  ;  also  same  with  other  terminal  planes;  also  with 
i-i  wanting  ;  also  with  i-i,  i-\  very  large,  making  a  rect- 
angular prism  ;  also  with  the  vertical  prism  very  short, 
as  in  f.  321.  Crystals  rarely  simple.  Twins  :  twinning- 
plane  i-i,  f.  750  ;  often  penetration  twins,  as  in  f.  321, 
322,  p.  99.  Cleavage  :  basal,  highly  perfect  ;  clino- 
diagonal  less  distinct.  Usually  massive  or  in  crust  ing, 
with  surface  tuberose,  botryoidal,  or  stalactitic,  and  struc- 
ture divergent  ;  often  delicately  compact  fibrous,  and 
banded  in  color  ;  frequently  granular  or  earthy. 

II.  =  3-5-4.    G.  =  3-7-4-01.    Lustre  of  crystals  adaman- 
tine, inclining  to  vitreous  ;   of  fibrous  varieties  more  or 
less  silky  ;  often  dull  and  earthy.    Color  bright  green.    Streak  paler  green. 
Translucent  —  subtranslucent  —  opaque.     Fracture  subconchoidal,  uneven. 


Oomp.  —  Cu2CO4+H20:=CuCO3  +  H2Cu02=Carbon  dioxide  19'9,  copper  oxide  71-9,  water 
8-2=100. 

Pyr.,  etc.  —  In  the  closed  tube  blackens  and  yields  water.  B.B.  fuses  at  2,  coloring-  the 
flame  emerald-green  ;  on  charcoal  is  reduced  to  metallic  copper  ;  with  the  fluxes  reacts  like 
tenorite.  Soluble  in  acids  with  effervescence. 

Diff.  —  Differs  from  other  copper  ores  of  a  green  color  in  its  effervescence  with  acids. 

Obs.  —  Green  malachite  accompanies  other  ores  of  copper.  Perfect  crystals  are  quite  rare. 
Occurs  abundantly  in  the  Urals  ;  at  Chessy  in  France  ;  at  Schwatz  in  the  Tyrol  ;  in  Cornwall 
and  in  Cumberland,  England  ;  Sandlodge  copper  mine,  Scotland  ;  Limerick,  Waterford,  and 
elsewhere,  Ireland  ;  at  Grimberg,  near  Siegen  in  Germany.  At  the  copper  mines  of  Nischne- 
Tagilsk,  belonging  to  M.  Demidoff,  a  bed  of  malachite  was  opened  which  yielded  many  tons 
of  malachite.  Also  in  handsome  masses  at  Bembe,  on  the  west  coast  of  Africa  ;  with  the 
copper  ores  of  Cuba  ;  Chili  ;  A  ustralia. 

In  JV.  Jersey,  at  New  Brunswick.  In  Pennsylvania,  near  Morgantown,  Berks  County  ;  at 
Cornwall,  Lebanon  Co.  ;  at  the  Perkiomen  and  Phenixville  lead  mines.  In  Wisconsin,  at  the 
copper  mines  of  Mineral  Point,  and  elswhere.  In  California,  at  Hughes's  mine  in  Calaveras 
Co. 

Green  malachite  admits  of  a  high  polish,  and  when  in  large  masses  is  cut  into  ta,bles,  snuff- 
boxes, vases,  etc.  Named  from  /iaAaxf/i  inaUows,  in  allusion  to  the  green  color. 

CumoCALdTE.  —  Massive.     H.  =3.    G-.=:3-90.    Color  vermilion-red.    Analysis,  Raymondi, 
Cu2O  50-45,  CaO  20"16,  CO2  24  '00,  H20  3  -20,  FeO3  0'60,  A1O3  0'20,  MgO  0'97,  SiO2 
99  '86.     Occurs  with  a  ferruginous  calcite  at  the  copper  mines  of  Canza  in  Peru. 


AZURITE.    Kupferlasur,  Germ. 

Monoclinic.  O=  87°  39';  If\I=  99°  32',  O M-l  =  138°  41';  c'.l'.d 
=  1-039  :  1-181  :  1.  O  usually  striated  parallel  with  the  clinodiagonal. 
Cleavage  :  24  rather  perfect ;  i-i  less  distinct;  I  in  traces.  Also  massive, 
and  presenting  imitative  shapes,  having  a  columnar  composition ;  also  dull 
and  earthy. 

H. =3-5-4-25.  G.— 3-5-3-831.  Lustre  vitreous,  almost  adamantine. 
Color  various  shades  of  azure-blue,  passing  into  Berlin-blue.  Streak  blue, 
lighter  than  the  color.  Transparent — subtranslucent.  Fracture  conchoidal. 
Brittle. 


390  DESCRIPTIVE    MINERALOGY. 

Oomp.— Cu3Cu2O74-H20=2CuCO3+H2CuO2=Carbon  dioxide  25'6,  copper  oxide  69-2, 
water  5  "2 =100. 

Pyr.,  etc. — Same  as  in  malachite. 

Obs. — Occurs  at  Chessy,  near  Lyons,  whence  its  name  Chessy  Copper.  Also  in  Siberia ;  at 
Moldawa  in  the  Bannat ;  at  Wheal  Buller,  near  Redruth  in  Cornwall ;  also  in  Devonshire  and 
Derbyshire. 

In  Penn.,  at  the  Perkiomen  lead  mine;  at  Phenixville,  in  crystals;  at  Cornwall.  InWis- 
consm,  near  Mineral  Point  In  California,  Calaveras  Co. ,  at  Hughes's  mine. 

According  to  Schrauf ,  who  has  given  a  crystallographic  monograph  of  the  species,  the  form 
is  closely  related  to  that  of  epidote  (Ber.  Ak.  Wien,  July  3,  1871). 


BISMUTITE.    Wismuthspath,  Germ. 

In  implanted  acicnlar  crystallizations  (pseudomorphous) ;  also  incrusting 
or  amorphous ;  pulverulent. 

H.=4-4'5.  G.  —  6-86-6-909.  Lustre  vitreous,  when  pure;  sometimes 
dull.  Color  white,  mountain-green,  and  dirty  siskin-green  ;  occasionally 
straw-yellow  and  yellowish-gray.  Streak  greenish-gray  to  colorless.  Sub- 
translucent — opaque.  Brittle. 

Oomp. — 2Bi8C3Oi8  f  9H2O,  Ramm.  (S.  Carolina) = Carbon  dioxide  0'38,  bismuth  oxide 
89-75,  water  3 -87 =100. 

Eyr.,  etc. — In  the  closed  tube  decrepitates  and  gives  off  water.  B.B.  fuses  readily,  and  on 
charcoal  is  reduced  to  bismuth,  and  coats  the  coal  with  yellow  bismuth  oxide.  Dissolves  in 
nitric  acid,  with  slight  effervescence.  Dissolves  in  hydrochloric  acid,  affording  a  deep  yellow 
solution. 

Obs. — Bismutite  occurs  at  Schneeberg  and  Johanngeorgenstadt ;  at  Joachimsthal ;  near. 
Baden;  also  in  the  gold  district  of  Chesterfield,  S.  C.  ;  in  Gaston  Co.,  N.  C.,  in  yellowish- 
white  concretions. 

LIEBIGITE  ;  VOGLITE  (Urankalk,  Germ.). — Carbonates  of  uranium  and  calcium,  from  the 
decomposition  of  uraninite.  Exact  composition  doubtful.  SCIIIIOCKEKINGITE  is  an  oxycar- 
bonate  of  uranium  (Schrauf).  Orthorhombic.  Occurs  in  six-sided  tabular  crystals.  Joachims- 
thai. 


WHEWELLITE. — An  oxalate  of  calcium.     In  minute  monoclinic  crystals  on  calcite. 

HUMBOLDTITE. — A  hydrous  oxalate  of  iron,  2FeC2O4  +  3aq.    Compact ;  earthy, 
coal  of  Koloseruk,  near  Bilin;   also  in  black  shales  at  Kettle  Point ;  in  Bosanquet,  Canada. 

MELLITE  (Honigstein,  Germ.). — Tetragonal.  In  octahedrons  ;  also  massive,  honey-yellow, 
reddish,  or  brownish,  rarely  white.  Al2Ci2Oi2+18aq= Alumina  14 '3(5,  mellitic  acid  40 '30, 
water  45  34— 100.  Artern,  Thuringia;  Luschitz,  Bohemia;  Walchow,  Moravia;  Nertschinsk, 
etc. 


HYDROCARBON  COMPOUNDS.  391 


VI.  HYDROCARBON   COMPOUNDS. 


The  Hydrogen-Carbon  Compounds  include  (1)  the  SIMPLE  HYDROCARBONS  ; 
and  (2)  the  OXYGENATED  HYDROCARBONS. 

1.  The  SIMPLE  HYDRO  CARBONS  embrace  : 

(a)  The  Marsh  Gas  series.  General  formula  CnII2n+2.  Here  belong  the 
liquid  naphthas,  the  more  volatile  parts  of  petroleum ;  also  the  butter-like 
solids  scheererite  and  ehrismatite. 

PETROLEUM. — Mineral  oil.  Kerosene.  Bergol,  Steinol,  Era 51,  Germ.  Petroleum  is  a  thick  to 
thin  fluid.  Color  yellow  or  brown,  or  colorless ;  translucent  to  transparent.  The  specific  gravity 
varies  from  0  '7  to  0  '9.  Chemically  it  consists  essentially  of  carbon  and  hydrogen  ;  contain- 
ing several  members  of  the  naphtha  group,  as  also  the  oils  of  the  ethylerie  series,  and  the 
paraffins.  The  proportion  of  the  latter  constituents  increases  with  the  increase  of  the  density 
or  viscidity  of  the  fluid.  It  grades  insensibly  into  pittasphalt,  and  that  into  solid  bitumen. 

Occurs  in  rocks  or  deposits  of  nearly  all  geological  ages,  from  the  Lower  Silurian  to  the 
present  epoch.  It  is  associated  most  abundantly  with  argillaceous  shales  and  sandstones,  but 
is  found  also  permeating  limestones,  giving  them  a  bituminous  odor,  and  rendering  them 
sometimes  a  considerable  source  of  oil.  From  these  oliferous  shales  and  limestones  the  oil 
often  exudes,  and  appears  floating  on  the  streams  or  lakes  of  the  region,  or  rises  in  oil  springs. 
It  also  exists  collected  in  subterranean  cavities  in  certain  rocks,  whence  it  issues  in  jets  or 
fountains  whenever  an  outlet  is  made  by  boring.  These  cavities  are  situated  mostly  along 
the  course  of  gentle  anticlinals  in  the  rocks  of  the  region ;  and  it  is  therefore  probable,  as  has 
been  suggested,  that  they  originated  for  the  most  part  in  the  displacements  of  the  strata  caused 
by  the  slight  uplift.  The  oil  which  fills  the  cavities  has  ordinarily  been  derived  from  the 
subjacent  rocks ;  for  the  strata,  in  which  the  cavities  exist,  are  frequently  barren  sandstones. 

Obtained  in  large  quantities  from  the  oil  wells  of  Pennsylvania  ;  also  found  in  eastern  Vir- 
ginia, Kentucky,  Ohio,  Illinois,  Michigan,  and  New  York.  In  Canada,  at  several  places  ;  in 
southern  California  ;  in  Mexico  ;  Trinidad. 

Some  well-known  foreign  localities  are  :  Rangoon,  Burmah  ;  western  shore  of  the  Caspian 
Sea ;  in  Parma,  Italy  ;  Sicily  ;  Galicia ;  Tegernsee,  Bavaria  ;  Hanover. 


(b)  The  Olefiant  or  Ethylene  series.  General  formula  CnH2n.  Here 
belong  the  pittoliuin  group  of  liquids,  OY  pittas phalts  (mineral  tar),  and  the 
paraffins. 

PARAFFIN  GROUP.  —Wax-like  in  consistence ;  white  and  translucent.  Sparingly  soluble  in 
alcohol,  rather  easily  in  ether,  and  crystallizing  more  or  less  perfectly  from  the  solutions.  G-. 
about  0 '85-0 -98.  Melting  point  for  the  following  species,  33°-90:>.  The  different  species 
varying  in  the  value  of  /i,  vary  also  in  boiling  point,  and  other  characters. 

Paraffins  occur  in  the  Pennsylvania  petroleum,  a  freezing  mixture  reducing  the  tempera- 
ture being  sufficient  to  separate  it  in  crystals.  Also  in  the  naphtha  of  the  Caspian,  in  Ran- 
goon tar,  and  many  other  liquid  bitumens.  It  is  a  result  of  the  destructive  distillation  of 
peat,  bituminous  coal,  lignite,  coaly  or  bituminous  shales,  most  viscid  bitumens,  wood-tar, 
and  many  other  substances. 

The  name  is  from  the  Latin  parum,  little,  and  affinti,  alluding  to  the  feeble  affinity  for  other 
substances,  or,  in  other  words,  its  chemical  indifference. 

To  the  Paraffin  Group  belong  : 

URPETIIITE.— Consistency  of  soft  tallow.  Melting  point  39°  C.  Soluble  in  cold  ether. 
Urpeth  Colliery. 


392  DESCRIPTIVE   MINERALOGY. 

HATCHETTITE. — In  thin  plates  or  massive.  Color  yellowish,  or  greenish- white  ;  blackens 
on  exposure.  Melting  point  46°  C.  In  the  coal-measures  of  Glamorganshire ;  Rossitz, 
Moravia. 

OZOCERITE. — Like  wax  or  spermaceti  in  appearance  and  consistency.  G.  =0'85-0'90. 
Colorless  to  white  when  pure  ;  often  leek-green,  yellowish,  brownish -yellow,  brown.  Trans- 
lucent. Greasy  to  the  touch.  Fusing  point  56°  to  63°  C.  Occurs  in  beds  of  coal,  or  associ- * 
ated  bituminous  deposits  ;  that  of  Slanik,  Moldavia,  beneath  a  bed  of  bituminous  clay  shale  ; 
in  masses  of  sometimes  80  to  100  Ibs.,  at  the  foot  of  the  Carpathians,  not  far  from  beds  of 
coal  and  salt;  that  of  Boryslaw  in  a  bituminous  clay  associated  with  calciferous  beds  in  the 
formation  of  the  Carpathians,  in  masses.  The  same  compound  has  been  obtained  from  mine- 
ral coal,  peat,  and  petroleum,  mineral  tar,  etc.,  by  destructive  distillation.  Named  from  6s w, 
smell,  and  w/poc,  wax,  in  allusion  to  the  odor. 

ELATERITE. — Massive,  soft,  elastic;  often  like  india-rubber,  though  sometimes  hard  and 
brittle.  It  is  found  at  Castleton  in  Derbyshire,  in  the  lead  mine  of  Odin,  along  with  lead  ore 
and  calcite.  in  compact  reniform  or  fungoid  masses,  and  is  abundant.  Also  reported  from  St. 
Bernard's  Well,  Edinburgh,  etc. 

ZIETRISIKITE  and  PYROPISSITE  belong  here. 


(c)  The  Camphene  Series.     General  Formula  (VH^-^ 

FICHTELITE.  —In  white  monoclinic  crystals.  Brittle.  Solidifies  at  36°  C.  Soluble  in  ether. 
The  mineral  occurs  in  the  form  of  shining  scales,  flat  crystals,  and  thin  layers  between  the 
rings  of  growth  and  throughout  the  texture  of  pine  wood  (identical  in  species  with  the  modern 
Pinus  sylvestris)  from  peat  beds  in  the  vicinity  of  Redwitz  in  the  Fichtelgebirge,  North 
Bavaria.  In  peat  near  Sobeslau ;  in  a  log  of  Pinus  Australis. 

HARTITE. — Resembles  fichtelite,  but  melts  at  74°-75°  C.  Found  in  a  kind  of  pine,  like 
fichtelite.  but  of  a  different  species,  the  Pence  acerosa  linger,  belonging  to  an  earlier  geological 
epoch.  From  the  brown-coal  beds  of  Oberhart,  near  Gloggnitz,  not  far  from  Vienna.  Reported 
also  from  Rosenthal  near  Koflach  in  Styria,  and  Pravali  in  Carinthia. 

DINITE  and  IXOLYTE  belong  here. 


(d)  The   Benzole   Series,     General   Formula   CnH2n_6.      Including  the 
Benzole  liquids  and  KONLITE  from  Uznach,  and  Redwitz. 

(e)  The  JNaphthalin  Series.     General  Formula  Cnll^.^. 

NAPHTHALIN. — Occurs  in  Rangoon  tar.  IDRIALITE,  crystalline  in  the  pure  state.  Color 
white.  In  nature  found  only  impure,  being  mixed  with  cinnabar,  clay,  and  some  pyrite  and 
gypsum  in  a  brownish -black  earthy  material,  called  from  its  combustibility  and  the  presence 
of  mercury,  inflammable  cinnabar  (Quecksilberbranderz).  Idria,  Spain.  ARAGOTITE,  from 
New  Almaden  Mine,  Cal.,  is  related  to  idrialite. 


2.  The  OXYGENATED  HYDROCARBONS  embrace  different  groups  having 
ratios  of  C  :  II  varying  from  1  :  2  to  5  :  5^,  or  less.  Some  of  the  more 
important  are : 

GEOCERITE.  Wax -like.  Color  white.  Melting  point  near  80°  C.  ;  after  fusion  solidifies  as 
a  yellowish  wax,  hard  but  not  very  brittle.  Soluble  in  alcohol  of  80  p.  c.  C28H56O2=: Carbon 
79'24,  hydrogen  13*21,  oxygen  7'55=100.  From  the  same  dark-brown  brown  coal  of  Gester- 
witz  that  afforded  the  geomyricite,  and  from  the  same  solution. 

GEOMYRICITE. — Wax-like.  Obtained  in  a  pulverulent  form  from  a  solution,  the  grains  con- 
sisting of  acicular  crystals.  Color  white.  Melting  point  80°-83J  C.  After  fusion  has  the 
aspect  of  a  yellowish  brittle  wax.  Soluble  easily  in  hot  absolute  alcohol  and  ether,  but 
slightly  in  alcohol  of  80  p.  c.  C34H68O2  =  Carbon  80;59,  hydrogen  13 '42,  oxygen  5 '99=100. 
Burns  with  a  bright  flame.  Occurs  at  the  Gesterwitz  brown  coal  deposit,  in  a  dark  broicn 
layer. 


HYDKOCAEBON  COMPOUNDS.  393 


SUCCINITE.    Amber.     Succin,  Ambre,  Fr.     Bernstein,  Germ. 

In  irregular  masses,  without  cleavage.  H.  =  2-2'5.  G.  =  1'065-1'081. 
Lustre  resinous.  Color  yellow,  sometimes  reddish,  brownish,  and  whitish, 
often  clouded.  Streak  white.  Transparent — translucent.  Tasteless.  Elec- 
tric on  friction.  Fuses  at  287°  C.,  but  without  becoming  a  flowing  liquid. 

Comp.— Ratio  f  or  C  :  H  :  O=40  :  64  :  4=Carbon  78'94,  hydrogen  10'53,  oxygen  10'53  = 
100.  But  amber  is  not  a  simple  resin.  According  to  Berzclius,  it  consists  mainly  (85  to  90 
p.  c.)  of  a  resin  which  resists  all  solvents  (properly  the  species  succinite),  along  with  two  other 
resins  soluble  in  alcohol  and  ether,  an  oil,  and  2^  to  6  p.  c.  of  succinic  acid.  Amber  is  hardly 
acted  on  by  alcohol.  Burns  readily  with  a  yellow  flame,  emitting  an  agreeable  odor,  and 
leaves  a  black,  shining,  carbonaceous  residue. 

Obs. — Occurs  abundantly  on  the  Prussian  coast  of  the  Baltic ;  occiirring  from  Dantzig  to 
Memel ;  also  on  the  coast  of  Denmark  and  Sweden ;  in  Galicia,  near  Lemberg,  and  at  Miszau  ; 
in  Poland ;  in  Moravia,  at  Boskowitz,  etc.  ;  in  the  Urals,  Russia  ;  near  Christiania,  Norway ; 
in  Switzerland,  near  Bale;  in  France,  near  Paris,  in  clay.  In  England,  near  London,  and  on 
the  coast  of  Norfolk,  Essex,  and  Suffolk.  In  various  parts  of  Asia.  Also  near  Catania,  on 
the  Sicilian  coast.  It  has  been  found  in  various  parts  of  the  Green  sand  formation  of  the 
United  States,  either  loosely  imbedded  in  the  soil,  or  engaged  in  marl  or  lignite,  as  at  Gay 
Head  or  Martha's  Vineyard,  near  Trenton,  and  also  at  Camden  in  New  Jersey,  and  at  Cape 
Sable,  near  Magothy  river  in  Maryland.  In  the  royal  museum  at  Berlin  there  is  a  mass 
weighing1  18  Ibs.  Another  in  the  kingdom  of  Ava,  India,  is  nearly  as  large  as  a  child's  head, 
and  weighs  "|  Ibs. 

It  is  now  fully  ascertained  that  arnber  is  a  vegetable  resin  altered  by  fossilization.  This 
is  inferred  both  from  its  native  situation  with  coal,  or  fossil  wood,  and  from  the  occurrence 
of  insects  incased  in  it.  Of  these  insects,  some  appear  evidently  to  have  struggled  af  Ler  being 
entangled  in  the  then  \  iscous  fluid  ;  and  occasionally  a  leg  or  a  wing  is  found  some  distance 
from  the  body,  which  had  been  detached  in  the  effort  to  escape. 

Amber  was  early  known  to  the  ancients,  and  called  ij/enrpov,  electrum,  whence,  on  account 
of  its  electrical  susceptibilities,  we  have  derived  the  word  electricity.  It  was  named  by  some 
lyncurium,  though  this  name  was  applied  by  Theophrastus  also  to  a  stone,  probably  to  zircon  or 
tourmaline,  both  minerals  of  remarkable  electrical  properties. 

Other  related  resins  are:  COPALITE  (retinite  pt.)  from  Highgate  Hill,  near  London; 
KRANTZITE,  Nieiiburg ;  WALCIIOWITE,  Walchow,  Moravia ;  AMBRITE,  N.  Zealand ;  BATII- 
VILLITE,  occurring  in  the  torbanite,  or  Boghead  coal  of  Bathviile,  Scotland ;  torbanite  is 
related  to  it.  SIEQBUBGITE,  SCHRAUFITE,  AMBROSINE,  DUXITE. 

XYLORETINITE  (hartine).— C  :  H  :  O=40  :  64  :  4.  BOMBICCITE,  C  :  H  :  O=13  :  7  :  1,  in 
lignite  in  the  valley  of  the  Arno,  Tuscany.  LEUCOPETRITE.  C  :  H  :  O=50  :  84  :  3.  Ges- 
terwitz,  near  Weissenf els.  EUOSMITE.  C  :  H  :  O— 34  :  29  :  2,  from  the  brown  coal  at  Baiershof 
in  the  Fichtelgebirge.  ROSTHORNITE.  C  :  H  :  0—24  :  40  :  1.  In  coal  at  Sonnberg,  Carin- 
thia.  The  above  species  are  soluble  in  ether. 

SCLERETINITE.  —  C  :  H  :  O=:40  :  64  :  4.     Insoluble  in  ether.     Wigan,  England. 

PYRORETINITE,  JAULINGITE,  REUSSINITE,  GUYAQUILLITE,  WHEELERITE  (New  Mexico), 
etc.  Ratio  of  C  :  H=5  :  7  to  5  :  6£. 

MIDDLETONITE,  STANEKITE,  ANTHRACOXENITE.  Ratio  of  C  :  H=5  :  5$-  or  less.  Insolu- 
able  in  ether  or  alcohol. 

TASMANITE  and  DYSODILE  are  remarkable  in  containing  sulphur,  replacing  part  of  the 
oxygen. 

The  ACID  OXYGENATED  HYDROCARBONS  include  Butyrellite  (Bogbutter), 
Succinellite,  Dopplerite,  etc.,  etc. 


394  DESCRIPTIVE   MINERALOGY. 


APPENDIX    TO    HYDKOCARBONS. 

ASPHALTUM.    Bitumen.     Asphalt,  Mineral  Pitch.     Bergpech,  Erdpech,  Gei^m. 

Asphaltum,  or  mineral  pitch,  is  a  mixture  of  different  hydrocarbons,  part 
of  which  are  oxygenated.  Its  ordinary  characters  are  as  follows: 

Amorphous.  &.  =  1-1  '8 ;  sometimes  higher  from  impurities.  Lustre 
like  that  of  black  pitch.  Color  brownish-black  and  black.  Odor  bitumi- 
nous. Melts  ordinarily  at  90°  to  100°  C.,  and  burns  with  a  bright  flame. 
Soluble  mostly  or  wholly  in  oil  of  turpentine,  and  partly  or  wholly  in  ether ; 
commonly  partly  in  alcohol. 

The  more  solid  kinds  graduate  into  the  pittasphalts  or  mineral  tar,  and 
through  these  there  is  a  gradation  to  petroleum.  The  fluid  kinds  change 
into  the  solid  by  the  loss  of  a  vaporizable  portion  on  exposure,  and  also  by 
a  process  of  oxidation,  which  consists  first  in  a  loss  of  hydrogen,  and  finally 
in  the  oxygenation  of  a  portion  of  the  mass. 

Obs.— Asphaltum  belongs  to  rocks  of  no  particular  age.  The  most  abundant  deposits  are 
superficial.  But  these  are  generally,  if  not  always,  connected  with  rock  deposits  containing 
some  kind  of  bituminous  material  or  vegetable  remains. 

Some  of  the  noted  localities  of  asphaltum  are  the  region  of  the  Dead  Sea,  or  Lake  Asphal- 
tites,  on  Trinidad ;  at  various  places  in  S.  America,  as  at  Caxitambo,  Peru  ;  at  Berengela, 
Peru,  not  far  from  Arica  (S.);  in  California,  near  the  coast  of  St.  Barbara.  Also  in  smaller 
quantities,  sometimes  disseminated  through  shale,  and  sandstone  rocks,  and  occasionally  lime- 
stones, or  collected  in  cavities  or  seams  in  these  rocks ;  near  Matlock,  Derbyshire ;  Poldice 
mine  in  Cornwall ;  Val  de  Travers,  Neuchatel ;  impregnating  dolomite  on  the  island  of  Brazza 
in  Dalmatia ;  in  the  Caucasus  ;  in  gneiss  and  mica  schist  in  Sweden. 

The  following  substances  are  closely  related  to  asphaltum,  and,  like  it,  are  mixtures  of  un- 
determined carbohydrogens. 

GrRAHAMiTE,  Wurtz.  — Resembles  the  preceding  in  its  pitch-black,  lustrous  appearance;  H. 
=2;  G.  =1-145.  Soluble  mostly  in  oil  of  turpentine  ;  partly  in  ether,  naphtha,  or  benzole  ; 
not  at  all  in  alcohol ;  wholly  in  chloroform  and  carbon  disulphide.  No  action  with  alkalies  or 
hot  nitric  or  hydrochloric  acid.  Melts  only  imperfectly,  and  with  a  decomposition  of  the 
surface  ;  but  in  this  state  the  interior  may  be  drawn  into  long  threads.  Occurs  in  W.  Vir- 
ginia, about  20  m.  in  an  air  line  S.  of  Parkersburg,  filling  a  fissure  (shrinkage  fissure)  in  a 
sandstone  of  the  Carboniferous  formation ;  and  supposed  to  be,  like  the  albertite,  an  inspis- 
sated and  oxygenated  petroleum. 

ALBERTITE,  Robb. — Differs  from  ordinary  asphaltum  in  being  only  partially  soluble  in  oil 
of  turpentine,  and  in  its  very  imperfect  fusion  when  heated.  It  has  H.  =1-2  ;  G.  =:1'097; 
lustre  brilliant,  pitch-like  ;  color  jet-black.  Softens  a  little  in  boiling  water  ;  in  the  flame  of 
a  candle  shows  incipient  fusion.  According  to  imperfect  determinations,  only  a  trace  soluble 
uxalcohol  ;  4  p.  c.  in  ether ;  30  in  oil  of  turpentine.  Occurs  filling  an  irregular  fissure  in 
rocks  of  the  Subcarboniferous  age  (or  Lower  Carboniferous)  in  Nova  Scotia,  and  is  regarded 
as  an  inspissated  and  oxygenated  petroleum.  This  and  the  above  are  very  valuable  in  gas- 
making. 

PIAUZITE. — An  asphalt-like  substance,  remarkable  for  its  high  melting  point,  315°  C.  It 
occurs  slaty  massive  ;  color  brownish-  or  greenish-black  ;  thin  splinters  colophonite-brown  by 
transmitted  light ;  streak  light  brown,  amber-brown  ;  H.=l  '5  ;  Gr.  —1  '220  ;  1  '186,  Kenngott. 
It  comes  from  a  bed  of  brown  coal  at  Piauze,  near  Neustadt  in  Carniola  ;  on  Mt.  Chum,  near 
Tiiffer  in  Styria 

WOLLONGONGITE,  Silliman. — Occurs  in  cubic  blocks  without  lamination.  Fracture  broad 
conchoidal.  Color  greenish-  to  brownish-black.  Lustre  resinous.  In  the  tube  does  not  melt, 
but  decrepitates  and  gives  off  oil  and  gas  ;  yields  by  dry  distillation  82  '5  p.  c.  volatile  matter. 
Insoluble  in  ether  or  benzole.  New  South  Wales. 


HYDROCARBON    COMPOUNDS.  395 


MINERAL    COAL 

The  distinguishing  characters  of  Mineral  Coal  are  as  follows :  Compact 
massive,  without  crystalline  structure  or  cleavage ;  sometimes  breaking 
with  a  degree  of  regularity,  but  from  a  jointed  rather  than  a  cleavage  struc- 
ture. Sometimes  laminated  ;  often  faintly  and  delicately  banded,  successive 
layers  differing  slightly  in  lustre. 

H.  =  0-5-2-5.  G.  =  l-l-80.  Lustre  dull  to  brilliant,  and  either  earthy, 
resinous,  or  submetallic.  Color  black,  grayish-black,  brownish-black,  and 
occasionally  iridescent ;  also  sometimes  dark  brown.  Opaque.  Fracture 
conchoidal — uneven.  Brittle ;  rarely  somewhat  sectile.  Without  taste, 
except  from  impurities  present.  Insoluble  or  nearly  so  in  alcohol, 'ether, 
naphtha,  and  benzole.  Infusible  to  subf  usible  ;  but  often  becoming  a  soft, 
pliant,  or  paste-like  mass  when  heated.  On  distillation  most  kinds  afford 
more  or  less  of  oily  and  tarry  substances,  which  are  mixtures  of  hydrocar- 
bons and  paraffin. 

Mineral  coal  is  made  up  of  different  kinds  of  hydrocarbons,  with  perhaps 
in  some  cases  free  carbon. 

Var. — The  variations  depend  partly  (1)  on  the  amount  of  the  volatile  ingredients  afforded 
on  destructive  destination ;  or  (2)  on  the  nature  of  these  volatile  compounds,  for  ingredients 
of  similar  composition  may  differ  widely  in  volatility,  etc.  ;  (3)  on  structure,  lustre,  and  other 
physical  characters. 

1.  ANTHRACITE.    H.=2-2-5.    G.— 1'32-1-7,  Pennsylvania;  1-81,  Rhode  Island  ;  1 '26-1 '36, 
South  Wales.     Lustre  bright,  often  submetallic,  iron  black,  and  frequently  iridescent.     Frac- 
ture conchoidal.    Volatile  matter  after  drying  3  to  G  p.  c.    Burns  with  a  feeble  flame  of  a  pale 
color.     The  anthracites  of  Pennsylvania  contain  ordinarily  85  to  93  per  cent,  of  carbon  ;  those 
of  South  Wales,  88  to  95  ;  of  France,  80  to  83 ;  of  Saxony,  81  ;  of  southern  Russia,  some- 
times 94  per  cent.     Anthracite  graduates  into  bituminous  coal,  becoming  less  hard,  and  con- 
taining more  volatile  matter ;  and  an  intermediate  variety  is  called  free-burning  anthracite. 

BITUMINOUS  COALS  (Steinkohie  pt. ,  Germ.}.  Under  the  head  of  Bituminous  Coals,  a 
number  of  kinds  are  included  which  differ  strikingly  in  the  action  of  heat,  and  which  there- 
fore are  of  unlike  constitution.  They  have  the  common  characteristic  of  burning  in  the  fire 
with  a  yellow,  smoky  flame,  and  giving  out  on  distillation  hydrocarbon  oils  or  tar,  and  hence 
the  name  bituminous.  The  ordinary  bituminous  coals  contain  from  5  to  15  p.  c.  (rarely  10  or 
17)  of  oxygen  (ash  excluded) ;  while  the  so-called  brown  coal  or  lignite  contains  from  20  to 
30  p.  c.,  after  the  expulsion,  at  100°  C.,  of  15  to  36  p.  c.  of  water.  The  amount  of  hydrogen 
in  each  is  from  4  to  7  p.  c.  Both  have  usually  a  bright,  pitchy,  greasy  lustre  (whence  often 
called  Peclikohle  in  German),  a  firm  compact  texture,  are  rather  fragile  compared  with  anthra- 
cite, and  have  G-.  =1*14-1  "40.  The  brown  coals  have  often  a  brownish-black  color,  whence 
the  name,  and  more  oxygen,  but  in  these  respects  and  others  they  shade  into  ordinary  bitu- 
minous coals.  The  ordinary  bituminous  coal  of  Pennsylvania  has  Gr.  =1-26-1*37 ;  of  New- 
castle, England,  1-27;  of  Scotland,  1-27-1-32;  of  France,  1*2-1 '33;  of  Belgium,  1-27-1  "3. 
The  most  prominent  kinds  are  the  following: 

2.  CAKING  COAL.     A  bituminous  coal  which  softens  and  becomes  pasty  or  semi-viscid  in 
the  fire.     This  softening  takes  place  at  the  temperature  of  incipient  decomposition,  and  is 
attended  with  the  escape  of  bubbles  of  gas.     On  increasing  the  heat,  the  volatile  products 
which  result  from  the  ultimate  decomposition  of  the  softened  mass  are  driven  off,  and  a 
coherent,    grayish-black,  cellular,  or  fritted  mass  (coke)  is  left.     Amount  of  coke  left  (or  part 
not  volatile)  varies  from  50  to  85  p.  c.     Byerite  is  from  Middle  Park,  Colorado. 

3.  NON-CAKING  COAL.     Like  the  preceding  in  all  external  characters,  and  often  in  ultimate 
composition  ;  but  burning  freely  without  softening  or  any  appearance  of  incipient  fusion. 

4.  CANNEL  COAL  (Parrot  Coal).     A  variety  of  bituminous  coal,  and  often  caking ;  but  dif- 
fering from  the  preceding  in  texture,  and  to  some  extent  in  composition,  as  shown  by  its 
products  on  distillation.     It  is  compact,  with  little  or  110  lustre,  and  without  any  appearance 
of  a  banded  structure;   and  it  breaks  with  a  conchoidal  fracture  and  smooth  surfaces;  color 
dull  black  or  grayish-black.     On  distillation  it  affords,  after  drying,  40  to  00  of  volatile  mat- 
ter, and  the  material  volatilized  includes  a  large  proportion  of  burning  and  lubricating  oils, 


396  DESCRIPTIVE   MINERALOGY. 

much  larger  than  the  above  kinds  of  bituminous  coal ;  whence  it  is  extensively  used  for  fhe 
manufacture  of  such  oils.  It  graduates  into  oil-producing  coaly  shales,  the  more  compact  of 
which  it  much  resembles. 

5.  TORBANITE.     A  variety  of  cannel  coal  of  a  dark  brown  color,  yellowish  streak,  without 
lustre,  having  a  subconchoidal  fracture;  H.  =2-25;  G.  =  1 '17-1 -2.     Yields  over  60  p.  c.  of 
volatile  matter,  and  is  used  for  the  production  of  burning  and  lubricating  oils,  paraffin,  illu- 
minating gas.     From  Torbane  Hill,  near  Bathgate  in  Linlithgowshire,  Scotland.     Also  called 
Boghead  Cannel. 

6.  BROWN  COAL  (Braunkohle   Germ.,  Pechkohle  pt.    Germ.,  Lignite).     The  prominent 
characteristics  of  brown  coal  have  already  been  mentioned.     They  are  non-caking,  but  afford 
a  large  proportion  of  volatile  matter.     They  are  sometimes  pitch-black  (whence  Pechkohle 
pt.   Germ.},  but  often  rather  dull  and  brownish-black.     G.  =  1*15-1  '3  ;  sometimes  higher  from 
impurities.     It  is  occasionally  somewhat  lamellar  in  structure.     Brown  coal  is  often  called 
lignite.     But  this  term  is  sometimes  restricted  to  masses  of  coal  which  still  retain  the  form  of 
the  original  wood.     Jet  is  a  black  variety  of  brown  coal,  compact  in  texture,  and  taking  a 
good  polish,  whence  its  use  in  jewelry. 

7.  EARTHY  BROWN  COAL  (Erdige  Braunkohle]  is  a  brown  friable  material,  sometimes  form- 
ing layers  in  beds  of  brown  coal.     Bat  it  is  in  general  not  a  true  coal,  a  considerable  part  of 
it  being  soluble  in  ether  and  benzole,  and  often  even  in  alcohol ;  besides  affording  largely  of 
oils  and  paraffin  on  distillation. 

Comp. — Most  mineral  coal  consists  mainly,  as  the  best  chemists  now  hold,  of  oxygenated 
hydrocarbons.  Besides  oxygenated  hydrocarbons,  there  may  also  be  present  simple  hydrocar- 
bons (that  is,  containing  no  oxygen). 

Sulphur  is  present  in  nearly  all  coals.  It  is  supposed  to  be  usually  combined  with  iron, 
and  when  the  coal  affords  a  red  ash  on  burning,  there  is  reason  for  believing  this  true.  But 
Percy  mentions  a  coal  from  New  Zealand  (anal.  18)  which  gave  a  peculiarly  white  ash, 
although  containing  2  to  3  p.  c.  of  sulphur,  a  fact  showing  that  it  is  present  not  as  a  sulphide 
of  iron,  but  as  a  constituent  of  an  organic  compound.  The  discovery  by  Church  of  a  resin 
containing  sulphur  (see  TASMANITE,  p.  393),  gives  reason  for  inferring  that  it  may  exist  in 
this  coal  in  that  state,  although  its  presence  as  a  constituent  of  other  organic  compounds  is 
quite  possible. 

The  chemical  relations  of  the  different  kinds  of  coals  will  be  understood  from  the  follow- 
ing analyses : 

Carbon.  Hydrogen.  Oxygen.  Nitrogen.  Sulphur.  Ash. 

1.  Anthracite,  S.  Wales  92-56  333  2  53                             1-58 

2.  Caking  Coal,' Northumberland  78-69  (rOO  10-07  2'37  1'51  1-3(5 

3.  Non-Caking  Coal,  Zwickau  80'25  4'01  10'98  0'49  2-99  1'57 

4.  Cannel  Coal,  Wigan  80'07  5 '53  8'10  2-12  1 '50  2-70 

5.  Torbanite,  Torbane  Hill  64-02  8-90  5 '66  0'55  0'50  20  32 

6.  Brown  Coal,  Meissen,  Sax.  58  "90  5-36  21-63  6 '61  7 '50 

Coal  occurs  in  beds,  interstratified  with  shales,  sandstones,  and  conglomerates,  and  some- 
times limestones,  forming  distinct  layers,  which  vary  from  a  fraction  of  an  inch  to  30  feet  or 
more  in  thickness.  In  the  United  States,  the  anthracites  occur  east  of  the  Alleghany  range, 
in  rocks  that  have  undergone  great  contortions  and  fracturings,  while  the  bituminous  are 
found  farther  west,  in  rocks  that  have  been  less  disturbed  ;  and  this  fact  and  other  observa- 
tions have  led  some  geologists  to  the  view  that  the  anthracites  have  lost  their  bitumen  by  the 
action  of  heat.  The  origin  of  coal  is  mainly  vegetable,  though  animal  life  has  contributed 
somewhat  to  the  result.  The  beds  were  once  beds  of  vegetation,  analogous,  in  most  respects, 
in  mode  of  formation  to  the  peat  beds  of  modern  times,  yet  in  mode  of  burial  often  of  a  very 
different  character.  This  vegetable  origin  is  proved  not  only  by  the  occurrence  of  the  leaves, 
stems,  and  logs  of  plants  in  the  coal,  but  also  by  the  presence  throughout  its  texture,  in 
many  cases,  of  the  forms  of  the  original  fibres ;  also  by  the  direct  observation  that  peat  is 
a  transition  state  between  unaltered  vegetable  debris  and  brown  coal,  being  sometimes  found 
passing  completely  into  true  brown  coal.  Peat  differs  from  true  coal  in  want  of  homo- 
geneity, it  visibly  containing  vegetable"  fibres  only  partially  altered  ;  and  wherever  changed 
to  a  fine-textured  homogeneous  material,  even  though  hardly  consolidated,  it  may  be  true 
brown  coal. 

Extensive  beds  of  mineral  coal  occur  in  Great  Britain,  covering  11,859  square  miles;  in 
France  about  1,719  sq.  m.  ;  in  Spain  about  3,408  sq.  m. ;  in  Belgium  518  sq.  m.  ;  in  Nether- 
lands, Prussia,  Bavaria,  Austria,  northern  Italy,  Silesia,  Spain,  Russia  on  the  south  near  the 
Azof,  and  also  in  the  Altai.  It  is  found  in  Asia,  abundantly  in  China,  etc.,  etc. 

In  the  United  States  there  are  four  separate  coal  areas.  One  of  these  areas,  the  Appala- 
chian coal  field,  commences  on  the  north,  in  Pennsylvania  and  southeastern  Ohio,  and  sweep  • 


HYDROCARBON  COMPOUNDS.  397 

ing  south  over  western  Virginia  and  eastern  Kentucky  and  Tennessee  to  the  west  of  the 
Appalachians,  or  partly  involved  in  their  ridges,  it  continues  to  Alabama,  near  Tuscaloosa, 
where  a  bed  of  coal  has  been  opened.  It  has  been  estimated  to  cover  60,000  sq.  m.  A  sec- 
ond coal  area  (the  Illinois)  lies  adjoining  the  Mississippi,  and  covers  the  larger  part  of  Illinois, 
though  much  broken. into  patches,  and  a  small  northwest  part  of  Kentucky.  A  third  covers 
the  central  portion  of  Michigan,  not  far  from  5,000  sq.  m.  in  area.  Besides  these,  there  is  a 
smaller  coal  region  (a  fourth)  in  Rhode  Island.  The  total  area  of  workable  coal  measures  in 
the  United  States  is  about  125,000  sq.  in.  Out  of  the  borders  of  the  United  States,  on  the 
northeast,  commences  a  fifth  coal  area,  that  of  Nova  Scoiia  and  New  Brunswick,  which 
covers,  in  connection  with  that  of  Newfoundland,  18,000  sq.  m. 

The  mines  of  western  Pennsylvania,  those  of  the  States  west,  and  those  of  Cumberland  or 
Frostburg,  Maryland,  Richmond  or  Chesterfield,  Va. ,  and  other  mines  south,  are  bituminous. 
Those  of  eastern  Pennsylvania  constituting  several  detached  areas— one,  the  Schuylkill  coal 
field — another,  the  Wyoming  coal  field — those  of  Rhode  Island  and  Massachusetts,  and  some 
patches  in  Virginia,  are  anthracites.  Cancel  coal  is  found  near  Greensburg,  Beaver  Co.,  Pa., 
in  Kenawha  Co  ,  Va.,  at  Peytona,  etc.  ;  also  in  Kentucky,  Ohio,  Illinois,  Missouri,  and  Indiana ; 
but  part  of  the  so-called  cannel  is  a  coaly  shale. 

Brown  coal  comes  from  coal  beds  more  recent  than  those  of  the  Carboniferous  age.  But 
much  of  this  more  recent  coal  is  not  distinguishable  from  other  bituminous  coals.  The  coal 
of  Richmond,  Virginia,  is  supposed  to  be  of  the  Liassic  or  Triassic  era ;  the  coal  of  Brora,  in 
Sutherland,  and  of  Bovey,  Yorkshire,  is  Oolitic  in  age.  Cretaceous  coal  occurs  on  Van- 
couver Island,  and  Cretaceous  and  Tertiary  coal  in  many  places  over  the  Rocky  Mountains, 
where  a  ' '  Lignitic  formation  "  is  very  widely  distributed. 


APPENDIX   A. 


SYNOPSIS  OF  MILLER'S  SYSTEM  OF  CRYSTALLOGRAPHY. 


THE  following  pages  contain  a  concise  presentation  of  the  System  of  Crystallography  pro- 
posed by  Prof.  W.  H.  Miller  in  1839,  and  now  employed  by  a  large  proportion  of  the  workers 
in  Mineralogy.  The  attempt  has  been  made  to  present  the  subject  briefly,  and  yet  with  suffi- 
cient fulness  to  enable  any  one  having  some  previous  knowledge  of  Crystallography  not  only 
to  understand  the  System,  but  also  to  use  it  himself.  For  the  full  development  of  the  subject, 
especially  of  its  theoretical  side,  reference  must  be  made  to  the  works  of  Miller,  Grailich, 
von  Lang,  and  Schrauf ,  referred  to  in  the  Introduction,  as  also  to  the  admirable  Lectures  of 
Prof.  Maskelyne,  printed  in  the  Chemical  News  for  1873  (vol.  xxxi.,  3,  13,  24,  63,  101,  111, 
121,  153,  200,.  232). 


GENERAL  PRINCIPLES. 

The  indices  of  Miller  and  their  relation  to  those  of  Naumann. — The  position  of  a  plane  ABC 
(f.  751)  is  determined  when  the  distances  OA,  OB,  OC  are  known,  which  it  cuts  off  in  the 

751 


assumed  axes  X,  Y,  Z  from  their  point  of  intersection  0.  The  lengths  of  these  axes  for  a 
single  plane  of  a  crystal  being  taken  as  units,  thus  OA  =  «,  OB  =  b,  OC  —  c,  it  is  found  that  the 
lengths  of  the  corresponding  lines  OH,  OK,  OL  for  any  other  plane,  HKL,  of  the  same  crys- 


400 


APPENDIX. 


tal  always  bear  some  simple  relation,  expressed  in  whole  numbers,  to  these  assumed  units. 
This  relation  may  be  expressed  as  follows  : 


OH 
or  in  the  more  common  form 


b 
OK 


a 
OH 


_ 
*. 


b 
OK 


QL 


c 
OL 


(1) 


The  numbers  represented  by  /£,  #,  I  are  called  the  indices  of  the  plane  and  determine  its 
position,  when  the  elements  of  the  crystal — the  lengths  and  mutual  inclinations  of  the  axes — 
are  known.  When  the  lines  are  taken  in  the  opposite  direction  from  O,  they  are  called  nega- 
tive ;  the  corresponding  negative  character  of  the  indices  is  indicated  by  the  minus  sign 
placed  over  the  index,  thus,  A,  k,  or  I.  When  the  unit,  or  fundamental  form,  is  appropriately 
chosen,  the  numbers  representing  A,  &,  I  seldom  exceed  six. 

The  above  relation  may  also  be  written  in  the  form  : 


OH 


—  r 


OK 

b 


OL 


=  m. 


Here  ?',  n,  m,  which  are  obviously  the  reciprocals  of  the  indices  h,  k,  I  respectively,  are 
essentially  identical  with  the  symbols  of  Naumann.  For  example,  if  h  =  3,  k  =  2,  I  =  2, 
then  r  =  £,  n  —  •£,  m  =  •£,  and  the  symbol  (322)  of  Miller  becomes  ^a  :  $b  :  $s-  but  by  Nau- 
mann's  usage  this  is  so  transformed  that  r  =  1,  and  n  >  1  (or  sometimes  n  =  1,  and  r  >  1), 
in  other  words,  by  multiplying  through  by  3,  in  this  case,  the  symbol  takes  the  form  a  :  *b  : 
%c,*  or,  as  abbreviated,  £-f  (?Pf).  The  symbol  a  :  |&  :  fc  properly  belongs  to  the  plane  MNR 
(f.  751),  which  is  parallel  to,  and  hence  crystallographically  identical  (p.  11)  with  the  plane 
HKL. 

Special  values  of  the  indices  h,  k,  I.  It  is  obvious  that  several  distinct  cases  are  possible  : 
(1)  The  three  indices  7i,  &,  I  are  all  greater  than  unity,  then  including  the  various  pyramidal 


planes.     The  number  of  similar  planes  corresponding  to  the  general  form  j  hkl  I  depends 

upon  the  degree  of  symmetry  of  the  crystalline  system,  and  upon  the  special  values  of  h,  k,  I, 
e.g.,  h  —  k,  etc.     These  cases  are  considered  later  in  their  proper  place. 

(2)  One  of  the  three  indices  may  be  equal  to  zero,  indicating  then  that  the  plane  is  parallel 
to  the  axis  corresponding  to  this  index.  Thus  the  symbol  (MO),  =  a  :  nb  :  oo  4,  or  na  :  b  :  GO  c 
(p.  11),  belongs  to  the  planes  parallel  to  the  vertical  axis  r,  as  shown  in  f.  752.  They  are 
called  prismatic  planes.  The  symbol  (hQl),  =  a  :  <x>b  :  me  (p.  11)  belongs  to  the  planes  par- 
allel to  the  axis  b,  as  in  f.  753.  The  symbol  (Okl),  •—  oo  a  :  b  :  me,  belongs  to  the  planes  parallel 
to  the  axis  a,  f.  754. 


752 


753 


M-0 


755 


001 


(3)  Two  of  the  indices  may  be  zero,  the  symbol  (7tM)  then  becomes  (001),  =  oo«  :  oo5  :  c, 
the  basal  plane,  f.  755  ;  (010),  =  ooa  :  b  :  OOP;  and  (100),  =  a  :  <x>b  :  ooc.  These  are  the 
three  diametral  or  pinacoid  planes. 

The  symbol  (010)  represents  the  clinojnnacmd  (£-%)  of  the  Monoclinic  system,  but  (following 
Miller)  the  macropinacoid  (i-l)  of  the  Orthorhombic.  Similarly  (hOf)  belongs  to  the  ortho- 


*  The  symbol  is  written  here  in  this  order  to  correspond  with  the  (7t  k  I)  of  Miller ;  on 
page  10,  and  subsequently,  the  reverse  order  f  e  :  f  b  :  a  was  adopted  for  the  sake  of  uni- 
formity with  Naumann' s  abbreviated  symbols. 


MILLER  S    SYSTEM   OF    CRYSTALLOGRAPHY. 


401 


domes  of  the  Monoclinic,  but  the  bracliydomes  of  the  Orthorhombic  system  ;  also  (OM)  belongs 
to  the  clinodomes  of  the  former,  and  the  macrodomes  of  the  latter.     See  also  p.  415. 

Spherical  Projection. — If  the  centre  of  a  crystal,  that  is,  the  point  of  intersection  of  the 
three  axes,  be  taken  as  the  centre  of  a 
sphere,  and  normals  be  drawn  from  it  to 
the  successive  planes  of  the  crystals,  the 
points,  where  they  meet  the  surface  of  the 
sphere,  will  be  the  poles  of  the  respective 
planes.  For  example,  in  f.  756  the  com- 
mon centre  of  the  crystal  and  sphere  is  at  O, 
the  normal  to  the  plane  b  meets  the  surface 
of  the  sphere  at  B,  of  b'  at  B',  of  d  and  e 
at  D  and  E  respectively,  and  so  on.  These 
poles  evidently  determine  the  position  of 
the  plane  in  each  case. 

It  is  obvious  that  the  pole  of  the  plane  b' 
(010)  opposite  b  (010),  will  be  at  the  oppo- 
site  extremity  of  the  diameter  of  the  sphere, 
and  so  in  general,  (120)  and  (120),  etc.  It  is 
seen  also  that  all  the  poles,  or  normal  points, 
of  planes  in  the  same  zone,  that  is,  planes 
whose  intersection-lines  are  parallel,  are  in 
the  same  great  circle,  for  instance  the 
planes  b  (010),  d  (110),  a  (100),  c  (110),  and 
so  on. 

It  is  customary*  in  the  use  of  the  sphere 
to  regard  it  as  projected  upon  a  horizontal 
plane,  usually  that  normal  to  the  prismatic 
zone,  so  that,  as  in  f .  759,  the  prismatic  planes  lie  in  the  circumference  of  the  circle,  and  the 
other  planes  within  it.  The  eye  being  supposed  to  be  situated  at  the  opposite  extremity  of 
the  diameter  of  the  sphere  normal  to  this  plane,  the  great  circles  then  appear  either  as  arcs 
of  circles,  or  as  straight  lines,  i.e.,  diameters. 

It  will  be  further  obvious  from  f.  750  that  the  arc  BD,  between  the  poles  of  b  and  d,  mea- 
sures an  angle  at  the  centre  (BOD),  which  is  the  supplement  of  the  actual  interior  angle  bnd 
between  the  two  planes.  This  fact,  that  the  arc  of  a  great  circle  intercepted  between  the 
poles  of  two  planes  always  gives  the  supplement  of  the  actual  angle  between  the  planes  them- 
selves, is  most  important,  and  does  much  to  facilitate  the  ease  of  calculation.  In  consequence 
of  this,  it  is  customary  with  many  crystallographers  to  give  for  the  angle  between  two  planes, 
not  the  interfacial  angle,  but  that  between  their  normals. 

It  is  one  of  the  great  advantages  of  this  method  of  projection  that  it  may  be  employed  to 
show  not  only  the  relative  positions  of  the  planes,  but  also  those  of  the  optic  axes,  and  the 
axes  of  elasticity. 

Relation  between  the  indices  of  a  plane  and  the  angle  made  by  it  with  the  axes  — When  the 
assumed  axes  are  at  right  angles  to  each  other  they  coincide 
with  the  normals  to  the  piuacoid  planes  (001,  010,  100),  and 
consequently  meet  the  spherical  surface  at  their  poles.  When 
the  axial  angles  are  not  90°,  this  is  no  longer  true.  In  all 
cases,  however,  the  following  relation  holds  good  between 
the  cosines  of  the  angles  made  by  a  plane  with  the  axes : 


But  from  the  equation  (1)  before  given,  by  the  introduction 
of  the  values  of  OH,  OK,  OL,  we  obtain  : 


4-  cos  PX  =  ~  cos  PY  =  4-  cos  PZ. 
h  k  I 


(2) 


This  equation  is  fundamental,  and  many  of  the  relations  given  beyond  are  deduced  from  it. 
It  will  be  seen  that  in  the  case  of  the  orthometric  systems  the  angles  PX,  PY,  PZ  are  the 
supplement-angles  between  any  plane  (hkl)  and  the  pinacoids  (001),  (010),  (100). 

Relations  between  planes  in  the  same  zone. — By  the  use  of  the  equation  (2),  it  may  be  shown 


*  On  the  construction  of  the  spherical  projection,  see  p.  58. 


402 


APPENDIX. 


that  if  two  planes  (hkl)  and  (pqr)  lie  in  the  same  zone,  that  the  following  equation  must  hold 
good  : 

ua  cos  XQ  +  vb  cos  YQ  +  we  cos  ZQ  =  0, 


where 


u  =  kr  —  Iq,        v  —  Ip  —  hr,        w  =  hq  —  kp. 


The  letters  u,  v,  w  are  called  the  symbol  of  the  zone  or  great  circle  PR. 
~R,(xyz)  of  this  zone  must  satisfy  the  equation  : 


+ 


Every  plane 


(3) 


If  now  (uvw)  be  the  symbol  of  one  zone,  and  (efg)  of  another  intersecting  it,  then  the  point 
of  intersection  will  be  the  pole  of  a  plane  lying  in.  both  zones,  whose  indices  (hid)  must  satisfy 
two  equations  similar  to  (3).  These  indices  are  equal  to : 


h  =  gv  —  f  w 


k  =  ew  —  gu 


I  =  f  u  -  ev. 


The  application  of  this  principle  is  extremely  simple,  and  its  importance  cannot  be  over- 
estimated. Some  examples  are  added  here,  showing  the  method  of  use. 

Examples  of  the  methods  of  calculation  by  zones. — (1)  For  the  zone  of  planes  between  (100) 
and  (001),  the  zone  indices  are  u  =  0,  v  =  —  1,  w  =  0.  They  are  obtained  by  multiplication 
in  the  manner  indicated  in  the  following  scheme  : 


In  general 


h        k       I 


In  this  case 


0         0 


0 


=  kr 


p        q       r       p        q 

•  lq  ;  v  =  Ip  —  hr  ;  w  =  hq  —  kp. 


001 
u  =  0;  v  = 


XXX 


0        0 
w  =  0. 


Consequently  every  plane  (hkl]  in  the  zone  named  must  answer  the  condition :  u7i  +  v£ 
-f-  wl  =  0,  that  is,  in  this  case  k  —  0.  The  general  symbol  is  consequently  (hQl).  Compare 
f.  759. 

00100 


(2)  For  the  zone  (001),  (010),  in  a  similar  manner: 


1 


0 


u  =  1,  v  =  0,  w  =  0,  and  the  equation  of  condition  becomes  h  =  0,  and  the  general  sym- 
bol is  (07^).    Compare  f.  759. 

(3)  For  the  prismatic  zone  between  (100)  and  (010),  the  general  symbol  will  be  found  to  be 
(MO).     Compare  f.  759. 
(4)  For  the  pyramidal  zone  between  the  basal  plane  (001)  and 

00100 

.XX 

o      i      1 


the  unit  prism  (110),  we  have  the  scheme  : 

1         1 
I  Hence  n  =  1,  v  =  1,  w  =  0,  and  the   equation   of 


In  general        u        v 


condition  be- 
comes h  =  k,  and  hence  the  general  symbol  is  hhl  for  the  unit  pyra- 
mids. 

For  a  plane  lying  at  once  in  two  zones,  for  instance  the  plane 
lettered  2-2  in  f.  758,  lying  in  the  zone  7,  2-2,  l-£,  and  in  the  zone 
i-l,  3-3,  2-2,  1,  1-1.  The  indices,  uvw,  for  the  first  zone  l-£  (101), 
1  (110),  are,  obtained  as  above,  u  =  1,  v  =  1,  w  =  1.  Again,  for 
the  zone  between  i-i  (100),  1-1  (Oil),  the  zone  indices,  efg,  are, 
e  =  0,  f  =  l,  g  =  l.  The  indices  (hkl],  for  the  plane  (2-2)  lying  in 
both  these  zones,  and  hence  answering  to  two  equations  of  condi- 
tion, are  -obtained  by  multiplication  in  a  scheme  exactly  like  that 
already  given,  viz.  : 

111 


u        v         In  this  case        1 

XXX  _XXX. 

efgef  01101 

h  =  gv  —  f  w  ;  k  =  ew  —  gu ;  I  =  fu  —  ev.  h  =  2 ;  k  =  1 ;  I  =  1. 

The  plane  has  consequently  the  symbol  (211). 


MILLER'S  SYSTEM  OF  CRYSTALLOGRAPHY. 


403 


For  the  zone  of  planes,  lettered  on  the  figure  (f.  758)  i-i,  3-3,  2-2,  etc.,  the  indices,  as 
already  shown,  are  e  =  0,  f  =  1.'  g  =  1, 

and  consequently  the  equation  of  condi-  759 

tion  reduces  to  k  =  I,  and  the  general 
symbol  is  hkk.  This  zone  is  shown  on  the 
sphei'ical  projection,  f.  759,  and  includes 
the  planes  100  (i-i),  311  (3-3),  211  (2-5), 
111  (1),  Oil  (1-S),  and  so  on. 

A  second  example  of  the  above  method 
is  afforded  by  the  plane  lettered  2-2  in 
f .  758.  It  lies  in  the  zone  i-l  (010)  to  \-i 
(101),  whose  indices,  uvw,  obtained  as  be- 
fore, are,  u  —  1,  v  =  0,  w  =  1.  It  is  also 
in  the  zone  between  7(110)  and  l_-l  (Oil), 
whose  indices,  efg,  are,  e  =1,  f  —  1,  g  =  1. 
Its  own  symbol  (hkl)  is  deduced  as  above  : 


0 


0 


11111 

h  =  1 ;  k  =  2  ;  I  =  1. 

The  symbol  is  consequently  (121).    The 
position  of  this  plane  is  shown   on   the 

spherical  projection,  f.  759,  as  also  that  of  the  zone  first  mentioned  above,  whose  indices  were 
u  =  1,  v  =  0.  w  —  1,  and  for  which  the  equation  (3)  consequently  reduces  to  h  =  I ;  the  gen- 
eral symbol  is  then  (JMi),  the  planes  010  (t-i),  121  (2-2),  111  (1),  101  (1-2),  etc.,  belong  in  this 
zone. 

The  example  employed  here  serves  to  show  the  extensive  application  of  this  principle  of 
zones.  Supposing  that  in  this  crystal,  f.  758,  1  (110),  and  1-2  (101)  have  been  assumed  as 
fundamental  planes  in  their  respective  zones,  the  symbols  of  all  the  others  may  be  obtained  in 
this  way,  without  the  necessity  of  a  single  measurement ;  the  reflective  gonometer  would 
indicate  the  presence  of  the  few  necessary  zones  not  shown  by  the  parallel  intersections. 

Methods  of  Calculation. — In  consequence  of  the  wide  application  of  this  method  of  deter- 
mining the  symbols  of  a  plane  by  the  zones  in  which  it  lies,  actual  trigonometrical  calcula- 
tions are  not  very  frequently  required.  The  methods  employed  are  always  those  of  spherical 
trigonometry,  and  in  most  cases  no  formulas  are  needed,  the  problems  arising  requiring 
nothing  but  the  solution  of  the  triangles,  mostly  right-angled,  seen  on  the  spherical  projection. 
It  is  to  be  remembered  that  an  arc  of  a  great  circle,  between  two  poles,  shown  in  the  projec- 
tion, is  always  the  supplement  of  the  actual  interf  acial  angle  between  the  planes  themselves. 

Some  of  the  more  commonly  used  formulas  for  the  solution  of  spherical  triangles,  which 
have  been  already  given  on  p  02,  are,  for  the  sake  of  convenience,  repeated  here. 
In  right-angled  spherical  triangles  C  =  90°,  h  =  the  hypothenuse. 


Sin  A  = 


Cos  A  = 


sin  h 
tan  b 
tan/i 


tan  a 

Tan  A  =  -7—= 
sin  b 

cos  B 

Sin  A  = =• 

cos  b 


sin  b 
sin  B  =  ^- 


cos  B  = 


tan  B  = 


tan  a 
tan  h 
tan  b 
sin  a 


.  cos  A 

sin  B  =  — 

cos  a 


cos  h  =  cos  a  cos  b 
cos  li  =  cot  A  cot  B 


In  oblique-angled  spherical  triangles  : 


(1)  Sin  A  :  sin  B  =  sin  a  :  sin  b ; 

(2)  Cos  a  =  cos  b  cos  c  +  sin  b  sin  c  cos  A  ; 

(3)  Cot  b  sin  c  =  cos  c  cos  A  +  sin  A  cot  B ; 

(4)  Cos  A  =  —  cos  B  cos  C  +  sin  B  sin  C  cos  a. 


4:04  APPENDIX. 

In  calculation  it  is  often  more  convenient  to  use,  instead  of  the  latter  formulas,  those 
especially  arranged  for  logarithms,  which  will  be  found  in  any  of  the  many  books  devoted 
to  mathematical  formulas. 

In  addition  to  the  mere  solution  of  triangles  on  the  spherical  projection,  it  is  also  necessary 
to  connect  by  equations  the  actually  measured  angles  with  the  lengths  and  inclinations  of 
axes  of  the  crystals  themselves.  These  equations  are  given  in  connection  with  the  different 
systems. 

The  following  relation  between  the  planes  in  the  same  zone  is  also  of  very  wide  appli- 
cation : 

Let  P,  Q,  S,  R  be  the  poles  of  four  planes  in  a  zone  (f.  760),  having  the  following  indices, 
viz.  :  P  =  (hkl),  Q  =  (pqr),  R  =  (uvw),  S  =  (xyz).    The  folowing  relation  may 
760  be  deduced  between  them,  on  the  supposition  that  PQ  <  PR. 

cot  PS  -  cot  PR  _   (P.Q)       (S.R) 
cot  PQ  -  cot  PR  ~~  TQll)   '    (P.S)  * 

H  r  (P.Q)   _  kr  —  lq  _  Ip  —  7ir  _  Jig  —  kp 

(Q.R)       qw  —  rv      ru—pw     pv  —  qu1 

(S.R)  _  wy  —  zv  _  zu  —  xw  _xv  —yu 
"(PTS)"  ~  kz  -  ly  ~  Ix-hs  ~  hy  -  kx      ' 

By  means  of  the  above  equation  it  is  possible  to  deduce  the  indices  or  angle  of  a  fourth 
plane,  when  those  of  the  three  others  are  given.  In  the  application  of  this  principle  it  is 
essential  that  the  planes  should  be  taken  in  the  proper  order,  as  shown  above  ;  to  accomplish 
this  it  is  often  necessary  to  use  the  indices  and  corresponding  angles,  not  of  (hkl),  but  its 
opposite  plane  (/;!•/),  etc. 

In  the  orthometric  systems  this  relation  admits  of  being  much  simplified. 

If  one  of  the  above  four  planes  coincides  with  a  pinacoid  plane  (100),  (010),  or  (001),  and 
another  with  a  plane  in  a  zone  with  a  second  pinacoid  90°  from  the  first,  then  the  following 
relations  hold  good  for  two  planes  ~P(hkl),  and  Q(pqr)  in  this  zone  : 

h    tan  PA  _  k  =  I 
p  '  tan  QA  "~  q  ~  r ' 

h       k    tan  PB      I 


p       q  '  tan  QB      ?-' 

h_k_l_     tan  PC 
p~  q  ~  r  '  tan  QC' 

As  a  further  simplification  of  the  above  equation  for  the  case  of  a  prismatic  plane  (7*&0),  or 
a  dome  (hOl)  or  (OAtf),  between  two  pinacoid  planes  90°  from  another,  we  have  : 

7i  _  tan  (100)  (110)  e          7i  _  tan  (001)  (hW) .         _*  _  tan  (001)  (OH) 
Ic  ~  tan  (100)  (Jikff) '         T  ~  tan  (001)  (101) '  I  ~  tan  (001)  (Oil)' 

These  equations  are  the  ones  ordinarily  employed  to  determine  the  symbol  of  any  prismatic 
plane  or  dome.  It  will  be  seen  at  once  that  all  the  above  relations  for  rectangular  zones  are 
essentially  identical  with  those  given  on  p.  59,  though  here  expressed  in  a  clearer  and  more 
concise  form. 

SYSTEMS  OF  CRYSTALLIZATION. 

All  crystals  are  divided  into  six  classes,  according  to  the  degree  of  symmetry  which  charac- 
terizes them.  This  symmetry,  as  well  as  the  relations  of  the  different  planes  of  a  crystal,  is 
shown  in  the  lengths  and  position  of  the  axes  which  are  taken  for  each.  With  reference  to 
their  axial  relations  crystals  are  divided  into  the  following  six  systems  : 

I.  Isometric  System, — Three  equal  axes  (a,  a,  a)  at  right  angles  to  one  another. 

II.  Tetragonal  System.— Two  equal  lateral  axes  (a,  a),  and  a  third  vertical  axis  (c)  of  un- 
equal length ;  all  at  right  angles. 


MILLER'S  SYSTEM  OF  CRYSTALLOGRAPHY. 


405 


III.  Hexagonal  System. — Three  equal  lateral  axes  (a,  «,  a)  crossing  at  angles  of  60°,  and  a 
fourth  vertical  axis  (c)  of  unequal  length,  perpendicular  to  the  plane  of  the  others. 

IV.  Oftkorhombw  System.  — Three  unequal  axes  (c,  6,  a)  at  right  angles  to  each  other. 

V.  MonodimG  System, — Three  unequal   axes  (c,  #,  d) ;    the   angle  between   c   and  £,  aiid 
between  b  and  d  =  90%  but  the  angle  between  c  and  d  greater  and  less  than  90°. 

VI.  Tridinie  System. — Three  unequal  axes  (c,  £,  a)  ;  the  axial  angles  a,  /?,  y  all  oblique. 


I.  ISOMETRIC  SYSTEM. 

The  symbol  [hkl]  embraces  all  the  forms  possible  under  each  system  in  the  most  general 
case.  Since  in  the  Isometric  System  all  the  axes  are  of  equal  value,  it  obviously  follows 
from  the  symmetry  of  the  system  that  each  one  of  the  indices  may  be  exchanged  for  each  of 
the  others,  so  that  the  total  number  of  planes  possible  will  be  given  by  all  the  arrangements 
of  the  indices  ±h,  ±&,  ±Z,  or  as  follows: 


Tiki 
Ml 
hkl 
hkl 
hkl 
hkl 
hkl 
hkl 


hlk 
hlk 
hlk 
hlk 
hlk 
hlk 
hlk 


khl 
khl 
khl 
khl 
khl 
hhl 
khl 
khl 


klh 
klh 
klh 
klh 
klh 
klh 
klh 
klh 


Ihk 
Ihk 
Ihk 
Ihk 
Ihk 
Ihk 
Ihh 
Ihk 


Ikh 
Ikh 
Ikh 
Ikh 
Ikh 
Ikh 
Ikh 
Ikh 


A.  Holohedral  Forms. 

There  are  seven  cases  possible  among  the  holohedral  forms  of  this  system,  according  to  the 
values  of  h,  k,  I.  These  are  shown  in  the  list  below,  to  which  are  added  the  symbols,  after 
Naumann,  given  on  p.  14,  though,  as  already  explained,  written  in  the  inverse  order.  In  the 
most  general  case  [hkl]*  the  form  includes  forty-eight  similar  planes,  and  in  the  most 
special  case  [100],  there  are  included  six  similar  planes. 


MILLER. 

1.  [hkl]  ;  h>k>l. 
2..[hkk];  h>k. 

3.  [hhk]  ;  h>k. 

4.  [Ill]  ;  h  =  k  =  l  =  l. 

5.  [hkO]  -,l  =  0. 

6.  [110]  ;  h  =  k  =  1  ;  I  =  0. 

7.  [100]  ;  h  =  1,  *  =  I  =  0. 


NAUMANN. 
na  :  ma 
ma  :  ma 
a  :  ma 
a  :  a 
na  :  cca 
a  :  ooa 
<x>a  :  <x>a 


[m-n]t 
[m-m]. 
[m].  ' 
[I]. 

[<£" 

[#]. 


The  seven  distinct  forms  corresponding  to  these  symbols  are  as  follows,  taken  in  the  same 
order  as  on  pp  14-20,  where  the  forms  are  described  : 

Cube  (f.  761).— Symbol  [100],  including  the  six  planes  (100),  (010),  (100),  (010),  (001), 
(001).  See  also  the  spherical  projection  (f.  766). 

761  762  763  764 


[100]  [111]  [110]  [100]  [111]  [100]  [110]  [111] 

Octahedron  _(f.  762^ — Symbol  [11 1],  Jncluding  the^ eight  planes  taken  in  order  shown  in 
f.  762,  (111),  (111),  (111),  (111),  (111),  (111),  (111),  (111). 

*In  general  the  indices  of  any  individual  plane  are  written  (hkl),  whereas  the  general 
symbol  [hid]  indicates  all  the  planes  belonging  to  the  form,  varying  in  number  in  the  different 
systems  ;  thus,  in  this  system,  [100]  is  the  general  symbol  for  the  six  similar  planes  of  the 
cube. 


406 


APPENDIX. 


Dodecahedron  (f.  763).— Symbol  [110],  including  the   twelve  planes,  (110),    (110) 
(110),  (101),  (Oil),  (101),  (Oil),  (101),  (Oil),  (101),  (Oil). 

The  relations  between  these  three  forms  are  given  in  full  on  pp.  15,  16,  and  need  not  be 
repeated.  It  is  to  be  noticed  that  the  distance  between  two  contiguous  poles  of  [100J  and 
[110]  is  45°  (see  f.  766) ;  between  those  of  [100]  and  [111]  it  is  54°  44',  and  between  (tlO)  and 
(111)  it  is  35°  16'.  Moreover,  the  angle  between  (111)  and  (111)  is  70°  32',  and  between  (111) 
and  (111),  109°  28'. 


766 


767 


[211] 


[3111 

^  Tetragonal  trisoctaJiedron  (f.  767,  768). — Symbol  [Jtkk],  with  h>k,  comprising  twenty-four 
similar  planes. 

Trigonal  trisoctahedron  (f.  769). — Symbol  [hhk],  with/i>&,  also  embracing  twenty-four  like 
planes. 


771 


772 


[210] 


[310] 


[321] 


TetraliexaJiedron  (f.  770.  771). — Symbol  [7ikQ\  including  twenty-four  like  planes.  As  seen  on 
the  spherical  projection  (f.  766),  the  planes  of  the  form  [7i&0]  lie  in  a  zone  with  the  dodeca- 
hedral  planes,  between  two  pinacoid  planes. 

Hexoctahedron  (f.  772),  [hkl], — This  is  the  most  general  form  in  the  system,  including  the 
forty-eight  planes  enumerated  on  p.  405.  Their  position  (h  =  3,  k  =  2,  I  =  1)  is  shown  on 
the  spherical  projection  (f.  766). 


B.  Hemihedrol  Forms. 

There  are  two  kinds  of  hemihedral  forms  observed,  as  shown  on  p.  20:  (1)  the  holohemi- 
Tiedral,  where  half  the  quadrants  have  the  whole  number  of  planes ;  and  (2)  the  holohemihedral 
where  all  the  quadrants  have  half  the  full  number  of  planes.  The  first  kind  produces  inclined 
'hemihedrons,  indicated  by  the  symbol  K[hM],  and  the  second  kind  produces  parallel  hemihe- 
drons,  indicated  by  the  symbol  ir[hkl\.  The  resulting  forms  in  the  several  cases  are  as  follows  : 


MILLER  S  SYSTEM  OF  CRYSTALLOGRAPHY. 


407 


INCLINED  HEMIHEDRISM. — Tetrahedron,  (±1).  _  Symbol  «[!!!].  The  plus  tetrahedron 
(f  773)  includes  the  four  planes  (111),  (III),  (111),  (HI).  The  minus  tetrahedon  (f.  774) 
includes  the  planes  (111),  (111),  (111),  (111). 


773 


774 


775 


776 


4111] 


/c[321] 


Hemi-trisoctahedrons. — The  symbol  n[hkk\  denotes  the  solid  shown  in  f.  775,  and  K[h7ik\ 
the  solid  shown  in  f .  776.  They  are  the  hemihedral  forms  of  the  tetragonal  and  trigonal 
trisoctahedrons  respectively. 

Hemi-hexoctaJiedron. — The  same  kind  of  hemihedrism  applied  to  the  hexoctahedron  pro- 
duces the  form  shown  in  f.  777,  having  the  general  symbol  K\JikX\. 

Inclined  hemihedrism  as  applied  to  the  three  other  solids  of  this  system  produces  forms 
in  no  way  different,  in  outward  appearance,  from  the  holohedral  forms. 

PARALLEL  HEMIHEDRISM  produces  distinct,  independent,  forms  only  in  the  case  of  the 
tetrahexahedron  and  the  hexoctahedron.  The  symbol  of  the  former  is  7r[7i&0],  and  of  the 
latter,  n\Jik£\  ;  they  are  shown  in  f.  778-782. 


7T[210] 


7T[210] 


7T[120] 


-[210]  [100] 


7T[321] 


TetratoJiedral  forms  of  several  kinds  are  possible  in  this  system,  but  they  are  of  small 
piactical  interest. 

MatJiematical  Relations  of  the  Isometric  System. 

(1)  The  distance  of  the  pole  of  any  plane  P(hM)  from  the  cubic  (or  pinacoid)  planes  is  given 
by  the  following  equations.  These  are  derived  from  equation  (2),  p.  401.  Here  PX(=PA) 
is  the  distance  between  (hkl)  and  (100) ;  PY(— PB)  is  the  distance  between  (hkl)  and  (010) ; 
atd  PZ(— PC)  that  between  (hkl)  and  (001). 

The  following  equations  admit  of  much  simplification  in  special  cases,  for  (7i&0),  (Jihk),  etc. 


cos-  PA  = 


I* ' 


cos2  PB  = 


cos2  PC  = 


(2)  The  distance  between  the  poles  of  any  two  planes  (hkl)  and  (pqr)  is  given  by  the  fol- 
lowing equation,  which  in  special  cases  may  also  be  more  or  less  simplified  : 

po  _      hp  +  kg  +  IT 

^  -  V  (h*  +  &2  +  Z2)  (p*  +  q*  +  r2)' 

(3)  Calculation  of  the  values  of  ^,  &,  Z,  for  the  several  forms. — (a)  Tetragonal  trisoctahe- 
d)  on  (f .  767).     B  and  C  are  the  supplement  angles  of  the  edges  as  lettered  in  the  figure. 


cosB  = 


2hk 


408  APPENDIX. 

-  2A;2 


For  the  hemihedral  form  (f.  775),  cos  B  = 


2A;2' 


(b)  Trigonal  trisoctahedron.  —  The  angles  A  and  C  are,  as  before,  the  supplements  of  the 
interfacial  angles  of  the  edges  lettered  as  in  f.  769. 

A*  +  2hk 


For  the  hemihedral  form  (f.  776),  cos  B  =  ---  -  -  . 

Tetrahexahedron  (f.  770), 

h*  2hk 


_ 

For  the  hemihedral  form  (f.  778),  cos  A"  =  r  -  —  .  cos  C"  = 


+  k* 
Hexoctahedron  (f.  772). 


For  the  hemihedral  form  K  [/*&?]  (f.  777),  cos  B'  =  -*   ~  -  - 

ll    -{-  fC     +  6 

W  -  w  +  V  M  +  Ih  +  Ilk 

For  »[Wfl,  cos  A  =,  l  cos  C  = 


For  planes  lying  in  the  same  zone  the  methods  of  calculation  given  on  p.  402  and  p.  404 
are  made  use  of.  In  many  cases,  however,  the  simplest  method  of  solution  of  a  given  prob- 
lem is  by  means  of  the  spherical  triangles  on  the  projection  (f.  766). 

II.  TETRAGONAL  SYSTEM. 

In  the  Tetragonal  System,  since  the  vertical  axis  c  has  a  different  length  from  the  two 
equal  lateral  axes,  the  index  I,  referring  to  it,  is  never  exchangeable  for  the  other  indices,  h  and  k. 
The  general  form  \hkl\  consequently  embraces  all  the  planes  which  have  as  their  symbols 
the  different  arrangements  of  ±A,  ±&,  ±1,  in  which  I  always  holds  the  last  place.  We 
thus  obtain  : 

Tiki  Till  1M  hkl  Wil  Tchl  khl  kill 

Ml  likl  hkl  hkl  khl  khl  khl  khl 


A.  Holohedral  Forms. 

According  to  the  values  of  7^,  &,  and  I  in  this  general  form  (h  —  0,  k  =  h,  etc.),  different 
cases  may  arise.  By  this  means  we  obtain  a  list  of  all  the  possible  distinct  holohedral  forms 
in  this  system.  They  are  analogous  to  those  of  the  Isometric  System. 

MILLER.  NAUMANN. 


1.  [hkl]  ;  h>k. 

2.  [hhl]  -h  =  k. 

3.  [hOl]  ;  h  or  k  =  0. 


4.  [MO];  h>k,  1  = 

5.  [110]  ;..A  =  k  =  1,  1=0.  a 

6.  [100]  ;  k  =  0,  I  =  0.  a 


na  :  me  [m-n]* 

a  :  me  [m], 

oo  a  :  me  [m-i\. 

na  :  ooc  [i-n\t 


a  :  ooc 


oo  a  :  GO  c       [i-i] . 


7.  [001]  ;  h  =  k  =  Q.  <x>a:cca:c       \0]. 


MILLER  S    SYSTEM   OF   CRYSTALLOGRAPHY. 


409 


The  forms  answering  to  these  general  symbols  (compare  f.  790)  are  as  follows : 
Basal  planes.—  Symbol  [001],  including  the  planes  (001)  and  (001). 

Prism*. — (a)  Diametral  prism,  or_that  of  the  second  series  (L  783).  Symbol  [100],  in- 
cluding the  four  planes  (100),  (010),  (100),  (010). 

(b)  Unit  prism,  or  prism  of  the  first  series  (f.  784). — Symbol   [110],  embracing  the  four 
planes  (110),  (110),  (110),  (110).     The  relation  of  these  two  prisms  is  shown  on  p.  26. 

(c)  Octagonal  prism  (f.  785).  — Symbol  [MO],  including  the  eight  plaues  (MO),  (MO),  (MO), 
(MO),  (MO),  (MO),  (MO),  (MO). 

Octahedrons  or  Pyramids. — There  are  two  series  of  octahedral  planes,  corresponding  to  the 
two  square  prisms,  (a)  Octahedrons  of  the  second,  or  diametral  series.  Symbol  [hQl] ,  in- 
cluding eight  similar  planes.  The  form  [101]  is  shown  in  f.  786. 

(b)  Octahedrons  of  the  first,  or  unit  series. — Symbol  [hkl\ ,  embracing  eight  similar  planes. 
The  form  [111]  is  shown  in  f.  787. 

784 


[100]  [001] 


[110] 


[210] 


[101] 


[111] 


Octagonal  Pyramids. — The  general   symbol  [hkl\    embraces,  as    already  shown,  sixteen 
like  planes,  which  together  form  the  octagonal  pyramid  shown  in  f .  788. 


788 


789 


790 


Meionite. 


The  relations  of  the  various  tetragonal  forms  will  be  understood  by  reference  to  f.  790, 
showing  the  projection  for  the  crystal  represented  in  f.  789. 


B.  HemiJiedral  Forms. 

Among  the  hemihedral  forms  there  are  to  be  distinguished  three  classes, 
as  shown  on  p.  28  ct  seq.  1.  Sphenoidal  hemihedrons,  corresponding  to  the 
inclined  hemihedrons  of  the  isometric  system.  They  are  indicated  by  the 
symbol  K\hW>\.  The  sphenoid  7r[lll]  is  shown  in  f.  791. 

2.  Pyramidal  hemihedrons,  that  is,  those  which  are  hemiholohedral,  and 
vertically  direct.      These  are  indicated  by  the  symbol  K\hJtX\. 

3.  Trapezoidal  hemihedrons,  hemiholohedral  like  those  just  mentioned, 
but' vertically  alternate.     They  have  the  symbol  /c"[MZ]. 


791 


APPENDIX. 


Mathematical  Relations  of  the  Tetragonal  System. 

(1)  The  distances  of  the  pole  of  any  plane  P(hkl)  from  the  pinacoid  planes  100  (=  PA),  010 
(=  PB),  001  (=  PC)  are  given  by  the  following  equations: 


These  may  also  be  expressed  in  the  form  : 

WPA  =  *^,ta.PB 

(2)  For  the  distance  between  the  poles  of  any  two  planes  (hk£),  (pqr),  we  have  in  general  : 
cos  PQ  = 


The  above  equations  take  a  simpler  form  for  special  cases  often  occurring. 

(3)  Planes  in  the  same  zone.  —  For  the  general  case  of  planes  (hid}  and  (pqr)  the  re- 
lation given  in  equation  4  (p.  404)  is  made  use  of.  In  the  special  cases,  practically  of  the 
most  importance,  where  the  planes  lie  in  a  zone  with  a  pinacoid  plane,  the  simplified  formulas 
are  employed. 

For  the  octagonal  prism  this  relation  becomes  : 

tan  (100)  (MO)  =  cot  (010)  (hkO)  =  j  . 

Determination  of  the  axis  c.  —  This  follows  from  equation  (1),  p.  401,  which,  for  this  case, 
becomes  : 

^  cos  PA  =  -  cos  PC,  (a  =  1). 

For  an  octahedron  (hOt)  in  the  diametral  series,  we  have  : 

tan  (AOZ)  (001)  =  y. 

For  the  unit  octahedron  (111),  we  have  : 

tan  (111)  (001).  cos  45°  =  c. 

III.  HEXAGONAL  SYSTEM. 

The  Hexagonal  System  and  its  hemihedral,  or  rhombohedral,  division  are  both  included  by 
Miller  in  his  RHOMBOIIEDRAL  SYSTEM  (see  p.  420).  All  hexagonal  and  rhombohedral  forms 
are  referred  by  him  to  three  equal  axes,  oblique  to  one  another,  and  normal  to  the  faces  of 
the  unit  rhombohedron.  This  method  has  the  great  disadvantage  of  failing  to  exhibit  the 
hexagonal  symmetry  existing  in  the  holohedral  forms,  since  in  this  way  the  similar  planes  of  a 
hexagonal  pyramid  receive  two  different  sets  of  symbols,  having  no  apparent  connection  with 
each  other.  It,  moreover,  hides  the  relation  between  this  system  and  the  tetragonal  system, 
which,  optically,  are  identical,  since  they  possess  alike  one  axis  of  optical  symmetry. 

The  latter  difficulty  was  avoided  by  Schrauf,  who  introduced  the  ORTHO  HEXAGONAL  SYS- 
TEM. In  this  the  optical  axis  was  made  the  crystallographical  vertical  axis,  and  otherwise 
two  lateral  axes,  at  right  angles  to  each  other,  were  assumed,  a  and  a  t'3.  This  method,  how- 
ever, does  not  overcome  the  other  obj  ection  named  above. 

In  the  method  of  Weiss  and  Naumann  a  vertical  axis,  coinciding  with  the  optical  axis,  was 
adopted,  and  three  lateral  axes  in  a  plane  at  right  angles  to  it,  they  intersecting  at  angles  of 
60°,  corresponding  to  the  planes  of  symmetry  in  the  holohedral  forms  (see  p.  420).  In  this 
way  only  can  the  symmetry  of  the  hexagonal  forms  be  clearly  brought  out,  and  at  the  same 


MILLER  S    SYSTEM    OF   CRYSTALLOGRAPHY. 


411 


time  the  relation  between  the  hexagonal  and  tetragonal  systems  exhibited.  Kecently  Groth 
(Tsoh.  Min.  Mitth.,  1874,  223,  and  Phys.  Kryst.,  1876,  p.  252)  has  shown  that  the  complete 
symbols  of  Weiss  and  Naumann  could  be  translated  into  a  reciprocal,  integral  form  after 
the  manner  of  Miller.  The  symbols  then  obtained,  as  was  also  shown,  admit  of  a  like  con- 
venient use  in  calculation.  Essentially  the  same  method  was  proposed  in  1866  by  Bravais, 
and  his  suggestion  is  followed  here ;  the  more  important  equations,  expressing  the  relations 
between  the  poles  of  the  planes,  their  indices,  and  the  axes  of  the  crystal  are  also  added. 
They  are  given  somewhat  in  detail,  since  they  are  nofc  included  in  any  of  the  works  on  Miller's 
System  before  referred  to. 

All  hexagonal  forms  are  referred  to  a  vertical  axis,  c,  and  three  equal  lateral  axes  in  a 
plane  at  right  angles  to  it,  intersecting  at  angles  of  60° 

and  120°  (f.  792).     The  general  symbol  for  a  plane  in  this  793 

system  is  (hkli),  where  it  is  always  true  that  the  alge- 
braic sum  of  h,  k,  I  is  zero,  that  is,  h  +  k  +  I  =  0.  The 
indices  here  are  the  reciprocals  of  those  of  Naumann, 
except  that  the  index  I  has  the  opposite  sign,  and  the 
order  of  two  of  the  indices  is  inverted.  According  to 
him  the  general  symbol  of  any  plane  is  m-n  (=mPn), 


or,  in  full, — -  a  :  a  :  na  :  me. 


Thus  the  plane  3-f  (3Pf ) 


has  the  full  symbol,  3a  :  a  :  f  a  :  3c,  or  to  correspond 
with  the  other  symbols  it  must  be  written,  3a  :  fa  :  a  :  3c. 
The  reciprocals  of  the  latter  indices  are  i  :  £  :  1  :  i,  or, 
reduced  to  integers  (and  changing  the  sign  of  I)  (1231), 
which  is  the  symbol  according  to  the  plan  here  fol- 
lowed. Similarly  the  plane  (2243)  gives,  on  taking  the 
reciprocals,  \a  :  %a  :  %a  :  $c,  which  is  equivalent  to  2a  :  2a 
:  a  :  \c,  or  in  Naumann's  abbreviated  form  ^-2  (=^P2). 

It  is  the  great  advantage  of  this  method  that  it  makes  it  possible  to  change  the  almost  uni- 
versally adopted  symbols  of  Weiss  and 
Naumann  into  a  form  which  allow  of  all 
the  readiness  of  calculation  and  the  appli- 
cation to  the  spherical  projection  which 
are  the  characteristics  of  Miller's  System. 

In  calculations,  both  by  zone  equations 
and  other  methods,  only  two  of  the  indices 
h,  k,  or  I  of  the  form  (hkli)  need  be 
employed,  with  the  remaining  index  i  (re- 
ferring to  the  vertical  axis).  This  is  ob- 
viously true,  since  the  three  indices  named 
are  connected  by  the  equation  h  +  k  +  I 
—  0.  Disregarding,  then,  in  calculation 
the  third  index  £,  as  shown  beyond,  tbe 
planes  are  referred  to  two  equal  lateral 
axes,  intersecting  at  an  angle  of  120°, 
and  a  third  vertical  axis  c. 

The  symbol  [hkli]  in  its  more  gen- 
eral form  embraces  twenty-four  planes, 
as  is  evident  from  an  inspection  of  the 
spherical  projection,  f.  793.  Here  A,  k,  I 
are  of  equal  value  and  mutually  exchange- 
able, with  the  condition,  however,  that 
their  algebraic  sum  shall  always  equal 
zero.  Of  the  twenty -four  planes  of  the 

dihexagonal  pyramid,  the  following  are  those  of  the  upper  quadrants  mentioned  in  order 
from  left  to-right  around  the  circle  (f.  793).  Those  below  have  the  same  symbols,  except  that 
the  index  i  in  each  case  is  minus  : 


lib 


120 


(hkli) 
(hkli) 


(hlki) 
(hlki} 


(klhi) 
(klhi) 


(Ikhi) 
(Ikhi) 


(Ihki] 
(Ihki) 


(khli) 
(khh) 


In  this  general  form  {hkli]  the  following  special  cases  are  possible,  each  one  giving  rise 
to  an  independent  form  or  group  of  forms,  as  seen  below  : 


412 


APPENDIX. 


BKAVAIS-MlLLER. 


NATJMANN.* 


1. 

0  j  [7ih2h2i] 

2'  U1122]; 

3  j  [OA&]  ; 

3'  UOHl]; 

4.  [hkffi]  ; 

6.  [1120]  ; 

6.  [0110]  ; 

7.  [0001]  ; 


k  =  h  .  :  I  =  2h 

h  =  k  =  l  .-.  1  =  2,  i  = 

k  =  0  .  \  I  =  h 


i=0 


i  =  0,  k  =  0,  7i  =  l  .-.  1=1 
h  =  k  =  I  =  0. 


2a  :  2a  :  a  :  me 
2a  :  2a  :  a  :  c 
oo  a  :  a  :  a  :  me 
cca  :  a  :  a  :  c 

[m-2] 
[1-2] 
[m] 
[1] 

n 
—  T  a  :  na  :  a  :  oo  c 
n-\ 

[**] 

2a  :  2a  :  a  :  oo  c 

[i-2] 

co  a  :  a  :  a  :  co  c 

ffl 

oo  a  :  oo  a  :  oo  a  :  c 

[vl 

A.  Holohedral  Forms. 


The  forms  to  whicli  these  symbols  belong-  have  been  already  mentioned  on  pp.  32-34. 
They  may  be  briefly  recapitulated  here.  They  are  taken  in  the  reverse  order  from  that  given 
in  the  table. 

Basal  planes.—  Symbol  (0001)  and  (0001). 

Prisms.  —  (a)  The  unit  prism  (/).  General  symbol  [01  10],  including  (srje  f.  793.  794)  the 
six  planes  with  the  following  symbols:  (0110),  (1100),  (1010),  (0110),  (1100),  (1010). 

(b)  The   diagonal  prism  (i-2).      General  symbol  [1120],  including  (f.  793,  795)  the  follow- 
ing six  planes  :  (1120),  (1210),  (2110),  (1120),  (1210),  (2110). 

(c)  The  dihexagonal  prism  (i-n).     General  symbol  [hMQ],  embracing  the  following  twelve 
planes  mentioned  in  order  : 

(hm),  (MO),  (MO),  (MO),  (MO),  (MJO),  (MZO),  (7J&0),  (&7AO),  (ZMO),  (ZMO),  (M/0). 

Hexagonal  pyramids,  or  Quartzoids.  —  (a)  The  pyramids  of  the  first  or  unit  series.  General 
symbol  [Qhhi]  embracing  twelve_  similar  planes.  All  the  pyramids  of  this  series  lie  in  a 
zone  between  the  unit  prism  [0110]  and  the  base  [0001].  A  special  case  of  this  is  when 
h  =  k  =  i=l.  The  planes  of  this  form  (f.  796)  are  shown  on  the  projection,  f.  793. 


794 


795 


[0110] 


[1120] 


[0111] 


(b)  Pyramids  of  the  second,  or  diagonal  series.  General  symbol  [hh2h2i],  including  twelve 
planes,  analogous  to  those  of  the  pyramid  unit  series.  All  the  pyramids  of  this  series  lie  in 
a  zone  between  ^he  diagonal  prism,  whose  general  symbol  is  [1120],  and  the  basal  plane 
[0001]. 

Twelve-tided  pyramids,  or  Berylloids  (f.  997).— General  symbol  \?ikli\,  including  the  twenty- 
four  planes  enumerated  on  p.  411. 


*  The  order  of  the  terms  in  the  symbols  below  is  made  to  correspond  to  that  of  the  indices 


MILLER  S  SYSTEM  OF  CRYSTALLOGRAPHY. 


413 


798 


B.  Hemihedral  Forms. 

The  most  important  of  the  hemihedral  forms  in  this  system  are  as  follows  : 

1.  PYRAMIDAL  hemihedrism. — This  comes  under  the  head  of  holohemihedral  forms,  which 
are  vertically  direct  (see  pp.  34,  35).  It  is  indicated  like 

the  corresponding  hemihedrism  in  the  tetragonal  system 
it  [hkli].     It  is  common  on  apatite. 

2.  RHOMBOHEDRAL  hemihedrism. — These    included 
here  are  hemiholohedral,  and  vertically  alternate.     They 
are  indicated  in  general  by  K\hkH].    This  class  is  import- 
ant, since  it  embraces  the  RHOMBOHEDRAL  DIVISION. 

(a)  Rhombohedrons.  Symbol  ic[Qhhi] ;  the  unit,  or 
fundamental  rhombohedron  (+R,  f.  798)  has  the  svmbol 
ic [0111],  including_  the  six  planes:  (01 11),  (1011), 
(1101),  (1011),  (1101),  (0111).  The  negative  rhombohe- 
dron (— S^f.  799)  includes  the  planes:  (1101),  (0111), 
(1011),  (0111),  (1011),  (1101). 

(6)  Scalenohedrons  (f.  800).     Symbol  K\hkli\. 

3.  GYROIDAL,  or  trapezohedral  hemihedrism. — The 
forms  here  included  are  holohemihedral,  and  vertically 
alternate.     They  are  indicated  by  K"  [hkli]  ,  see  p.  39. 

4.  TETRATOHEDRISM. — This  may  be  (1)  rhombohedral, 

indicated  by  itir[hkU]  ;  or  (2)  traptzohedral  (gyroidal),  as  common  on  quartz,  having  the  gen- 
eral symbol  KK."[hkli]. 


Mathematical  Relations  of  the  Hexagonal  System. 

In  the  Hexagonal  System,  as  has  been  explained,  the  symbol  in  general  has  the  form 
[hkli].  where  the  algebraic  sum  of  A,  £,  and  I  is  zero.  This  general  symbol  has  four  in- 
dices, referring  respectively  to  the  three  equal  lateral  axes  and  the  vertical  axis,  as  shown 
in  f.  792,  thus  showing  the  fundamental  hexagonal  symmetry  of  the  forms.  Since,  however, 
the  position  of  a  plane  is  known  by  its  intersection  with  three  axes  aione,  two  of  the  three 
indices  7i,  &,  I  are  all  that  are  needed  in  calculation,  the  third,  I,  being  a  function,  as  given 
above,  of  h  and  k.  The  mathematical  relations  of  the  planes  in  this  system  are  brought  out  by 
referring  them  to  three  axes,  viz.,  two  equal  lateral  axes  H,  K,  (=«  =  !)  oblique  (120°  and 
60°)  to  one  another,  and  a  third  axis  (c)  of  unequal  length  perpendicular  to  their  plane. 

This  applies  also  to  the  calculation  by  zonal  equations.  The  indices  (u,  v,  w)  of  the  zone 
in  which  the  planes  (hkli] ,  (pqrt)  lie,  are  given  by  the  scheme  : 


h        k 


k 


u  =  kt 


XXX 

p        q         t        p         q 

qi      v  =  ip  —  ht  w 


=  hq  —  kp. 


(1)  The  distances  (see  f .  793)  of  the  pole  of  any  plane  (hkli)  from  the  poles  of  the  planes 
(1010),  (0110),  (1100),  and  (0001)  are  given  by  the  following  equations: 


cos  PA  =  cos  (hkli)  (1010)  = 


c(2h  +  k) 


cos  PB  =  cos  (AW)  (0110)  = 


cos  PM  =  cos  (MO  (1100)  = 


cos  PC  =  co8  (UK)  (0001)  = 


414:  APPENDIX. 

(2)  The  distance  (PQ)  between  the  poles  of  any  two  planes  (JiTdi)  and  (  pqrt}  is  given  by  the 
equation  : 


OOB  po  =       __  _ 

V  [3^  +  4<w(#i  + 

(8)  For  special  cases  the  above  formula  becomes  simplified  ;  it  serves  to  give  the  value  of 
the  normal  angles  for  the  several  forms  in  the  system.     They  are  as  follows  : 
(a)  Hexagonal  Pyramid  [OM£],  f.  796, 


cos  X  (terminal)  =  ^ j--^ 

For  the  hexagonal  pyramids  of  the  second  series  [07*2A24*]  the  angles  have  the  same  value. 
(b)  Dihexagonal  Pyramid  [hkli  ] , 

cos  X  (see  f.  797)  =  f 
o 

cos  Y  (see  f .  797)  =  %7  ~4^ 


hk)  -  3«2 
cos  Z  (basal)         =  __1_:_  __fc_. 


(c)  Dihexagonal  Prism  [M/0], 


cos  X  (axial)        = 


+  k*  +  hk) ' 


2k*  +  2hk  -  K 
cos  Y  (diagonal)  =  ^—^—^ 

(d)  Rhombohedron  /c[OM/], 

..       3*2-27i2c2 
cos  X  (terminal)  =  -_-. 

(e)  Scalenohedron  K[hk1i\t 


r7/U  U 

cos  Z  (basal)  =  _ 

(4)  Relations  of  planes  in  a  zone.—  The  general  equation  (3,  p.  404)  is  to  be  employed. 
For  the  pyramidal  zones  passing  through  the  pole  (0001)  it  takes  a  simpler  form,  viz.  : 

h  _  k  _  i  tan  PC 
p  ~  q  t  '  tan  QG' 
If  Q  =  (0111),  then  : 

tan  PC  _  k 

tanQO  ~  T' 

Determination  of  the  axis  c.—  The  value  of  c  may  be  determined  from  anyone  of  the 
equations  which  have  been  given.     The  following  are  simple  cases  : 

tan  (hh2h  2i)  (0001)  =  -. 

-  f  ^ 

Also  tan  (QhJti)  (0001)  .  sin  60°  =  ^?,  or  tan  (0111)  (0001)  .  sin  60°  =  c. 


MILLER  S    SYSTEM   OF   CRYSTALLOGRAPHY. 


415 


TV.   ORTHORHOMBIC    SYSTEM. 

The  Orthorhombic  System  is  characterized  by  three  unequal  rectangular  axes,  c,  £,  a.* 
The  indices  h,  &,  I  may  be  either  plus  or  minus,  in  the  general  form  [hkl],  but  they  are  not 
exchangeable,  since  they  refer  to  axes  of  different  lengths.  This  general  symbol  then  embraces 
the  following  planes : 

(hkl)  (hid)  (kfil)  (hid) 

(hkl)  (hkl)  (hkl)  (hkl) 

As  different  values  are  given  to  h,  k,  I,  this  general  form  becomes  more  or  less  specialized. 
The  possible  forms  are  as  follows  : 


;  7i>k. 

1.  [hkl}  ;  h>k. 
[hhl]  ;  h  =  k. 

2.  [Okl]  ;  &  =  0. 

3.  [hQl]  ;  h  =  Q. 
f[MO];  l  =  Q,  h>k. 

4.  -(  [hkO\  •  1  =  0,  h>k. 

I  [110J  ;  h  =  k  =  l,l  =  0. 

5.  [010J  ;  h  =  I  =  0. 
«.       [100];  k  =  l=0. 
7.      [001]  ;  h  =  k  =  0. 


nb  :  a  :  me 
b  :  na  :  me 

b  :_d  :  me 
ccb  :  a  :  me 
b  :  oo  a  :  me 
b  :  a  :  ooc 
b  :  na  :  oo  c 
b  :  no,  :  GO  c 
op  b  :  a  :  ooc 
b  :_co  a  :  GO  e 
oo  b  :  coa  :  c 


[m-n]. 

\rn-n}. 

\m\. 

[m-i]. 

[m-i]. 


[OJ. 


801 


110, 


These  symbols  belong  to  the  various  distinct  forms  of  this  system,  as  follows : 

Pinacm,d$.—(a)  Basal  plane.  Symbol  [001],  including  the  two  planes  (001)  and  (001).  (b) 
Macropinacoid.  Symbol  [010] ,  including  the  plane  (010),  and  (010)  opposite  to  it.  (c)  Brachy- 
pindcoid.  Symbol  [100],  including  the  planes  (100)  and  (100). 

Prisms.— (a)  Unit  prism  (/).  Symbol  110,  including  four  planes,  (110),  (110),  (110),  (110). 
(b)  Macrodiagonal  and  br achy  diagonal 
prisms,  having  respectively  the  symbols 
[MO]  and  [MO],  if  h  is  greater  than  k. 
Thus  the  symbol  i-2  corresponds  to  [120], 
and  i-2  to  [210]. 

Domes. — (a)  Macrodiagonal,  or  macro- 
domes,  having  the  symbol  [Okl  ]  ;  and  (b) 
brachydiagonal,  or  bruchydomes,  with  the 
symbol  [AO/].  In  each  case  the  symbol 
embraces  four  similar  planes. 

Octahedrons  or  Pyramids. — The  symbol 
[hhl]  belongs  to  the  eight  planes  of  the 
unit  pyramids,  all  lying  in  the  zone 
between  the  unit  prism  [110],  and  the 
base  [001].  If  h  =  I  the  form  is  then  [111] 
and  the  eight  _planes  are_:_  (111)^  (111), 
(111),  (111),  (111),  '(111),  (111),  (111). 

Of  the  general  pyramids  two  cases  are 
possible,  either  [khl]  or  [7ikl],  when  h>k, 
these  correspond  respectively  to  the  prisms 
[MO]  and  [MO].  They  are  the  macrodi- 
agonal  and  brachydiagonal  pyramids  of 
Naumann  ;  thus  2-2  (=  26  :  a  :  2J-)  is  [121], 
according  to  Miller,  and  2-i  (=  b  :  23,  :  26)  is  [211]. 


*  The  same  lettering  is  employed  here  as  in  the  early  part  of  this  work ;  it  differs  from  that 
of  Miller  in  that  with  him  a  is  the  macrodiagonal,  and  b  the  bracJiy 'diagonal  axis.  Following 
the  method  of  the  other  systems,  the  macropinacoid  should  have  the  symbol  (100),  and  the 
brachypinacoid  (010),  like  the  clinopinacoid  of  the  Monoclinic  System.  It  is  considered  best 
at  present,  however,  to  follow  Miller,  as  his  notation  is  nearly  universally  accepted.  This, 
however,  makes  it  necessary  to  write  the  formulas  after  Naumann,  b  :  na  :  me,  etc.,  thus 
showing  that  the  letter  h  refers  to  the  axis  b,  contrary  to  the  usage  in  the  other  systems.  It 
is  to  be  noticed  also  that  the  front  plane,  as  the  crystals  are  usually  drawn,  is  (010).  This  is, 
to  be  sure,  always  the  case  with  Miller,  but  other  authorities  make  the  same  plane  in  the 
monoclinic  and  triclinic  systems  (100),  so  that  entire  uniformity  is  in  no  case  possible. 


416  APPENDIX. 

For  the  figures  of  the  above-mentioned  forms  see  pp.  42-44.  Their  relations  will  be  under- 
stood from  an  examination  of  f.  801,  showing  the  projection  of  the  crystal  in  f.  758,  p.  402. 
It  will  be  seen  that  all  the  macrodiagonal  planes  lie  between  the  zonal  circles  (diameters) 
(110)  (001),  and  (010)  (001),  and  the  brachydiagonal  planes  between  (110)  (001)  and  (100)  (001). 

Mathematical  Relations  of  the  Orthorhombic  System. 

(1)  For  the  distance  between  the  pole  of  any  plane  P(hkl)  and  the  pinacoid  planes  we  have 
in  general  : 


cos*  PA  =  cos  W  (100)  = 
cos'  PB  =  cos  (kkt)  (010)  = 
cos2  PC  =  cos  (hkl)  (001)  = 


:2  +  k'2b'W  +  Z*asd8 

Furthermore  :  cot  PX  =  -=-7-  cos  PXY   =  -=j-  cos  PXZ. 

kb  to 

(2)  For  the  distance  (PQ)  between  the  poles  of  any  two  planes  (7tkl)  and  (pgr) : 
cos  PO  —     hpa^c*  +  kqbW  +  tra*b* 


(3)  For  planes  lying  in  a  zone,  the  general  relation  (p.  404)  is  to  be  employed.     For  the 
special  cases,  practically  of  most  importance,  the  simplified  equations  which  follow  are  used. 

(4)  To  determine  the  lengths  of  the  axes,  the  general  equation  may  be  employed : 

-T-  cos  PA  —  ~  cos  PB  =  4-  cos  PC. 
h  k  I 

Here  PA,  PB,  PC  are  the  distances  from  the  pole  of  any  plane  (hkl)  to  the  pinacoid  planes 
(100),  (010),  (001)  respectively.  The  brachydiagonal  axis,  a,  is  made  the  unit. 

If  the  angle  between  any  dome  or  prism  and  the  adjoining  pinacoid  plane  is  given,  the  rela- 
tions follow  immediately : 

tan  PA  =  tan  (hkO)  (100)  =  ^ 
ah 

tan  PB  =  tan  (Qkl)  (010)  =  ^ 
tan  PC  =  tan  (7iW)  (001)  = 


V.  MONOCLINIC  SYSTEM. 

In  the  Monoclinic  System  there  are  three  unequal  axes,  and  one  of  these  makes  an  oblique 
angle  with  a  second.     The  axes  are  lettered  as  shown  in  f.  802, 
r>^2  c  is  vertical,  b  the  orthodiagonal  axis,  and  a  the  clinodiagonal 

axis  oblique  to  c,  but  at  right  angles  to  b.  The  symbol  [hkl} 
embraces  only  four  similar  planes  in  the  most  general  case,  for 
in  consequence  of  the  obliquity  of  one  of  the  axes,  the  quadrants 
above  in  front  correspond  alone  to  those  below  and  behind,  and 
those  above  behind  correspond  to  those  below  in  front.  This  is 
seen  clearly  in  the  projection  of  f.  803.  For  ±h,  ±k.  ±1  the 
symbol  [hkl]  includes  two  distinct  forms,  viz. : 

(1)        (hkl}  (hkl}  (hkl)  (hH) 

and      (2)       (hkl)  (hkl)  (hkl)  (hhl) 

The  various  forms  are  as  follows : 


MILLER'S  SYSTEM  OF  CRYSTALLOGRAPHY. 


417 


Pinncoids. — Base   [001].     Orthopinacoid  [100].     Clinopinacoid  [010].      Each  symbol,   of 
course,  comprehending  two  planes  only. 

804: 


.120 


Crocoite. 


_  Prisms. — (a)  Unit  prism  [110],  =  d  :  b  :  ooc  (J)  of  Naumann.  This  symbol  embraces  four 
similar  prismatic  planes,  (b)  Orthodiagonal  prisms  [MO],  where  h  >  k,  the  poles  of  these 
prisms  fall  on  the  prismatic  zonal  circle  between  100  and  110  (see  f.  803).  They  correspond 
to  the  prisms  i-n  (=  d  :  rib  :  ooc)  of  Naumann.  (c)  Clinodiagonal  prisms.  Symbol  [MO], 
li  >  k,  lying-  between  (110)  and  (010).  They  correspond  to  i-n  (=nd  :  b  :  ooc)  of  Naumann. 

Domes. — (a)  Hemi-orthodomes,  including- two  cases,  (101)  and  (lOl),  the  minus  domes  of 
Naumann  (opposite  the  obtuse  angle)  ;  and  also  (101)  and  (101)),  the  plus  domes  of  Naumann 
(opposite  the  acute  angle  #).  (b)  Clinodomes.  Symbol  [QM] ,  embracing  four  similar  planes 
(OAtf)  (OK),  (O&O,  (O&Z).  The  clinodome  [Oil],  equivalent  to  1-i  (=ccd  :  b  :  me),  is  one  case 
in  this  form. 

Pyramids.  —  The  pyramids  are  all  hemi-pyramids.  (a]  The  symbol  \Jihl}  includes  the  unit 
pyramids  in  a  zone  between  [110]  and  [001].  (b)  The  symbol  [hkl\  includes  two  sets  of  hemi- 
pyramids,  whose  indices  have  been  given  on  p.  416,  corresponding  respectively  to  — P  and 
-+-P  of  Naumann. 

If  h  is  greater  than  k  these  are  orthodiagonal  pyramids,  corresponding  to  ±(d  :  nb  :  ooc)  of 
Naumann.  The  symbol  \khl]  on  the  same  supposition  includes  two  sets  of  planes,  like  those 
of  p.  416,  and  differing  only  in  being  dinodiagonal ;  equivalent  to  (nd  :  b  :  oo  c)  of  Naumann. 

The  orthodiagonal  planes  lie  between  the  zone  (100),  (001)  and  (110),  (001),  while  theclino- 
diagonal  are  between  the  latter  zone  and  (010)  (001),  as  is  seen  on  f.  803,  which  gives  the 
projection  for  f.  804. 


Mathematical  Relations  far  the  Monodinic  System. 

(1)  The  distances  of  the  pole  of  any  plane  (hkl)  from  the  pinacoid  planes  are  given  by  the 
following  equations  : 


cos' PA  =  cos  (hkl)  (100)  = 
cos  PB  =  cos  (hkl}  (010)  = 
cos  PC  =  cos  (hkl}  (001)  = 

27 


7ibo  +  lab  cos 


2  j8  +  l*a*b*  +  %hla¥c  cos  ft  ' 
kac  sin  ft 


cos/3 


lab  +  hbc  cos  ft 


l'2a-b-  + 


cos  ft 


418 


APPENDIX. 


(2)  The  distance  between  any  two  planes  may  be  expressed  in  general  form,  but  in  all 
practically  arising  cases  the  end  can  be  attained  by  the  solution  of  one  or  more  spherical  tri- 
angles on  the  projection. 

(3)  For  the  relation  between  the  planes  in  a  zone  the  general  equation  before  given  holds 
good: 

cot_PSj-_cot_PR  _   (PQ)  .  (SR) 
cot  PQ  —  cot~PR  "~  (QR)  .  (PS)' 

(4)  For  all  zones  passing  through  the  clinopinacoid  (010),  the  value  of  PR  may  be  taken  as 
90°,  and  the  above  equation  consequently  simplified  : 

7i  _k_       tan  PB  _   l_ 
~p  ~  q        tan  QB  ~  r  ' 

This  equation  is  especially  valuable  for  determining  the  indices  of  planes  in  the  prismatic 
and  clinodome  series. 

(5)  To  determine  the  axial  relations  the  general  equation  admits  of  being  transformed  so  as 
to  read  : 

h          sin  PYA  _  p          sin  QYA  _  a 
T  '       sin  PYC  ~~  r  '        sin  QYC  ~~  ~c  ' 


k          sin  PYA  _   q_          s^  _ 

T  '       ~^oT  PY  ~  ~f  '         cotQY  ~    ~c' 

The  angles  PYA,  PYC  are  angles  which  may  be  calculated  directly  by  spherical  triangles 
from  the  measured  angles.  Similarly  for  QYA,  QYC.  PY  and  QY  are  the  angles  between 
the  given  plane  P  or  Q  with  the  clinopinacoid. 


VI.  TRICLINIC  SYSTEM. 

In  the  Triclinic  System,  since  the  axes  are  unequal  and  all  mutually  oblique,  there  can  be 
no  plane  of  symmetry,  and  there  can  in  no  case  be  more  than  two  planes  included  in  a  single 
form._  The  three  axes  are  distinguished  as  a  vertical,  c,  a  longer  lateral,  or  macrodiagonal 
axis,  b,  and  a  shorter  lateral,  or  brachydiagonal  axis,  a.  The  position  assumed  for  the  axes 
is  shown  in  f.  259,  p.  80. 

The  general  symbol  \hkl\ ,  which  includes  eight  similar  planes  in  the  orthorhombic  system, 
is  here  resolved  into  four  independent  forms,  embracing  two  opposite  planes  only.  They 
are  thus : 

t9\    W  (^    &&)  ,,.    (hkl) 

(2)    (hkl)  <3)    (hkl)  (4)    (hkl} 

These  correspond  respectively  to  mP'n  (1),  m'Pn  (2),  mP,n  (3),  m,Pn  (4)  of  Naumann,  or 
—m-ri,  —m-n,  m-ri ,  m-ri ,  as  the  abbreviated  symbols  are  written  in  the  earlier  part  of  this 
work. 

Contrary  to  the  usage  in  the  orthorhombic  system,  it  is  customary  to  make  [100]  the 
macropinacoid  (i-l  =  a  :  oo  b  :  ooc),  and  [010]  the  brachypinacoid  (i-l  =  <x>d  :  b  :  occ).  Planes 
having  the  symbol  [hQt]  are  then  macrodomes ;  and  those  of  the  symbol  [O/W]  are  brachy- 
domes.  Similarly  then  pyramids  (h  >  k)  of  the  form  [hkl]  are  macrodiagonal  planes,  and 
those  of  the  form  (hkl)  are  brachydiagonal  planes.  The  unit  prism  consists  of  two  independent 
forms  (110),  (110)  (I'=ooP,'),  and  (110),  (110)  (I  =00  ',P). 

Mathematical  Relations  of  the  Triclinic  System. 

In  consequence  of  the  obliquity  of  the  axes  in  the  Triclinic  System  the  mathematical  rela- 
tions are  less  simple,  aud  the  general  equations  deduced  as  before  become  so  complicated  as 
to  be  seldom  of  much  practical  value.  Most  problems  which  arise  may  be  solved  by  the  zonal 
relations,  or  by  the  solution  of  the  spherical  triangles  in  the  projection.  Some  of  the  most 
important  relations  (given  by  Schrauf )  are  as  follows : 


MILLER'S  SYSTEM  OF  CRYSTALLOGRAPHY. 


419 


If  the  angle  between  the  axes  X  and  Z  =  rj,  between  X  and  Y  =  £  and  between  Y  and  Z 
=  £  (see  f.  759)  ;  if  also  a,  £,  y  are  the  corresponding  angles  between  the  pinacoid  planes — 
then  : 


cos  |  = 

and 
where 

Also 


cos  )8  cos  7  —  cos  a 
sin  £  sin  y 


COS  17  = 


cos  7  cos  a  —  cos 
sin  7  sin  a 


COS  )8  COS  a  —  COS  7 


cos         = 


cos'2  PZ  = 


j  =  [1  +  2  cos  a  cos  £  cos  7  —  (cos2  a  +  cos2  £  +  cos2  7)]. 


!  =  A26V  sin2  a  +  &2aV  sin2  j8  +  JV68  sin2  7  +  2afo  (M>  cos  0  sin  a  sin  7 
+  Tike  cos  7  sin  a  sin  #  +  kla  cos  a  sin  0  sin  7). 


cos2  AX  = 


__ 

sin'2  a 


cos  BY  =  — r-^-r-  ; 
sin2  £ 


cos  CZ  = 


sur  7 


When  PX,  PY,  PZ  have  been  found  by  calculation,  then  the  following  equation  gives  the 
relation  of  the  axes  : 

^r  cos  PX  =  —  cos  PY  =  —  cos  PZ. 

fl  Ki  I 

As  seen  in  f  .  805. 

cos  PX  =  sin  PEG  sin  PB  =  sin  PCB  sin  PC  ; 
cos  PY  =  sin  PGA  sin  PC  =  sin  PAG  sin  PA  ; 
cos  PZ  =  sin  PAB  sin  PA  =  sin  PBA  sin  PB  ; 
and  also  from  these  it  follows  that  — 

—  sin  PAG  =  -4-  sin  PAB  ; 
k  I 

ysinPBA=-|sinPBC; 


--  sin  PCB  =     -  sin  PGA. 
h  h 


-  180° 


CAB  ; 


=  180°  -  ABC  ; 


=  180°  -  ACB. 


RELATIONS  OP  THE  Six  CRYSTALLINE  SYSTEMS  IN  RESPECT  TO  SYMMETRY. 

From  a  careful  study  of  the  spherical  projections  for  the  successive  systems  a  very  clear 
idea  may  be  obtained  of  the  degree  of  symmetry  which  characterizes  each.  It  is  well  under- 
stood that  in  the  Isometric  System  there  are  nine  planes  of  symmetry ;  in  the  Tetragonal, 
jive ;  in  the  Hexagonal,  seven  ;  in  the  Orthorhombic,  three;  and  in  the  Monoclinic  only  one. 
These  relations  are  shown  on  the  projections  by  the  symmetrical  distribution  of  the  poles  about 
the  respective  great  circles.  These  zone-circles  of  symmetry  are  as  follows  : 

Isometric,  System  (f .  766) :  1st,  the  three  diametral  zones  : 


1.     (100),  (010),  (100). 
Also  the  diagonal  zones : 
4.     (110),  (001),  (110). 


5.     (110),  (001),  (110). 
Tetragonal  System  (f .  790)  : 

1.     (100),  (010),  (100). 
Also: 

4.     (110),  (001),  (110). 


2.     (100),  (001),  (100). 


6.  (100),  (Oil),  (TOO). 

7.  (100),  (Oil),  (100). 


2.     (100),  (001),  (100). 


3.     (010),  (001),  (010). 


8.  (010),  (101),  (010). 

9.  (010),  (101),  (010). 


3.    (010),  (001),  (010). 


5.     (110),  (001),  (110). 


420 


APPENDIX. 


Hexagonal  System  (f.  793) : 

1.    (1010),  (0001),  (1010). 
4.    (1120),  (0001),  (1120). 

OrthorkomMc  System  (f.  801) : 

1.     (100),  (010),  (100). 
Monodinic  System  (f.  804) : 


2.  (0110),  (0001),  (0110).  3.  (1100),  (0001),  (1100). 
5.  (1210),  (0001),  (1210).  6.  (2110),  (0001),  (2110). 
7.  (1010),  (0110),  (1100). 


2.     (100),  (001),  (100). 

1.     (100),  (001),  (100). 
In  the  Triclinic  System  there  is  no  plane  of  symmetry. 


3.     (010),  (001),  (010). 


THE  EHOMBOHEDRAL  DIVISION  OP  MILLER. 

The  following  projection  (f.  806)  is  added  in  order  to  show  the  relation  of  the  forms  in  the 

Hexagonal  and  Rhombohedral  Systems  as 
referred  to  the  three  equal  oblique  axes  of 
Miller.  The  forms  are  as  follows  : 

The  planes  having-  the  indices  (100), 
(010),  (001)  are  those  of  the  (plus)  funda- 
mental rhombohedron,  while  the  plane 
(111)  is  the  base.  The  planes  (221),  (121), 
(122)  are  those  of  the  minus  fundamental 
rhombohedron ;  with  the  planes  (100), 
(010),  (001)  they  form  the  unit  hexagonal 
pyramid. 

The  hexagonal  unit  prism  (/_=  [0110]) 
has  the  symbols  :  (21 1),  (121),  (112),  (211), 
(121),  (112).  The  second,  or  diagonal  hexa- 
gonal prism  (*-2_—  [1120])  has  the  symbols  : 
(101),  (110),  (Oil),  (101),  (110),  (Oil). 

The  dihexagonal  pyramid  embraces, 
like  the  simple  hexagonal  pyramid,  two 
forms,  \Jikl]  and  [efg] ;  the  symbol  [hM] 
hence  belongs  to  the  plus  scalenohedron, 
and  [efg]  to  the  minus.  In  this  as  in  other 
cases  it  is  true  that :  e  —  —  h  +  2k  +  2£, 
/  =  2h  -  k  +  21,  g  =  2h  +  2k  -  I. 

The  dihexagonal  prism  includes  the  six 
planes  of  the  form  [MO] ,  and  the  remain- 
ing six  of  the  form  [0/0]. 

Most  of  the  problems  arising  under  this  system  can  be  solved  by  the  zone  equations,  or 
by  the  working  out  of  the  spherical  triangles  on  the  sphere  of  projection. 


APPENDIX    B. 


ON  THE  DRAWING  OF  FIGURES  OF  CRYSTALS. 


IN  the  projection  of  crystals,  the  eye  is  supposed  to  be  at  an  infinite  distance,  so  that  the 
rays  of  light  fall  from  it  on  the  crystal  in  parallel  lines.  The  plane  on  which  the  crystal  is 
projected  is  termed  the  plane  of  projection.  This  plane  may  be  at  right  angles  to  the  ver- 
tical axis,  may  pass  through  the  vertical  axis,  or  may  intersect  it  at  an  oblique  angle.  These 
different  positions  give  rise,  respectively,  to  the  HORIZONTAL,  VERTICAL,  and  OBLIQUE  pro- 
jections. The  rays  of  light  may  fall  perpendicularly  on  the  plane  of  projection,  or  may  be 
obliquely  inclined  to  it ;  in  the  former  case  the  projection  is  termed  ORTHOGRAPHIC,  in  the 
second  CLINOGRAPHIC.  In  the  horizontal  position  of  the  plane  of  projection,  the  projection 
is  always  orthographic.  In  the  other  positions,  it  may  be  either  orthographic  or  clinographic. 
It  is  generally  preferable  to  employ  the  vertical  position  and  clinographic  projection,  and  this 
method  is  elucidated  in  the  following  pages. 


807 


PROJECTION  OF  THE  AXES. 

The  projection  of  the  axes  of  a  crystal  is  the  first  step  preliminary  to  the  projection  of  the 
form  of  the  crystal  itself.  The  projection  of  the  axes  in  the  isometric  system,  which  are 
equal  and  intersect  at  right  angles,  is  here  first  given.  The  projection  of  the  axes  in  the  other 
systems,  with  the  exception  of  the  hexagonal,  may  be  obtained  by  varying  the  lengths  of  the 
projected  isometric  axes,  and  also,  when  oblique,  their  inclinations,  as  shown  beyond. 

Isometric  System. — When  the  eye  is  directly  in  front  of  a  face  of  a  cube,  neither  the  sides 
nor  top  of  the  crystal  are  visible,  nor  the  planes  that  may  be 
situated  on  the  intermediate  edges.  On  turning  the  crystal 
a  few  degrees  from  right  to  left,  a  side  lateral  plane  is  brought 
in  view,  and  by  elevating-  the  eye  slightly,  the  terminal  plane 
becomes  apparent.  In  the  following  demonstration,  the 
angle  of  revolution  is  designated  8,  and  the  angle  of  the  ele- 
vation of  the  eye,  c.  Fig.  807  represents  the  normal  position 
of  the  horizontal  axes,  supposing  the  eye  to  be  in  the  direc- 
tion of  the  axis  BB  ;  BB  is  seen  as  a  mere  point,  while  CO 
appears  of  its  actual  length.  On  revolving  the  whole  through 
a  number  of  degrees  equal  to  BMB'  (8)  the  axes  have  the 
position  exhibited  in  the  dotted  lines.  The  projection  of  the 
semiaxis  MB  is  now  lengthened  to  MN,  and  that  of  the  semi- 
axis  MC  is  shortened  to  MH. 

If  the  eye  be  elevated  (at  any  angle,  e),  the  lines  B'N,  BM, 
and  C'H  will  be  projected  respectively  below  N,  M,  and  H. 

and  the  lengths  of  these  projections  (which  we  may  designate  J'N,  JM,  and  c'H)  will  be  di- 
rectly proportional  to  the  lengths  of  the  lines  B  N,  BM,  and  C'H. 

It  is  usual  to  adopt  such  a  revolution  and  such  an  elevation  of  the  eye  as  may  be  expressed 
by  a  simple  ratio  between  the  projected  axes.  The  ratio  between  the  two  axes,  MN  :  MH, 
as  projected  after  the  revolution,  is  designated  by  1  :  r ;  and  the  ratio  of  b'N  to  MN  by  1  :  8. 
Suppose  r  to  equal  3  and  s  to  equal  2,  then  proceed  as  follows : 


422 


APPENDIX. 


809 


Draw  two  lines  AA',  H'H  (f.  808),  intersecting  one  another  at  right  angles.     Make  MH  = 

MH'  =  ft.  Divide  HH'  into  3  (r)  parts,  and  through  the 
points,  N,  N',  thus  determined,  draw  perpendiculars  to 
HH'.  On  the  left  hand  vertical,  set  off,  below  H',  a 

part  H'R,  equal  to—  ft  =  —  H  M;  and  from  R  draw  RM, 

and  extend  the  same  to  the  vertical  N'.  B'B  is  the  pro- 
jection of  the  front  horizontal  axis. 

Draw  BS  parallel  with  MH  and  connect  SM.  From 
the  point  T  in  which  SM  intersects  BN,  draw  TC  par- 
allel with  MH.  A  line  (CCr)  drawn  from  C  through  M, 
and  extended  to  the  left  vertical,  is  the  projection  of  the 
side  horizontal  axis. 

Lay  off  on  the  right  vertical,   a  part  HQ  equal    to 

-MH,  and  make  MA  =  MA'=  MQ  ;  AA'  is  the  vertical 
o 

axis.  If,  as  here,  r  =  3,  and  s  -  2,  then  5  =  18°  26', 
and  e  —  9°  28',  for  cot  8  =  r,  and  cot  e  =  rs. 
Tetragonal  and  Orthorhombic  Systems. — The  axes  AA',  CC',  BB,  constructed  in  the  manner 
described,  are  equal  and  at  right  angles  to  each  other.  The  projection  of  the  axes  of  a  tetra- 
gonal crystal  is  obtained  by  simply  laying  off,  with  a  scale  of  proportional  parts,  on  MA  and 
MA'  taken  as  units,  the  value  of  the  vertical  axis  (c)  for  the  given  species.  Thus  for  zircon, 
where  c  =  '64,  we  must  lay  off  '64  of  MA  above  M  and  the  same  length  below. 

For  an  orthorhombic  crystal,  where  the  three  axes  are  unequal,  the  length  of  c  must  as 
before  be  laid  off  above  and  below  from  M,  and  that  of  b  to  the  right  and  left  of  M,  on  CC', 
MC  being  taken  as  the  unit.  It  is  usual  to  make  the  front  axis  MB  =  d  =  1. 

Monoclinic  System. — The  axes  c  and  d  in  the  monoclinic  system  are  inclined  to  one  another 

at  an  obliqe  angle  =  /8.  To  project  this  inclination,  and 
thus  adapt  the  isometric  axes -to  a  monoclinic  form,  lay 
off  (f.  809)  on  the  axis  MA,  M«  =  MA  cos  0,  and  on  the 
axis  BB'  (before  or  behind  M,  according  as  the  inclination 
of  d  on  c,  in  front,  is  acute  or  obtuse)  Mft  =  MB  x  sin  £. 
From  the  points  ft  and  «,  draw  lines  parallel  respectively 
with  the  axes  AA'  and  BB',  and  from  their  intersection 
D',  draw  through  M,  D'D,  making  MD  =  MD  .  The  line 
DD'  is  the  clinodiagonal,  and  the  lines  AA,  C'C,  DD'  re- 
present the  axes  in  a  monoclinic  solid  in  which  a  =  ft  =  c 
=  1.  The  points  a  and  ft  and  the  position  of  the  axis 
DD'  will  vary  with  the  angle  /8.  The  relative  values  of 
the  axes  may  be  given  them  as  above  explained ;  that  is, 
if  d  =  1,  lay  off  in  the  direction  of  MA  and  MA'  a  line 
equal  to  c,  and  in  the  direction  of  MC  and  MC'  a  line 
equal  to  ft,  etc. 

Triclinic  /System. — The  vertical  sections  through  the 
horizontal  axes  in  the  triclinic  system  are  obliquely  in- 
clined ;  also  the  inclination  of  the  axis  a  to  each  axis  ft 
In  the  adaptation  of  the  isometric  axes  to  the  triclinic  forms,  it  is  there- 
fore necessary,  in  the  first  place,  to  give  the  requisite 
obliquity  to  the  mutual  inclination  of  the  vertical  sec- 
tions, and  afterwards  to  adapt  the  horizontal  axes.     The 
inclination  of  these  sections  we  may  designate  A,  and  as 
heretofore,  the  angle  between  a  and  ft,  7,  and  a  and  c,  0. 
BB'  is  the  analogue  of  the  brachy  diagonal,  and  CC  of  the 
macrodiagonal.     An  oblique  inclination  may  be  given  the 
Jj*  vertical  sections,  by  varying  the  position  of  either  of 

-  these  sections.  Permitting  the  brachy  diagonal  section 
ABA  B'  to  remain  unaltered,  we  may  vary  the  other  sec- 
tion as  follows : 

Lay  off  (f.  810)  on  MB,  Mft  =  MB  x  cos  A,  and  on  the 
axis  C  C  (to  the  right  or  left  of  M,  according  as  the 
acute  angle  A  is  to  the  right  or  left),  Me  =  MC  x  sin  A  ; 
completing  the  parallelogram  Mft'  DC,  and  drawing  the 
diagonal  MD,  extending  the  same  to  D'  so  as  to  make 
MD'—  MD,  we  obtain  the  line  DD' ;  the  vertical  section 


and  c,  is  oblique. 

810 
A 


ON   THE   DRAWING    OF   FIGURES    OF   CRYSTALS. 


4:23 


passing-  through  this  line  is  the  correct  macrodiagonal  section.  The  inclination  of  a  to  the 
new  macrodiagonal  DD'  is  still  a  right  angle  ;  as  also  the  inclination  of  a  to  #,  their  oblique 
inclinations  may  be  given  them  as  follows:  Lay  off  on  MA  (f.  809),  M#  =  MA  x  cos  £,  and 
on  the  axis  BB'  (brachydiagonal),  Mb  —  MB'  x  sin  £.  By  completing  the  parallelogram  M«, 
E'ft,  the  point  E'  is  determined.  Make  ME  =  ME';  EE'  is  the  projected  brachydiagonal. 
Again  lay  off  on  MA,  ~M.a'=  MAx  cos  o,  and  on  MD',  to  the  left.  Mrf  =  MD'  x  sin  a.  Draw 
lines  from  a'  and  d  parallel  to  MD  and  MA ;  F',  the  intersection  of  these  lines,  is  one  extremity 
of  the  macrodiagonal;  and  the  line  FF',  in  which  MF  =  MF',  is  the  macrodiagonal.  The 
vertical  axis  AA'  and  the  horizontal  axes  EE'  (brachydiagonal)  and  FF'  (macrodiagonal)  thus 
obtained,  are  the  axes  in  a  triclinic  form,  in  which  a  —  b  —  c  =  1.  Different  values  may  be 
given  these  axes,  according  to  the  method  heretofore  illustrated. 

Hexagonal  System. — In  this  system  there  are  three  equal  horizontal  axes,  at  right  angles  to 
the  vertical  axis.  The  normal  position  of  the  horizontal 
axes  is  represented  in  f.  811.  The  eye,  placed  in  the 
line  of  the  axis  YY,  observes  two  of  the  semiaxes,  MZ 
and  MU,  projected  in  the  same  straight  line,  while  the 
third,  MY,  appears  a  mere  point.  To  give  the  axes  a 
more  eligible  position  for  a  representation  of  the  various 
planes  on  the  solid,  we  revolve  them  from  right  to  left 
through  a  certain  number  of  decrees  8,  and  elevate  the 
eye  at  an  angle  e.  The  dotted  lines  in  the  figure  repre- 
sent the  axts  in  their  new  situation,  resulting  from  a 
revolution  through  ^  a  number  of  degrees  equal  to  8  — 
YMY'.  In  this  position  the  axis  MY  is  projected  upon 
MP,  MU'  upon  MN,  and  MZ'  on  MH.  Des'gnating  the 
intermediate  axis  I,  that  to  the  right  II,  that  to  the  left 
III,  if  the  revolution  is  such  as  to  give  the  projections 
of  I  and*ll  the  ratio  of  1  :  2,  the  relations  of  the  three 
projections  will  be  as  follows  :  I  :  II  :  III  =  1:2:3. 

Let  us  take  r  (=  PM  :  HM)  equal  to  3,  and  s  (=  b'P  : 
PM)  equal  to  2,  these  being  the  most  convenient  ratios  for 

representing  the  hexagonal  crystalline  forms.  The  following  will  be  the  mode  of  construc- 
tion : 

1.  Draw  the  lines  AA,  HII  (f.  812)  at  right  angles  with,  and  bisecting,  each  other.     Let 
HM  =  6,  or  HH  —  2b.     Divide  HH  into  six  parts  by  vertical  lines.     These  lines,  including 
the  left-  and  right-hand  verticals,  may  be  numbered  from  one  to  six,  as  in  the  figure.     In  the 
first  vertical,  below  H,  lay  off  HS  =  %b,  and  from   S  draw  a  line  through  M  to  the  fourth 
vertical.     YY  is  the  projection  of  the  axis  I. 

2.  From  Y  draw  a  line  to  the  sixth  vertical  and  parallel  with  HH.     From  T,  the  extremity 
of  this  line,  draw  a  line  to  N  in  the  second  vertical. 

Then  from  the  point  U,  in  which  TN  intersects  the 
fifth  vertical,  draw  a  line  through  M  to  the  second 
vertical ;  UU'  is  the  projection  of  the  axis  II. 

3.  From  R,  where  TN  intersects  the  third  verti- 
cal, draw  RZ  to  the  first  vertical  parallel  with  HH. 
Then  from  Z   draw  a  line  through  M  to  the  sixth 
vertical :  this  line  ZZ'  is  the  projection  of  the  axis 
III. 

4.  For  the  vertical  axis,  lay  off  from  IS"  on  the  sec- 
ond vertical  (f.  812)  a  line  of  any  length,  and  con- 
struct upon  this  line  an  equilateral  triangle  ;  one  side 
(NQ)  of  this  triangle  will  intersect  the  first  vertical 
at  a  distance,  HV,  from  H,  corresponding  to  Z  H  in 
f .  811;  for  in  the  triangle  NHV,  the  angle  HNV  is 
an  angle  of  30°,  and  HN  =  iMH.     MV  is  therefore 
the  radius  of  the  circle  (f.  811).     Make  therefore 
MA  =  MA'=  MV  ;  AA'  is  the  vertical  axis,  and  YY', 
UU',  ZZ'  are  the  projected  horizontal  axes. 

The  vertical  axis  has  been  constructed  equal  to  the  horizontal  axes.  Its  actual  length  in 
different  hexagonal  or  rhombohedral  forms  may  be  laid  off  according  to  the  method  sufficiently 
explained. 

The  projection  of  the  isometric  and  hexagonal  axes,  having  been  once  accurately  made,  and 
that  on  a  conveniently  large  scale,  may  be  kept  on  a  piece  of  cardboard,  and  will  then  answer 
all  subsequent  requirements.  Whenever  needed  for  use,  these  axes  may  be  transferred  to  a 
sheet  of  paper,  and  then  adapted  in  length,  or  inclination,  or  both,  to  the  case  in  hand. 


424 


APPENDIX. 


EL. — X   c 


PROJECTION  OF  THE  FORMS  OF  CRYSTALS. 

1.  Simple  forms. — When  the  axial  cross  has  been  constructed  for  the  given  species,  the  unit 

octahedron  is  obtained  at  once  by  joining  the 
extremities  of  the  axes,  AA',  BB',  CO',  as  in 
f.  813.  Here  as  in  all  cases  the  lines  which 
fall  in  front  are  drawn  strongly,  while  those 
behind  are  simply  dotted. 

For  the  diametral  prisms  draw  through  B, 
B',  C,  C',  of  the  projected  axes  of  any  species, 
lines  parallel  to  the  axes  BB  ,  CC',  until  they 
meet ;  they  make  the  parallelogram,  abed, 
which  is  a  transverse  section  of  the  prism,  par- 
allel  *°  the  base>  Through  «,  b,  c,  d  draw 
lines  parallel  and  equal  to  the  vertical  axis, 
making  the  parts  above  and  below  these  points 
equal  to  the  vertical  semiaxis.  Then,  connect 
the  extremities  of  these  lines  by  lines  parallel 
to  ab,  be,  cd,  da,  and  the  figure  will  be  that  of 
the  diametral  prism,  corresponding  to  the  axes 
projected. 

In  the  case  of  the  isometric  system  this  dia- 
metral prism  is  the  cube,  whose  faces  are  represented  by  the  letter  H;  in  the  tetragonal 
system  it  is  the  prism  0,  i-i ;  in  the  orthorhombic,  the  prism  0,  i-l,  i-i ;  in  the  monoclinic,  the 
prism  0,  i-i.  i-l ;  in  the  triclinic,  0,  i-1,  i-i. 

The  unit  vertical  prism  in  the  tetragonal,  orthorhombic,  and  clinometnc  systems  may  be 
projected  by  drawing  lines  parallel  to  the  vertical  axis  AA'  through  B,  C,  B',  C',  making  the 
parts  above  and  below  these  points  equal  to  the  vertical  semiaxis ;  and  then  connecting  the 
extremities  of  these  lines  by  lines  parallel  to  BC,  CB',  B'C  ,  C  B.  The  plane  BCB'C  is  a 
transverse  section  of  such  a  prism  parallel  to  its  base.  It  is  the  prism  (9,  /,  in  each  of  the 
systems  excepting  the  triclinic,  and  in  that  0,  /,  /' ;  a  square  prism  in  the  tetragonal  system  ; 
a  right  rhombic  in  the  orthorhombic ;  an  oblique  rhombic  in  the  monoclinic ;  an  oblique  rhom- 
boidal  in  the  triclinic. 

Other  simple  forms  under  the  different  systems  are  constructed  in  essentially  the  same  way. 
It  is  only  necessary  to  lay  down  upon  the  axes  each  plane  of  the  form,  in  lightly  drawn  lines, 


note  the  points  where  it  intersects  the  adjoining  planes,  and  draw  these  in  more  strongly. 
When  the  process  is  complete  the  construction  lines  may  be  erased.  The  process  will  be 
illustrated  by  f .  814  and  f .  815.  In  the  former  case  it  is  required  to  draw  the  trigonal  trisoc- 
tahedron,  whose  symbol  is  2. 


ON   THE   DRAWING    OF    FIGURES    OF    CRYSTALS.  425 

In  f .  814  the  three  planes  of  the  first  octant  are  represented,  they  are  2:1:1,1:2:1, 
and  1:1:2.  It  will  be  seen  here,  what  is  always  true,  that  the  two  points  of  intersection 
required  to  determine  the  line  of  intersection,  lie  in  the  axial  planes.  These  lines  of  intersec- 
tion are  represented  by  the  dotted  lines  in  f.  814.  If  the  same  process  be  performed  for  the 
other  octants,  the  complete  form,  as  in  f.  816,  will  be  obtained. 

Similarly  in  f.  815,  the  octagonal  pyramid  1-2  is  constructed;  the  figure  shows  the  planes 
of  one  octant  only,  c  :  2a  :  a,  and  c  :  a  :  2a,  and  the  dotted  line  gives  their  line  of  intersec- 
tion. Carry  out  the  same  plane  of  constr action  in  the  other  octants,  and  the  form,  of  f.  817 
will  result. 

The  construction  of  the  various  crystalline  forms,  by  this  method,  especially  those  of  the 
isometric  sjrstem,  will  be  found  an  interesting  and  instructive  process,  and  will  lead  to  a  clear 
understanding  of  the  forms  themselves  and  their  relations  to  each  other.  Another  and  quicker, 
though  more  mechanical  method  of  constructing  the  isometric  forms  may  also  be  given. 

Projection  of  Simple  Isometric  Forms. — This  method  depends  upon  the  principle  that  in  the 
different  isometric  forms  the  vertices  of  the  solid  angles  are  occupied  by  one  or  more  of  the 
interaxes  (p.  16).  If,  therefore,  these  points  (the  extremities  of  the  interaxes),  can  be  deter- 
mined in  the  several  crystalline  forms,  it  is  only  necessary  to  connect  them  in  order  to  obtain 
the  projection  of  the  solid  itself. 

As  a  preparation  for  the  construction  of  figures  of  isometric  crystals,  it  is  desirable  to  have 
at  hand  the  figure  of  a  cube  projected  on  a  large  scale,  with  its  axes,  and  its  trigonal  (octahe- 
dral), and  rhombic  (dodecahedral)  interaxes. 

The  values  of  the  interaxes  t  and  r,  for  a  given  form,  are  obtained  by  adding  to  their  nor 
mal  length  the  values  of  t'  and  r'  respectively  given  by  the  following  equations ;  those  of  the 
octahedron  being  taken  as  a  unit : 

,       2mn  —  (m  +  n)          ,       n  —  1 

mn  +  (m  +  n)   '         ~  n  +  1  ' 
The  proportion  to  be  added  to  the  interaxes  for  some  of  the  common  forms  is  as  follows: 

t  r  t  r 

2  i  0  i-2  1  i 

*  i  0  £-3  f  i 

S-|  I'"'*  2-2  *  * 

4-2  f  i  3-3  £  i 

To  construct  the  form  4-2,  the  octahedron  is  first  to  be  projected,  and  its  axes  and  inter- 
axes drawn.  Then  add  to  each  half  of  each  trigonal  interaxis,  five-sevenths  of  its  length ; 
and  to  each  half  of  each  rhombic  interaxis,  one-third  of  its  length,  The  extremities  of  the 
lines  thus  extended  are  situated  in  the  vertices  of  the  solid  angles  of  the  hexoctahedron  4-2, 
and  by  connecting  them,  the  projection  of  this  form  is  completed. 

In  the  inclined  hemihedral  isometric  forms  (p.  20),  the  rhombic  interaxes  do  not  terminate 
in  the  vertices  of  the  solid  angles,  and  may  therefore  be  thrown  out  of  view  in  the  projection 
of  these  solids.  The  two  halves  of  each  trigonal  interaxis  terminate  in  the  vertices  of  dis- 
similar angles,  and  are  of  unequal  lengths.  One  is  identical  with  the  corresponding  interaxis 
in  the  holohedral  forms,  and  is  called  the  holohedral  portion  of  the  interaxis  ;  the  other  is  the 
hemihedral  portion.  The  length  of  the  latter  may  be  determined  by  adding  to  the  half  of 
the  octahedral  interaxis  that  portion  of  the  same  indicated  in  the  formula  : 

2mn  —  (m  —  n) 
mn  +  (m  —  n)  ' 

If  the  different  halves  of  the  trigonal  interaxes  be  assumed  at  one  time,  as  the  holohedral, 
and  again  as  the  hemihedral  portion,  the  reverse  forms and  —  —  may  be  projected. 

The  following  table  contains  the  values  cf  the  above  fraction  for  several  of  the  inclined 
hemihedral  forms,  and  also  the  corresponding  values  for  the  holohedral  portion  of  the  inter- 
axis : 

Hoi.  interax.    Hem.  interax.  Hoi.  interax.    Hem.  interax, 

(-^-  (f.  76,  p.  20)        02®-  (f.  85)  i  1 


426 


APPENDIX. 


The  parallel  JiemiJiedrom  (for  example,  the  pentagonal  dodecahedron,  or  hemi-tetrahexahe- 
dron)  contain  a  solid  angle,  situated  in  a  line  between  the  extremities  of  each  pair  of  semiaxes, 
which  is  called  an  unsymmetrical  solid  angle.  The  vertices  of  these  angles  are  at  unequal 
distances  from  the  two  adjacent  axes,  and  therefore  are  not  in  the  line  of  the  rhombic  inter- 
axes.  The  co-ordinates  of  this  solid  angle  for  any  form,  as  -  ,  may  be  found  by  the  for- 
mulas —  -—  and  -  — .  By  means  of  these  formulas,  the  situation  of  two  points,  a 

and  b  (f.  818),  in  each  of  the  axes  may  be  determined  :  and  if  lines  are  drawn  through  a  and 
b  in  each  semiaxis  parallel  to  the  other  axes,  the  intersections  c  c',  of  these  lines  will  be  the 


vertices  of  the  unsymmetrical  solid  angles,  those  marked  c  of  the  form 

[m-?i] 
c  of  the  form  —  ^—^ 

V 


[m-n] 


and  those  marked 


The  trigonal  interaxes  are  of  the  same  length  as  in  the  holohedral  forms.  The  values  of 
these  interaxes,  and  of  the  coordinates  of  the  unsymmetrical  solid  angle  for  different  parallel 
hemihedrons,  are  contained  in  the  following  table  : 


Trigonal 
interaxis. 


[3-f] 


(f.  100,  p.  23) 


Coord,  of  the 
unsym.  S.  A. 


Trigonal 
interaxis. 


(sim.  f.  92) 


Coord,  of  the 
unsym.  S.  A. 


[4-2J 
2 


(f.  92) 


Projection  of  a  Rhombohedron. — To  construct  a  rhombohedron,  lay  off  verticals  through  the 
extremities  of  the  horizontal  axes,  and  make  the  parts  both  above  and  below  these  extremities 
equal  to  the  third  of  the  vertical  semiaxis  (f.  819).  The  points  E,  E,  E',  B',  etc.,  are  thus 
determined  ;  and  if  the  extremities  of  the  vertical  axis  be  connected  with  the  points  E  or  E', 
rhombohedrons  in  different  positions,  wR,  or  — mR,  will  be  constructed. 

Scalenohedron. — The  scalenohedron  mn  admits  of  a  similar  construction  with  the  rhombohe- 
dron mR.  The  only  variation  required,  is  to  multiply  the  vertical  axis  by  the  number  of 
units  in  n,  after  the  points  E  and  E'  in  the  rhombohedron  mR  have  been  determined  ;  then 
connect  the  points  E,  or  the  points  E',  with  one  another  and  with  the  extremities  of  the  ver- 
tical axis. 

2.  Complex  Forms. — When  it  is  required  to  figure  not  only  the  planes  of  one  form,  that 
is,  those  embraced  in  one  symbol,  but  also  those  of  a  mimber  modifying  one  another,  a  some- 
what different  process  is  found  desirable.  It  is  possible  indeed  to  construct  a  complex  form 
in  the  way  mentioned  on  p.  424.  each  plane  being  laid  off  on  the  given  axes,  and  its  intersec- 
tion-edges with  adjoining  planes  determined  by  two  points,  always  in  the  axial  sections,  which 
it  has  in  common  with  each.  In  this  way,  however,  the  figure  will  soon  become  so  complex 
as  to  be  extremely  perplexing,  and  thus  lead  to  error  and  consequent  loss  of  time. 

This  difficulty  is  in  part  avoided  by  the  use  of  one  projection  of  the  axes  on  a  larger  scale, 
upon  which  the  directions  of  the  intersection-lines  are  determined,  while  a  second  smaller  one, 


ON   THE   DBA  WING    OF   FIGURES   OF    CRYSTALS. 


427 


placed  below  and  parallel  to  it  on  the  same  sheet  of  paper,  is  used  for  the  actual  drawing  of 
the  crystal.  In  most  cases,  however,  the  crystal  may  be  drawn  as  conveniently  without  the 
use  of  the  second  set  of  axes.  The  size  of  the  figure  may  be  either  that  which  is  to  be  finally 
required,  or,  more  advantageously,  it  maybe  drawn  two  or  three  times  larger  and  then  reduced 
by  photography.  This  method  is  especially  to  be  recommended  when  the  figures  are  finally 
to  be  engraved  on  wood,  since  from  the  enlarged  drawing  they  may  be  photographed  directly 
upon  the  wood  of  a»y  required  size,  and  thus  a  very  high  degree  of  accuracy  attained. 

Application  of  Quenstedfs  Projection.  —  The  process  of  determining  the  direction  of  the 
intersection-edges  is  much  simplified  if  the  principles  of  Quenstedt's  Projection  (p.  55)  are 
made  use  of.  In  other  words,  the  symbol  of  every  plane  is  so  transformed  that  for  it  tin 
length  of  the  vertical  axis  is  unity.  This  extremity  of  the  vertical  axis  is  then  one  point  of 
intersection  for  all  planes  whatsoever,  and  the  second  point  will  always  lie  in  the  horizontal 
plane,  that  of  the  lateral  axes.  The  change  in  the  symbol  requires  nothing  but  that  the 
symbol,  expressed  in  full,  should  be  divided  by  the  coefficient  of  the  vertical  axis.  The  direc- 
tion of  each  intersection-edge,  when  determined,  is  transferred  to  the  figure  in  process  of 
construction  by  means  of  a  small  triangle  sliding  against  a  ruler  some  8  inches  in  length.  It 
will  be  found  in  practice  that,  especially  when  this  method  is  employed,  it  is  not  necessary 
to  actually  draw  all  the  lines  representing  each  plane,  but  to  note  simply  the  required  points 
of  intersection.  This  method  and  its  advantages  (see  Klein,  Einleitung  in  die  Krystallberech- 
nung,  II.,  p.  387)  will  be  made  clear  by  an  example. 

It  is  required  to  project  a  crystal  of  andalusite  of  prismatic  habit,  showing  also  the  planes 
*-2,  H  1  4,  1,  2-2,  \-i,  and  0. 

It  is  evident  that  an  indefinite  number  of  figures  may  be  made,  including  the  planes  men- 
tioned, and  yet  of  very  different  appearance  according  to  the  relative  size  of  each.  It  is 
usually  desirable,  however,  to  represent  the  actual  appearance  of  the  crystal  in  nature,  only 
in  ideal  symmetry,  hence  it  is  very  important  in  all  cases  to  have  a  sketch  of  the  crystal  to 
be  represented,  showing  the  relative  development  of  the  different  planes.  If  this  sketch  is 
made  with  a  little  care,  so  as  to  show  also  the  parallelism  of  the  intersection-edges  in  the 
occurring  zones,  it  will  give  material  aid.  The  zones,  it  is  to  be  noted,  are  a  great  help  in 
drawing  figures  of  crystals,  and  they  should  be  carefully  studied,  since  the  common  direction 
of  the  intersection-edge  once  determined  for  any  two  planes  in  it,  will  answer  for  all  others. 


The  first  step  is  to  take  the  projection  of  the  isometric  axes  already  made  once  far  all  on 
a  conveniently  large  scale,  and  which,  as  before  suggested,  is  kept  on  a  card  of  large  size, 
and  ready  to  be  pierced  through  on  to  the  paper  employed.  These  axes,  now  of  equal  length, 
must  be  adapted  to  the  species  in  hand.  For  andalusite  the  axial  ratio  is  <'  :  b  :  <1  =  0'712  : 
1-014  :  1  ;  hence  the  vertical  axis  c  must  have  a  length  -71  of  what  it  now  has,  and  the  lateral 
axis  one  I'Ol  ;  these  required  lengths  are  determined  in  a  moment  with  a  scale  of  equal  parts. 

The  next  step  is  to  draw  the  predominating  form,  the  prism  1.  Obviously  its  intersection- 
edges  are  parallel  to  the  vertical  axis,  and  its  basal  edges,  intersecting  0,  are  parallel  to  ps, 
tq  in  the  projection  (f,  820).  The  planes  i-l,  and  i-  2  are  now  to  be  added,  whose  intersections 
with  each  other  and  with  1  are  parallel  to  /•.  The  position  of  one  edge,  /  i-'l,  having  been 
taken,  that  of  the  other  on  the  other  side  is  determined  by  the  point  where  a  line  parallel  to 


428 


APPENDIX. 


the  axis  f>  meets  the  basal  edge  of  the  pri.cm.     Similarly  the  position  of  the  same  prismatic 
edges  behind  are  given  by  the  intersection  of  lines  from  front  to  rear  parallel  to  the  axis  J. 

The  prisms  drawn,  it  remains  to  add  the  terminal  planes,  and  as  they  thus  modify  one  an- 
other's position,  they  are  drawn  together.  The  required  intersection-lines  are  easily  obtained. 
The  macrodome  l-l  is  the  plane  passing  through  the  point  c  and  intersecting  the  horizontal 
plane  in  the  line  paq  ;  this  line  is  obviously  the  direction  of  its  intersection-edge  with  i-l  and 
with  0.  The  prism  i-2  appears  (f.  820)  as  the  two  lines  mm',  nri  ;  tne  line  mm'  produced 
beyond  m  meets  paq  at  2,  this  will  be  one  common  point  for  the  two  planes  1-?  and  i-2  ;  the 
second  common  point  is,  as  always,  the  point  c,  hence  the  line  joining  these  two  points,  trans- 
ferred to  the  crystal  in  the  way  described,  gives  the  required  intersection-edge  for  i-2  and  1-*. 
Similarly  for  i-2  on  the  right,  the  two  points  of  intersection  are  c,  and  the  point  where  rin 
and  gap,  produced,  meet,  and  this  gives  the  second  intersection-edge.  The  planes  l-l  and  1 
(right)  meet  at  d  and  c  ;  hence  the  line  cd  gives  the  direction  of  their  intersection-edge,  which 
is  also  the  direction  of  that  of  l-l  and  1  (left),  and  of  1  and  2-5,  right  and  left  on  both  sides. 
Still  again,  the  plane  2-2  has  the  full  symbol  2  '•  :  b  :  2  ?,  or  c  :  %?>  :  d  ;  and  hence  intersects  the 
horizontal  plane  (f.  820)  in  the  lines  as  (right),  at  (left),  and  a'q,  a'p  (behind).  Hence  the 
intersection-edge  of  7,  2-2,  \-l  has  the  direction  of  the  line  joining  the  points  c  and  s  (right), 
and  similarly  to  the  left  and  behind.  The  intersection-  edge  of  2-2  front,  and  2-2  behind,  has 
the  direction  of  the  line  joining  the  points  c  and  x  (right)  and  c  and  y  (left). 

The  method  of  obtaining  the  intersection-edges  of  the  planes  will  be  clear  from  this  ex- 
ample.    Practical  facility  in  drawing  figures  by  this  or  any  other 
Q21  method  is  only  to  be  obtained  by  practice. 

It  will  be  found  that  at  almost  every  step  there  is  an  opportunity 
to  test  the  accuracy  of  the  work  —  thus  every  point  of  intersection 
on  the  basal  plane  behind  must  lie  on  a  line  drawn  from  the  cor- 
responding point  in  front  on  the  basal  plane,  in  the  direction  of  the 
axis  d;  so,  too,  the  point  of  intersection  of  2-2  and  2  (front),  2-2 
and  I  (behind),  on  one  side,  must  be  in  the  line  of  the  horizontal 
axis  (J)  with  that  on  the  other  side,  and  similarly  in  other  cases. 

If  it  were  required,  as  is  generally  necessary,  to  complete  the 
form  (f  .  821)  below,  it  is  unnecessary  to  obtain  any  new  intersec- 
tion lines,  since  every  line  above  has  its  corresponding  line  oppo- 
site and  parallel  to  it  below.  Moreover,  in  an  orthorhombic  crys- 
tal every  point  above  has  a  corresponding  point  below  on  a  line 
parallel  to  the  vertical  axis.  This,  as  above,  will  serve  as  a  control 
of  the  accuracy  of  the  work. 

There  is  another  method  of  drawing  complex  crystalline  forms 
which  has  many  advantages  and  is  sometimes  to  be  preferred  to 
any  other-;  it  can  be  explained  in  a  very  few  words.  After  the 

axes  have   been  obtained  the  diametral  prism  is  constructed  upon  them.     Upon  the  solid 
angles  of  this  each  plane  of  the  required  form  is  laid  off,  the  edges  being  taken  instead  of  the 


iz 


822 


823 


824 


M 


M 


axes.  Suppose  that  f.  822  represents  the  diametral  prism  of  an  orthorhombic  crystal.  Here 
obviously  the  edge  e  =  2:',  e  =  2b,  e  =  2 1.  The  plane  1  (c  :  b  :  d)  may  be  laid  off  on  it  by 
taking  from  the  angle  a  equal  portions  of  the  edges  e,  e,  e,  for  instance,  conveniently  one 


ON   TEE   DRAWING   OF   FIGURES    OF   CRYSTALS. 


429 


half  of  each,  hence  the  plane  appears  as  mno.  Again  the  plane  2  (2c  :  I  :  a)  is  laid  off  by  taking 
the  unit  lengths  of  the  edges  e  (&),  and  e  (a)  and  twice  the  unit  length  of  e  (<?),  the  plane  is 
then  mnl.  Again,  the  plane  4-2"  (4«  :  b  :  2.1)  takes  the  position  npb,  since  ap  =  2c,  ap  =  $b, 
and  an  =  a,  the  ratio  of  the  edges  (axes)  being  the  same  as  in  the  symbol.  So  also  the  plane 
2-2  (2c  :  2b  :  ft)  has  the  position  rmo,  since  ao  =  c,  am  =  b,  and  ar  =  -£a,  here,  too,  the 
ratio  of  the  axes  being  preserved.  By  plotting  the  successive  planes  of  the  crystal  in  this 
way,  each  solid  angle  corresponding  to  an  octant,  the  direction  of  the  intersection -edges 
for  the  given  form  are  at  once  obtained.  For  example,  the  intersection -edge  for  1,  and  the  basal 
plane,  as  also  for  1  and  2,  it  is  the  line  inn  ;  for  1  and  4-2  it  is  the  dotted  line  joining  the  common 
points  ii  and  a ;  for  1  and  2-2  it  is  the  line  mo ;  for  2  and  4-2,  also  for  2  and  2-2,  it  is  the  line 
joining  the  common  points  £a. 

The  direction  of  the  required  intersection-edges  being  obtained  in  this  way,  they  are  used 
to  construct  the  crystal  itself,  being  transferred  to  it  in  the  usual  way.  In  f.  823  they  have 
been  placed  upon  the  diametral  prism,  and  when  this  process  has  been  completed  for  the 
other  angles,  and,  too,  the  domes  e',  e',  are  added,  the  form  in  f.  824  results. 


ON  THE  DRAWING  OF  TWIN  CRYSTALS. 

In  order  to  project  a  compound  or  twinned  crystal  it  is  generally  necessary  to  obtain  first 
the  axes  of  the  second  individual,  or  semi-individual,  in  the  position  in  which  they  are  brought 
by  the  revolution  of  180°.  This  is  accomplished  in  the  following  manner.  In  f.  825  a  com- 
pound crystal  of  staurolite  is  represented,  in  which  twinning  has  taken  place  (1)  on  an  axis 
normal  to  f -£,  and  (2)  on  an  axis  normal  to  f-f.  The  second,  being  the  more  general  case,  is 
of  the  greater  importance  for  the  sake  of  example.  In  f.  825,  cc',  bb't  aa'  represent  the  rect- 
angular axes  of  staurolite  (c  =  1  -441,  b  —  2'112,  d  =  1).  The  twinning-plane  |-|  (fc  :  —b  :  fa) 


825 


826 


has  the  position  MNR.  It  is  first  n'ecessary  to  construct  a  normal  from  the  centre  0  to  this 
plane.  If  perpendiculars  be  drawn  from  the  centre  O  to  the  lines  MN",  NR,  MR,  they  will  meet 
them  at  the  points  £,  y,  z,  dividing  each  line  into  segments  proportional  to  the  squares  of  the 
adjacent  axes  ;*  or  ~Nx  :  M#  =  ON2  :  OM2.  In  this  way  the  points  x,  y,  z  are  fixed,  and  lines 


*  This  is  true  since  the  axial  angles  are  right  angles.  In  the  Monoclinic  System  two  of 
the  axial  intersections  are  perpendicular,  and  they  are  sufficient  to  allow  of  the  determina- 
tion of  the  point  T,  as  above.  In  the  Triclinic  System  the  method  needs  to  be  slightly 
modified. 


430 


APPENDIX. 


drawn  from  any  two  of  them  to  the  opposite  angles  R,  N,  or  M  will  fix  the  point  T.  A  line 
joining  T  and  O  is  normal  to  the  plane  (MNR  =  f-f ).  Furthermore,  it  is  obvious  that  if  a 
revolution  of  180°  about  TO  take  place,  that  every  point  in  the  plane  MNR  will  remain 
equally  distant  from  T.  Thus,  the  point  M  will  take  the  place  /x(MT  =  T/i),  the  point  V  the 
place  £'  (NT  —  Tj3'),  and  so  on.  The  lines  joining  these  points  /*,  #',  «,  and  the  common 
centre  O  will  be  the  new  axes  corresponding_  to  MO,  NO,  RO.  In  order 
to,  obtain  the  unit  axes  corresponding  to  c,  b,  a  it  is  merely  necessary  to 
draw  through  c  a  line  parallel  to  MT/i,  meeting  /j.0  at  7,  then  707'  is  the 
new  vertical  axis  corresponding  to  cOc',  also  fiOfi  corresponds  to  bQb', 
and  aOa'  corresponds  to  aOa'.  These  three  axes  then  are  the  axes  for 
the  second  individual  in  its  twinned  position ;  upon  them,  in  the  usual  way, 
the  new  figure  may  be  constructed  and  then  transferred  to  its  proper 
position  with  reference  to  the  normal  crystal. 

For  the  second  method  of  twinning,  when  the  axis  is  normal  to  £-*,  the 
construction  is  more  simple.  It  is  obvious  the  axis  is  the  line  0#,  and 
"using  this,  as  before,  the  new  axes  are  found ;  «O«r'  corresponds  to  cOc' 
(sensibly  coinciding  with  bb'\  since  0Af-£  =  134°  21',  and  so  on. 

In  many  cases  the  simplest  method  is  to  construct  first  the  normal 
crystal,  then  draw  through  its  centre  the  twinning-plane  and  the  axis  of 
revolution,  and  determine  the  angular  points  of  the  reversed  crystal  in 
the  principle  alluded  to  above :  that  by  the  revolution  every  point 
remains  at  the  same  distance  from  the  axis,  measured  in  a  plane  at  right 
angle  to  the  axis. 

Thus  in  f.  827  when  the  scalenohedron  has  been  drawn,  since  the  twinning-plane  is  the 
basal  plane,  each  angular  point,  by  the  revolution  of  180°,  obtains  a  position  equidistant  from 
this  plane  and  directly  below  it.  In  this  way  each  angular  point  is  determined,  and  the  com- 
pound crystal  is  completed  in  a  moment. 


Calcite. 


APPENDIX  C. 

TABLES  TO  BE  USED  IN  THE  DETERMINATION  OF  MINERALS. 


TABLE  L 

Minerals  arranged  according  to  their  Physical  and  Blowpipe  Characters. 

THE  following  table  is  intended  especially  for  use  in  instruction  in  Mineralogy.  With  this 
end  in  view  it  is  limited  to  those  species  described  in  full  in  the  body  of  this  work,  and  the 
method  of  arrangement  has  been  made  to  conform  as  nearly  as  possible  to  the  chemical  sys- 
tem of  classification  there  followed.  Table  II.,  on  the  contrary,  is  made  to  embrace  all 
species  whose  crystalline  system  is  known : 

General  Scheme  of  Classification. 

I.  MALLEABLE,  OR  EMINENTLY  SECTILE. 

Many  of  the  native  metals  are  here  included. 

1.  Lustre  metallic. 

2.  Lustre  unmetallic. 

II.  VAPORIZABLE,  OR  B.B.  EASILY  YIELDING  FUMES. 

The  sulphides,  selenides,  etc.,  also  the  sulpharsenides,  sidphantimonides,  etc.,  are  here  in- 
cluded ;  also  some  native  metals. 

Part  I.  WHOLLY  VAPORIZABLE. 

1.  Lustre  unmetallic. 

2.  Lustre  metallic. 

Part  II.  YIELDING  FUMES  READILY,  BUT  NOT  WHOLLY  VAPORIZABLE. 

1.  Lustre  unmetallic. 

2.  Lustre  metallic. — A.  Streak  unmetallic  ;  B.  Streak  metallic. 

III.  NOT  MALLEABLE;  NOT  VAPORIZABLE,  OR  EASILY  YIELDING  FUMES. 

Part  I.  LUSTRE  METALLIC. 

1.  Streak  unmetallic. — A.  Infusible  or  nearly  so  ;  B.  Fusible. 

2.  Streak  metallic. 


a.  Infusible. 

b.  Fusible. 


Part  II.  LUSTRE  UNMETALUC. 
1.  Carbonates. 


432  APPENDIX. 

2.  Sulphates. 

1.  Soluble  in  water,  or  having  taste. 

2.  Insoluble  in  water. 

3.  Chromates. 
4.  Silicates,  Phosphates,  Oxides  (pt.),  etc.,  etc. 

I.  Streak  Colored. 

1.  Infusible,  or  nearly  so. 

2.  Fusible. — A.  Gelatinize  with  acids ;  B.  Do  not  gelatinize. 

II.  Streak  Uncolored. 

1.  Infusible. — A.  Gelatinize  with  acids ;  B.  Do  not  gelatinize. 

2.  Fusible. — A.  Gelatinize  with  acids. 

a  Hydrous;  )8  Anhydrous. 
B.  Do  not  gelatinize. 

a  Hydrous ;  )8  Anhydrous. 


I.  MALLLEABLE  OR  EMINENTLY  SECTILE. 

1.  Lustre  metallic. 

(a)  Yielding  no  fumes. — GOLD;  SILVER;  PLATINUM;  PALLADIUM;  COPPER;  IRON 
(pp.  199-204). 

(#)  Yielding  with  soda  ou  charcoal  a  silver  globule. — ARGENTITE  (p.  213),  and  ACAN- 
THITE  (p.  217),  these  yield  also  sulphurous  fumes. — HESSITE,  Petzite  (p.  216). 

2.  Lustre  unmetallic. 

On  charcoal  a  silver  globule.— CERARGYRITE  (p.  238). 


II.  VAPORLZABLE :  B.B.  easily  yielding  fumes  hi  the  open  tube. 

Part  I.   WHOLLY  YAPORIZABLE  :  readily  passing  away  in  fumes  when  heated  on 

charcoal. 

1.  LUSTRE  UNMETALLIC. 

1.  Fumes  sulphurous;  burning  with  a  flame. — SULPHUR  (p.  206). 

2.  Fumes  antimonial. — VALKNTINITE,  senarmontite  (p.  262). 

3.  Fumes  arsenical. — REALGAR  (p.  209),  color  red;  Orpiment  (p.  209),  color  yellow. 

4.  Fumes  mercurial. — CINNABAR  (p.  218). 

2.  LUSTRE  METALLIC. 

1.  Fumes  sulphurous;  with  also  fumes  of  antimony,  bismuth,  etc.  — STIBNITE  (p.  210); 
BISMUTHINITE  (p  210)  ;  some  tetradymite  (p.  211). 

2.  Fumes  selenial. — CLAUSTHALITE  (p.  214). 

3.  NATIVE  ARSENIC,  ANTIMONY,  BISMUTH,  and  TELLURIUM  (pp.  204,  205).     Some  CIN- 
NABAR (see  above)  has  a  metallic  lustre. 

Part  II.  YIELDING    FUMES    READILY    IN    THE    OPEN    TUBE,  BUT    NOT    WHOLLY 

VAPORIZABLE 

1.  LUSTRE  UNMETALLIC. 

1.  Fumes  sulphurous  alone. — SPHALERITE  (p.  215),  infusible  ;  GREENOCKITE  (p.  220). 

2.  Fumes  sulphurous,  and  (a)  arsenical,  or  ()3)  antimonial ;  yield  a  bead  of  silver  on  char- 
coal— (a)   MlARGYRITE  (p.  227);   PrKARGYRITE  (p.  230).— ()8)  PROUSTITE  (p.  231). 


DETERMINATION    OF   MINERALS.  433 

2.  LUSTRE  METALLIC. 

A.  Streak  Unmetallic. 

1.  Fumes  arsenical. 

a.  On  charcoal  a  magnetic  bead  or  mass,     (a)  In  the  closed  tube  unaltered.  — COB ALTITE 
(p.  224).     (/9)  Do.,  a  red  sublimate  of  arsenic  sulphide.—  ARSENOPYRITE  (p.  225),  color  silver- 
white  ;  TENNANTITE  (p.  284),  color  iron-black ;  GERSDORFFITE  (p.  224),  color  silver- white 
to  steel-gray,  B.  B.  decrepitates.     (7)  Do. ,  a  faint  sublimate  of  arsenous  oxide.  — NICCOLITE 
(p.  220),  color  copper-red. 

b.  With  soda  on  charcoal  a  malleable  bead  of  metallic  lead.— SARTORITE   (p.  228), 
decrepitates  strongly,  G.=5'39  ;  DUFRENOYSITE  (p.  229),  G.  =5 '56. 

c.  Do.,  a  bead  of  silver.— PROUSTITE  (p.  231). 

d.  Do.,  a  bead  of  copper. — DOMUYKITE  (p.  212),  color  tin-white  to  steel-gray. 

2.  Fumes  antimonial. 

Yield  a  silver  globule  on  charcoal. — PYRARGYRITE  (p.  230) ;  MIARGYRITE  (p.  227). 

3.  Fumes  sulphurous. 

a.  Reaction  for  copper  with  borax. — CHALCOPYRITE  (p.  222),  color  brass-yellow ;  BOR- 
NITE  (p.  215),  color  copper-red  to  pinchbeck-brown  on  the  fresh  fracture. 

b.  Yield  a  magnetic  bead  or  mass  on  charcoal,     (a)  Yield  free  sulphur  in  the  closed  tube. 
— PYRITE  (p.  221),  Gr.=4'8-52;  MARCASITE  (p.  225),  G.  =4-7-4-8;  some  linnaeite  (see  be- 
low).    (0)  Unchanged  in  the  closed  tube. — PYRRIIOTITE  (p.  219),  color  bronze -yellow,  mag- 
netic ;  MILLERITE  (p.  219),  color  brass-yellow,  with  borax  a  nickel  reaction  ;  LINNAEITE 
(p.  223),  color  pale  steel-gray,  contains  cobalt. 

B.  Streak  Metallic. 

1.  With  soda  on  charcoal  yield  metallic  copper.       (The  bead  obtained  may  also  be  tested 
with  borax). 

a.  Fumes  sulphurous   alone,     (a)  Contain  only  copper.  —  CHALCOCITE  (p.  217).     (j8) 
Contain  copper  and  silver.  — STROMEYERTTE  (p.  218). 

b.  Fumes  antimonial,  with  or  without  sulphur,     (a)  Contain  copper  and  lead. — BOUR- 
NONITE  (p.  231),  color  steel-gray,  G.  —  5  '7-5  '9.     (/8)  Contain  copper  and  silver. — POLYBASITE 
(p.  235),  color  iron -black.     (7)  TETRAHEDRITB  (p.  233);  some  enargite  (p.  235). 

c.  Fumes  arsenical.—  ENARGITE  (p.  235). 

2.  Yield  lead  or  silver,  but  no  copper  on  charcoal. 

«.  Fumes  sulphurous  alone.     Contain  lead. — GALENITE  (p.  213). 

b.  Fumes   antimonial,    without   arsenic,     (a)  Contain  silver. — DYSCRASITE  (p.  212), 
G.  =9'4-9'8,  color  silver-white  ;  FREIESLEBENITE  (p.  230),  G.  =  6-6  4,  color  steel-gray,  yields 
also  sulphurous  fumes  ; — STEPHANITE  (p.  234),  G.  =G"27,  color  iron-black.     (j8)  Contain  lead. 
— ZINKENITE  (p.  228),  G.   S'30-5'35;  JAMESONITE  (p.  229),  G.=5-5-5'8;  BOULANGERITE 
(p.  232),  G.  =5-75-0. 

c.  Fumes  mercurial. — AMALGAM  (p.  203). 

d.  Fumes  selenial. — CLAUSTHALITE  (p.  214). 

e.  Fumes  telluric,     (a)  Contain  silver  and  gold. — SYLVANITE  (p.  226),  color  steel-gray 
to  silver- white,  brittle  ;  HESSITE,  Petzite  (p.  216),  color  lead-  to  steel-gray,  sectile.     (j8)  Contain 
lead. — NAGYAGITE  (p.  227),  color  black  lead-gray,  foliated. 

3.  Yield  no  lead,  silver  or  copper. 

Molybdenite  (p.  211) ;  Bismuthinite  (p.  210) ;  Tellurium  (p.  205). 

III.  NOT  MALLEABLE ;  NOT  VAPORIZABLE,  NOR  EASILY  YIELDING  FUMES. 

Part  I.  LUSTRE  METALLIC. 

1.  STREAK  UNMETALLIC. 

A.  Infusible,  or  Fusible  with  great  difficulty. 

a.  Reaction  for  manganese  with  borax. 

(o)  Anhydrous.—  PYROLTJSITE  (p.  256),  G.=4'82,  H. =2-2*5,  streak  black  (braunite, 
hausmannite,  p.  255)  ;  FRANKLINITE  (p.  251),  of  ten  in  octahedrons,  G.— 5'07,  H.  =5-5-6-5. 
Streak  dark  reddish-brown  ;  yields  zinc  B.  B. 

(j8)  Hydrous.—  MANGANITE  (p.  258) ;  PSILOMELANE  (p.  260) ;  WAD  (p.  261). 
28 


434:  APPENDIX. 

b.  Reaction  for  iron  :  become  magnetic  upon  ignition  on  charcoal. 

(a)  Anhydrous. — MAGNETITE  (p.  250),  streak  black,  magnetic;  HEMATITE  (p.  246), 
streak  cherry-red.  Contain  titanium. — MENACCANITE  (p.  247),  G.  =4'5-5,  streak  black  to 
brownish-red;  TANTALITE  (p.  337),  G.  =7-8  ;  COLUMBITE  (p.  338),  G.  =5'4-6'5. 

(j8)  Hydrous. — LIMONITE  (p.  258),  streak  yellowish-brown  ;  GOTHITE  (p.  258),  streak 
same  ;  TURGITE  (p.  257),  streak  red. 

c.  Reaction  for  zinc  on  charcoal. — ZINCITE  (p.  244),  streak  orange -yellow. 

'd.  Reaction  for  chromium  with  borax. — CIIKOMITE  (p.  252),  color  black,  streak  brown, 
commonly  in  octahedrons. 

e.  Reaction  f or  fo'^mmw.—  RUTILE  (p.  254);  OCTAHEDRITE  (p.  255);  BROOKITE  (p.  255); 
PKROFSKIT K  (p.  248).  —  Euxenite  (p.  340),  contains  columbium. 

/.  No  reactions  as  above.— YTTROTANTALITE  (p.  339). 

B.    Fusible. 

a.  Reaction  for  iron,  become  magnetic. — ILVAITE  (p.  287),  G.  =3-7-4'2 ;  ALLANITE  (p.  286), 
G.=3-4-2  ;  WOLFRAMITE  (p.  361;,  G.=71-7-5;  SAMARSKITE  (p.  339),  G.  =5 '45-5 -69. 

b.  Reaction  for  copper. — TENORITE  (p.  245) ;  CUPRITE  (p.  244). 

2.  STREAK  METALLIC. 
No  metallic  bead. — GRAPHITE  (p.  208) ;  IRIDOSMINE  (p.  202). 

Part  II.     LUSTRE  UNMETALLIC. 

1.  CARBONATES:  wnen  pulverized  effervesce  (give  off  CO2)  with  hydrochloric  or 
nitric  acid,  sometimes  only  on  the  addition  of  heat  (p.  180).* 

1.  INFUSIBLE. 

a.  No  metallic  reaction,  or  only  traces  ;  assay  alkaline  (p.  183)  after  ignition. 

(a)  Anhydrous. — Effervesce  freely  in  the  mass  in  cold  dilute  acid;  CALCITE  (p.  376), 
O.  — 2'5-2-8;  Alt  AGO  NIT  E  (p.  383),  G.=2'9  ;  BAKYTOCALCITE  (p.  386),  contains  barium.  Effer- 
vescence wanting  or  feeble,  unless  very  finely  pulverized ;  DOLOMITE  (p.  379) ;  MAGNESITE, 
<p.  380). 

(/8)  Hydrous. — HYDROMAGNESITE  (p.  387). 

b.  A  decided  reaction  for  iron  :  become  magnetic  upon  ignition. 

SIDERITE  (p.  381)  ;  ANKERITK  (p.  380).  Also  mesitite,  pistomesite  (p.  381),  and  some 
varieties  of  the  preceding  carbonates. 

c.  A  decided  reaction  for  manganese  with  borax. 

RHODOCIIROSITE  (p.  381).     Also  some  varieties  of  the  preceding  carbonates. 

d.  Reaction  for  zinc  on  charcoal. 

(a)  Anhydrous. — SMITHSONITE  (p.  382).     (£)  Hydrous. — HYDROZINCITE  (p.  388). 

2.  FUSIBLE. 

a.  No  metallic  reaction,  or  only  traces  ;  assay  alkaline  after  fusion. 

(a)  Anhydrous. — WITHERITE  (p.  384),  G.  =4'3,  B.B.  a  green  flame  (baryta);  STRON- 
TIANITE  (p.  384),  G.=3-6-3'7,  B.B.  a  strontia-red  flame. 

(|3)  Hydrous.—  GAY-LUSSITE  (p.  387);  TRONA  (p.  386). 

b.  Reaction  for  lead  on  charcoal. 

CERUSSITE  (p.  $85) ;  PHOSGENITE  (p.  386),  contains  lead  chloride ;  LEADHILLITE 
(p.  386),  contains  lead  sulphate. 

c.  Reaction  for  copper  with  borax. 

Hydrous.—  MALACHITE  (p.  389),  color  green  ;  AZURITE  (p.  389),  color  azure-blue. 

d.  Reaction  for  bismuth  on  charcoal. 

Hydrous. — BISMUTITE  (p.  390). 

*  Nitric  acid  is  needed  only  in  the  case  of  lead  salts  (cerussite,  phosgenite,  leadhillite).  In 
addition  to  the  proper  carb  mates,  also  leadhillite  and  cancrinite  o.ff ervesce  with  acid,  and 
with  many  minerals  effervescence  may  be  caused  by  a  mechanical  admixture  of  calcite  (e.g., 
wollastonite),  or  some  other  carbonate  (e.g.  lanarkite). 


DETERMINATION   OF   MINERALS.  4:35 

2.  SULPHATES  :  Yield  a  sulphide  with  soda  on  charcoal  (p.  187),*  which  when  moist- 
ened blackens  a  surface  of  polished  silver. 

SOLUBLE  IN  WATER  :  having  taste. 

a.  GLAUBERITE  (p.  369) ;  MIRABILITE  (p.  370) ;  POLYHALITE  (p.  371) ;  EPSOMITE  (p.  372); 
ALUMS  (p.  373). 

b.  Copperas  group  :  Vitriols. — CHALCANTHITE,  etc.  (p.  372). 

2.  INSOLUBLE  IN  WATER  ;  having  no  taste. 

a.  Yield  no  metallic  bead.     Fusible  ;  assay  alkaline  after  fusion. 

(a)  Anhydrous. — BARITE  (p.  365),  G.=4'3-4'7,  a  yellowish-green  flame  B.B.;  CELES- 
TITE  (p.  366),  G.=3'92-3'97,  a  strontia-red  flame  B.B.;  ANHYDRITE  (p.  367),  G.  =2-9-2 '99, 
a  reddish-yellow  flame. 

(p)  Hydrous:  GYPSUM  (p.  370),  H=l'5-2,  G.— 2'3. 

b.  Reaction  for  aluminum  ;  a  blue  color  with  cobalt  solution  after  ignition. 

Hydrous  :  ALUMINITE  (p.  373). 

c.  Reaction  for  lead  on  charcoal. 

Fusible. — ANGLESITE  (p.  367)  ;  LEADHILLITE  (p.  368),  contains  lead  carbonate. 

d.  Reaction  for  copper  with  borax. 

BROCHANTITE  (p.  374);  LINARITE  (p.  374). 

e.  Reaction  for  iron  :  become  magnetic  after  ignition  on  charcoal. 

COPIAPITE  (p.  373). 

3.  CHROMATES :   Afford  a  chromium  reaction  with  borax  (p.  186).     All  brightly  col- 
ored, and  having  a  colored  streak. 

CROCOITE  (p.  363),  color  hyacinth-red,  streak  orange-yellow ;  PHOJJNICOCHROITE, 
(p.  364),  color  cochineal-  to  hyacinth-red,  streak  brick-red;  VAUQUELINITE  (p.  364),  color 
green  to  brown,  streak  greenish  or  brownish. 

4.  SILICATES,  PHOSPHATES,  OXIDES  (in  part),  etc. 
I.   STREAK  COLORED  :  having  a  decided  color. 

1.  INFUSIBLE,  OR  FUSIBLE  WITH  GREAT  DIFFICULTY. 

a.  Reaction  for  iron,  magnetic  after  ignition  in  R.F. 

(a)  Anhydrous. — HEMATITE  (p.  246),  streak  cherry-red. 

()8)  Hydrous. — LIMONITE  (p.  258),  streak  yellowish-brown ;  GOTHITE  (p.  258),  streak 
same;  TURGITE  (p.  257),  streak  red,  decrepitates  B.B. 

b.  Reaction  for  manganese  with  borax. 

Hydrous. — WAD  (p.  261);  PSILOMELANE  (p.  260). 

c.  Reaction  for  zinc,  with  cobalt  solution. 

ZINCITE  (p.  244)  ;    streak  orange -yellow.  » 

d.  Reaction  for  copper :  yield  a  metallic  bead  with  soda  on  charcoal. 

Hydrous. — DIOPTASE  (p.  279),  color  emerald-green. 

e.  Reaction  for  titanium :  with  metallic  tin  on  evaporation  a  violet  color  to  the  hydro- 
chloric acid  solution,  sometimes  after  fusion  with  potassium  bisulphate. 

RUTILE  (p.  254),  G.=4-2;  WABWICKITE  (p.  360),  G.=r3-3,  moistened  with  sulphuric 
acid  gives  a  green  flame  B.B.  (boron). — Some  Pyrochiore  (p.  337) ;  and  Perofskite  (p.  248). 
/.   Reaction  for  tin  :  yields  the  metal  with  soda  on  charcoal. 

CA8SITERITE  (p.   253),  G.  =  6'4-7'l. 

g.  Not  included  in  the  above. 

(a)  Phosphates  :  moistened  with  sulphuric  acid  give  a  bluish-green  flame  B.B. — MONA- 
ZITE  (p.  346),  G.  =4-9-5 -26;  XENOTIME  (p.  342),  G.=r4'45-4-56. 

(j8)  PYROCHLORE,  Microlite  (p.  337),  G.4-2-4'35  ;  FERGUSONITE  (p.  340). 

*  Note  the  precaution  on  p.  187  ;  it  may  be  remarked  in  addition  that,  in  the  case  of  a  sul- 
phate, the  reaction  is  generally  so  decided  that  there  can  be  no  ambiguity,  even  when  the 
gas  contains  a  little  sulphur.  In  all  cases  the  soda  on  charcoal  should  be  first  tested  alone. 


436  APPENDIX. 

2.  FUSIBLE  WITHOUT  VERY  GREAT  DIFFICULTY. 

A.   Gelatinize  with  Acid  (p.  181). 

Give  a  reaction  for  iron. 

ILVAITE  (p.  287),  yields  little  or  no  water,  TL  =5-5-6,  G.— 3'7-4'2,  streak  black; 
HISINGERITE  (p.  332),  yields  much  water,  H.=3,  G.=3.045,  streak  yellowish-brown; 
ALLANITE  (p.  286),  H.=5-5-6,  G.3-4'2,  streak  gray. 

B.  Do  not  Gelatinize  with  Acid. 

1.  Arsenates :  give  arsenical  fumes  on  charcoal ;  after  roasting  yield  metallic  reactions  as 
follows : 

a.  Reaction  for  iron  :  become  magnetic  after  ignition. 
PHARMACOSIDERITE  (p.  354),  color  olive-green  to  yellowish-brown,  etc. 

b.  Reaction  for  cobalt  with  borax. 
ERYTHKITE  (p.  350),  color  rose-red. 

c.  Reaction  for  copper  with  borax ;  also  give  a  green  flame  BB. 

Hydrous. — OLIVENITE  (p.  351),  G.4'1-4'4,  color  olive-green  to  brown;  LIROCONITE  (p. 
352),  G.2-88-2'98,  color  sky-blue  to  verdigris-green;  CLINOCLASITE  (p.  352),  G.=3'6-3'8, 
color  dark-green  (some  libethenite,  see  below). 

2.  No  arsenical  fumes ;  reaction  for  iron :  become  magnetic  after  fusion. 

a.  Anhydrous. — Reaction  for  titanium:  SCHORLOMITE  (p.  315),  H.  =7-7 '5,  G.=3-862, 
massive. — Reaction  for  tungsten:  WOLFRAMITE  (p.  361),  H.  =5-5 '5,  G. =71-7 '55. — Reac- 
tion for  manganese  :  TRIPLITE  (p.  347),  H.  =3'44-3 '88,  G.  =4-5 '5,  colors  the  flame  bluish- 
green. — Structure  micaceous  :  LEPIDOMELANE  (p.  291). 

b.  Hydrous.—  Give  a  bluish-green  flame  B.B.  :  VIVIANITE  (p.  349),  H.  =1*5-2,  G.  =. 
2-58-2-68,  streak  colorless  to  indigo-blue  (on  exposure) ;  DUFRENITE  (p.  356),  H.=3  5-4,  G. 
=3 '2-3 '4,  streak  siskin-green. 

IV  No  arsenical  fumes  ;  reaction  for  copper  with  borax,  yield  an  emerald-green  flame  B.B. 
(a)  Anhydrous.  —  C UPRITE  (p.  244)  ;  TENORITE  (p.  245),  color  steel-gray  to  black. 
()8)  Hydrous. — Structure  micaceous;  TORBERNITE  (p.  356),  H.  =2-2-5,  G.  =3-4-3 -6. 
— LIBETHENITE  (p.  351),  H.=4,  G.  =3'6-3-8;  PSEUDOMALACHITE  (p.  352),  H.=4'5-5,  G.  = 
4-4-4.    ATACAMITE  (p.  239).     H.=3-3'5.     G.=3'8. 

II.  STREAK  UNCOLORED  :  sometimes  slightly  grayish ,  yellowish,  etc. 

1.  INFUSIBLE,  OR  FUSIBLE  WITH  MUCH  DIFFICULTY. 

A.    Gelatinize  with  Acid  forming  a  stiff  JeUy. 

a.  Reaction  for  iron  with  the  fluxes. 

CHRYSOLITE  (p.  278) ;  CHONDRODITE,  HUMITE  (pp.  304-307),  yields  fluorine. 

b.  Reaction  for  zinc  on  charcoal,  after  being  heated  with  soda. 

(a)  Hydrous. — CALAMINE  (p.  317). 
($    Anhydrous. — WILLEMITE  (p.  279). 

c.  Reaction  for  aluminum  ;  a  blue  color  with  cobalt  solution  after  ignition. 

ALLOPHANE  (p.  319).  amorphous. 

d.  Reaction  for  magnesium  :  pink  color  with  cobalt  solution  after  ignition. 

SEPIOLITE  (p.  327),  in  soft,  white,  compact  masses. 

B.  Do  not  form  a  perfect  Jelly  with  Acid. 
1.  Hydrous. 

a.  Reaction  for  aluminum  :  a  blue  color  with  cobalt  solution  after  ignition. 

1.  Phosphates  :  give  a  bluish-green  flame  B.B.,  especially  after  being  moistened  with 
sulphuric  acid. — WAVELLITE  (p.  354),  color  white  to  green  to  black ;  LAZULITE  (p.  353), 


DETERMINATION    OF   MINEKALS.  437 

color  azure-blue,  with  borax  an  iron  reaction ;  TURQUOIS  (p.  355),  color  sky-blue  to  apple- 
green,  with  borax  a  copper  reaction. 

2.  Hydrous  silicates. — Structure  micaceous  :  MARGARITE  (p.  335),  yields  much  water  ; 
also  some  hydrous  micas  (see  p.  331).     The  CHLORITES  (see  p.  333,),  are  difficultly  fusible. — 
KAOLINITE  (p.  329)  usually  compact,  soft,  unctuous  ;   PYROPHYLLITE  (p.  327),  soft,  yields 
much  water. 

3.  Oxides.— GIBBSITE  (p.  260),  H.  =  2 '5-3-5,  usually  in  stalactitic  forms;   DIASPOBE 
(p.  257),  H.  =6 '5-7,  in  crystals,  scales,  and  foliated,  usually  decrepitates  B.B. 

b.   Reaction  for  magnesium :  a  pink  color  with  cobalt  solution  after  ignition. 

BRUCITE  (p.  259),  soluble  in  acids  ;  TALC  (p.  326),  yields  water  only  on  intense  igni- 
tion.    Also  some  serpentine  (see  below). 
6.  No  Reactions  as  above. 

OPAL  (p.  266),  H.=6-7.— SEBPENTINE  (p.  328),  H.=25-4;  CHLOBITOID  (p.  336), 
H.  =5-5-6  ;  GENTHITE  (p.  329),  yields  a  reaction  for  nickel  with  borax.— CHBYSOCOLLA  (p. 
316),  H.=2-4,  colors  the  flame  emerald-green  (copper,. 


a.  Reaction  for  aluminum  :  (When  of  great  hardness,  pulverizing  is  necessary). 

(a)  Decomposed  by  acids. — LEUCTTE  (p.  296)  H.=5-5-6. 
(0)  Structure  eminently  micaceous. — MUSCOVITE  (p.  291). 
(7)  COBUNDUM  (p.  245),  H.  =9,  G.  =4,  rhombohedral. 
CHBYSOBEBYL  (p.  252),  H.=8'5,  G.  =3 -7,  color  green. 
TOPAZ  (p.  310),  H.=8,  G.=3.5,  in  prisms  of  124°,  cleavage  basal  perfect. 
RUBELLITE  (p.  308),  H.  =7.5,  G.  3,  in  three-  or  six-sided  prisms,  color  violet,  rose-red, 
reaction  for  boron  (p.  189). 

(  ANDALUSITE  (p.  309),  H.=7'5,  G.=3'2,  in  prisms  of  93°. 

•j  FIBBOLITE  (p.  309),  H.  -6-7,  G.  3 '2,  brilliant  diagonal  cleavage. 

(  CYANITE  (p.  310),  H.=5-7,  G.=3'6,  usually  in  bladed  crystals,  color  blue  to  gray. 

b.  Reaction  for  magnesium  :  a  pink  color  with  cobalt  solution  after  ignition. 

TALC  (p.  326),  soft,  foliated,  yields  water  upon  intense  ignition. 
ENSTATITE  pt.  (p.  268),  H.=5'5.  cleavage  prismatic  93°. 
SPINEL  pt.  (p.  249),  H.=8,  commonly  in  octahedrons. 

c.  Reaction  for  tin :  metallic  globule  with  soda  in  charcoal. 

CASSITEBITE  (p.  253),  G.=6'4-71.     Also  some  Pyrochlore  (p.  337). 

d.  No  reactions  as  above. 

1.  Hardness  7  or  above  7. 

SPINEL  (p.  249),  H.=8,  G.=3'5-41,  occurs  in  octahedrons. 

GAHNITE  (p.  250),  H.=7'5-8,  G.=4'4-4'9,  9ctahedral,  when  mixed  with  borax  gives  a 
zinc  coating  on  charcoal. 

BEBYL  (p.  277),  H.  =7-5-8,  G.  =2 '6-2 -7,  always  in  hexagonal  prisms. 

PHENACITE  (p.  279),  H.=7-5-8,  G.=3. 

OUVABOVITE  (p.  282),  H.=7'5,  G.  =3'5,  color  green,  chromium  reaction. 

ZIRCON  (p.  282),  EL=7'5,  G.=4'05-4-75,  zirconia  reaction  (p.  191),  often  in  square 
prisms. 

STAUBOLITE  (p.  314),  H.=7,  G.  =3-4-3-8,  always  crystallized,  /A 7=123°. 

IOLITE  (p.  289),  H.  =7-7-5,  G.=2'6,  color  blue,  lustre  glassy. 

QUARTZ  (p.  262),  H.=7,  G=2'6,  and  TRIDYMITE  (p.  266),  G.=2'3. 

2.  Hardness  below  7. 

(a)  Give  a  bluish-green  flame  when  moistened  with  sulphuric  acid ;  XENOTIME 
(p.  342) ;  MONAZITE  (p.  346) ;  APATITE  (p.  342). 

(0)  Reaction  for  titanium. — RUTILE  (p.  254) ;  BROOKITE  (p.  255) ;  OCTAHEDBITE 
(p.  255),  always  in  square  octahedrons ;  PEROPSKITE  (p.  248). 

(7)  Reaction  for  tungsten. — SCHEELITE  (p.  362),  H.  =6,  G.  =4*5-5. 

(8)  Not  included  in  the  above  :  ENSTATITE  (p.  268) ;  Diallage  (p.  271) ;  ANTHOPHYL- 
LITE  (p.  273). 

B.  FUSIBLE. 

1.   Gelatinizing  with  Acid  :  forming  a  stiff  Jetty  upon  Evaporation. 


438  APPENDIX. 

1.  Hydrous. 

a.  Hardness  5  or  above  5. 

DATOLITE  (p.  312),  in  glassy  crystals,  also  rarely  massive,  never  fibrous,  fuses  with  a 
green  flame  (boron). 

NATROLITE  (p.  320),  G.=2'17-2-25,  fuses  quietly  and  easily  to  a  colorless  glass. 

SCOLECITE  (p.  321),  THOMSONITE  (p.  320),  on  fusion  often  curl  up  in  worm-like 
forms. 

b.  Hardness  below  5. 

GMELINITE  (p.  323),  H.  =4'5,  in  hexagonal  or  rhombohedral  crystals. 
PHILLIPSITE  (p.  323),  H.  =4-4 '5,  in  twinned  crystals. 
LAUMONTITE  (p.  316),  H.  =3'5,  becomes  opaque  on  exposure. 

PECTOLITE  and  ANALCITE  are  decomposed  by  acid  with  the   separation  of   gelatinous 
silica,  but  do  not  form  a  stiff  jelly. 


2.  Anhydrous. 

a.  With  hydrochloric  acid  give  off  sulphuretted  hydrogen. 

DANALITE  (p.  280),  with  soda  on  charcoal  gives  a  zinc  coating,  color  flesh-red  to  gray. 
HELVITE  (p.  280).  manganese  reaction  with  borax,  color  yellow. 

b.  With  soda  on  charcoal  a  sulphur  reaction. 

HAUYNITE   p.  296),  color  sky-blue. 

c.  SODALITE  (p.  295),  reaction  for  chlorine. 

WOLLASTONITE  (p.  269),  color  white,  lustre  vitreous. 
NEPHELITE  (p.  294),  hexagonal. 


2.  Do  not  form  a  perfect  Jelly  with  Hydrochloric  Acid. 

Hydrous. 

1.  Structure  eminently  micaceous. 

Chlorites  :  PENNINITE  (p.  333) ;  RIPIDOLITE  (p.  334) ;  PROCHLORITE  (p.  335) ;  lamina 
tough  but  not  elastic,  colors  green  to  black  ;  only  partially  attacked  by  acid. 

Vermiculites :  JEFFERISITE  (p.  333. );  also  pyrosclerite,  etc.,  colors  mostly  brown- 
yellow,  also  green,  B.B.  exfoliate  largely,  decomposed  by  acid  with  the  separation  of  silica. 

LEPIDOMELANE  (p.  291),  color  black,  yields  a  magnetic  globule. 

AUTUNITE  (p.  357),  H.=2-2'5,  color  bright  yellow. 

FAHLUNITE  (p.  331),  has  a  more  or  less  distinct  micaceous  structure. 

2.  Structure  not  micaceous. 

1.  Reaction  for  iron  :  leave  a  magnetic  residue  on  charcoal. 

(a)  Arsenates:  give  arsenical  fumes  on  charcoal.  —  SCORODITE  (p.  353),  orthorhombic  ; 
PHARMACOSIDERITE  (p.  354),  isometric. 

(/8)  Phosphates  :    give  a  bluish-green  flame  after  moistening  with  sulphuric  acid. — 
CHILDRENITE  (p.  355),  reacts  for  manganese,  fuses  only  on  the  edges,  H.  =4'5-5. 
VIVIANITE  (p.  349),  H.  =1  '5-2,  fuses  easily  to  a  magnetic  globule. 

2.  Reaction  for  arsenic  on  charcoal. 
PHARMACOLITE  (p.  348). 

3.  Borates  :  give  a  deep-green  flame  after  moistening  with  sulphuric  acid. 

BORAX  (p.  359);  BORACITE  (p.  359) ;  ULEXITE  (p.  359);  SUSSEXITE  (p.  358). 

4.  Not  included  above. 

(a)  Hardness  5,  or  above  5  (apatite =5). 
PREHNITE  (p.  318),  H.=6-6'5,  color  apple-green  to  white. 
ANALCITE  (p.  321),  H.  =5-5-5,  fuses  quickly  to  a  clear  glass. 
PECTOLITE  (p.  315),  H.  =5,  usually  in  aggregations  of  acicular  crystals. 
APOPHYLLITB  (p.  318),  H.=4'5-5,  B.B.  a  violet-blue  flame. 


DETERMINATION   OF   MINERALS.  439 

Hardness  below  5. 


. 

FINITE  (p.  330),  H.  =2'5-3 '5,  compact. 

PACHNOLITE  (p.  243),  H.  =2-4,  yields  fluorine. 

CHABAZITE  (p.  3^2),  H.=4-5,  rhombohedral. 

APOPHYLLITE  (p.  318),  H.  =4-5-5,  tetragonal. 

HARMOTOME  (p.  324),  H.  =4*5,  usually  in  compound  crystals. 

STILBITE  (p.  324),  H.=3'5-4. 

HEULANDITE  (p.  325),  H.=3'5-4. 


Anfiydrous. 

1.  Yield  metallic  lead  with  soda  on  charcoal. 

PYROMORPIIITE  (p.  344),  color  green,  gives  a  bluish-green  flame  on  fusion. 
MIMETITE  (p.  344),  color  yellow  to  brown,  yields  arsenical  fumes  on  charcoal. 
VANADINITE  (p.  344),  color  brownish-yellow  to  reddish-brown,  with  borax  R.F.  an 
emerald  green  bead. 

WULFENITE  (p.  362),  color  bright  yellow  to  red,  reaction  for  tungsten. 

2.  Reaction  for  fluorine,  with  sulphuric  acid. 

(a)  Give  a  bluish-green  flame  after  moistening  with  sulphuric  acid. 

AMBLYGONITE  (p.  347),  gives  a  lithia-red  to  the  flame. 

TRIPLITE  (p.  347),  a  strong  manganese  reaction. 

WAGNERITE  (p.  346 1,  color  yellow  to  grayish. 

(0)  FLUORITE  (p.  241),  cleavage  octahedral,  perfect. 

CRYOLITE  (p.  242),  fusible  in  the  flame  of  a  candle. 

LEPIDOUTE  (p.  292),  color  pink,  structure  micaceous. 

3.  Reaction  for  lithia  :  give  a  purple-red  color  to  the  flame. 

SPODUMENE  (p.  273),  H.=6'5-7.  G.  =3 -13-3-19. 

TRIPHYLITE  (p.  347),  H.  =5,  G.  =3-54-3'6,  gives  a  bluish-green  color  to  the  extremity 
of  the  flame. 

The  mica  lepidolite,  and  also  some  biotite,  give  a  lithia  flame. 

4.  Reaction  for  iron  with  the  fluxes. 

VKSUVIANITE  (p.  283),  tetragonal,  H.=6'5. 
EPIDOTE  (p.  285),  monoclinic,  H.=6'7. 
GARNET  pt.  (p.  280),  is  isometric,  H.  =6 '5-7-5. 
LEPIDOMELANE  (p   291),  structure  micaceous. 
HYPERSTHENE  (p.  268),  orthorhombic. 
Here  fall  also  dark-colored  varieties  of  AMPHIBOLE  (p.  274),  and  PYROXENE  (p.  270). 

5.  Reaction  for  manganese  with  borax. 

RHODONITE  (p.  272),  color  usually  rose-red. 
SPESSARTITE  (manganese  garnet,  p.  282). 

6.  Reaction  for  titanium. 

TIT  AN  ITS  (p.  313). 

7.  Reaction  for  tunyxten. 

SCIIEELITK  (p.  362). 

8.  Not  included  in  the  above. 

HALITE  (p.  237),  SYLVITE  (p.  238),  soluble  in  water. 

MICAS  (pp.  289-292),  structure  eminently  micaceous.      • 

APATITE  (p.  342),  H.  =5,  G.  ^2'9-3-25.  a  bluish-green  flame  after  moistening  witn 
sulphuric  acid. 

PYROXENE  (p.  270),  H.  =5-6,  G.  =3  2-3  5,  monoclinic,  angle  of  prism  93°. 

AMPHIBOLE  (p.  274),  H.=5-6,  G.  =2 -9-3 '4,  monoclinic,  angle  of  prism  (cleavage 
perfect)  124|°. 

SCAPOLITES  (pp.  293,  294),  H.=5-6'5,  G.=2'5-2  8,  tetragonal;  B  B.  fuse  with  intu- 
mescence to  a  blebby  glass. 

ZOISITE  (p.  286),  H.=6-6-5,  G.=3-l-3'38,  orthorhombic  ;  B.B.  swells  up  and  fuses  to 
a  blebby  glass. 

FELDSPARS  (pp.  S97  to  304),  H.=6-7,  G.  =2 "6-2-8,  cleavage  in  two  directions  at  right 
angles  or  nearly  so  ;  B.B.  fuse  quietly  to  a  clear  glass. 

AXINITE  (p.  288),  H.=6'5-7,  G.=3"27;  B  B.  reaction  for  boron 

TOURMALINE  (p.  307),  H.  =7,  G.  =2-9-3'3  ;  no  distinct  cleavage,  commonly  in  three- 
or  six-sided  prisms  ;  B.B.  reaction  for  boron. 

GARNET  (p.  280),  H.=6'5-7'5,  G.=3'15-4'3,  isometric. 


440 


APPENDIX. 


TABLE     II. 

Minerals  Arranged  According  to  their    Crystallization. 

The  following  table  contains  the  names  of  all  distinct  species  whose  Crystalline  System  is 
known.  For  convenience,  however,  the  names  of  those  which  are  described  in  detail  in  the 
body  o£  the  work  are  printed  in  small  capitals.  The  species  are  arranged  according  to  theii 
specific  gravities. 

I.  CRYSTALLIZATION  ISOMETRIC. 
A.  LUSTRE  UNMETALLIC. 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

Sal  Ammoniac  (p  238) 

1*53 

1  -5-2 

Periclasite  (p   245)  . 

3-67 

6 

Alum  (p   373). 

1  -56-2 

2-2-5 

Arsenolite  (p.  262)  .  .  . 

3-70 

1-5 

Faujasite  (p.  322)  

1-92 

5 

Nantokite  (p.  238)  

3-93 

2-2-5 

SYLVITE  (p  238) 

1-9-2 

2 

SPINEL  (p   249) 

3-5-4-1 

8 

HALITE  (p  237). 

21-2-26 

2-5 

Hercynite  (p.  250)   

3-9-3-95 

7-5-8 

Chlorocalcite  (p   238) 

Alabandite  (p  215) 

3-95-4 

3-5-4 

Kremersite  (p   239) 

Percylite  (p  240)     .      . 

2-5 

SODALTTE  (p.  295).  .  .  . 

2-14-2-4 

5-5-6 

SPHALERITE  (p.  215)  .  . 

3-9-42 

3-5^ 

ANALCITE  (p.  321)  

2-2-2-29 

5-5-5 

PEROPSKITE  (p.  248).  .  .  . 

4-04 

5-5 

Nosite  (p    296) 

2  25-2-4 

5-5 

Chrompicotite  (p   252) 

4-12 

8 

Ralstonite  (p.  243)  

2-4 

4-5 

Tritomite  (p   318)  

3-9-4-7 

5-5 

HAUYNITE  (p.  29(5)  

2-4-2-5 

5-5-5 

PYROCIILORE  (p.  337)... 

4-2-4-35 

5-5-5 

LEUCITE  (p  296).     . 

2-4-2-56 

5  -5-6 

Pyrrhite  (p  337)  

6 

Oldhamite  (p  213) 

2-58 

4 

GAHNITE  (p    250) 

4-4-6 

7-5-8 

Pollucite  (p.  277)  

PHARMACOSIDERITE    (p. 
354) 

2-9 
2-9-3 

6-5 
2'5 

Thorite  (p.  318)  
Senarmontite  (p.  262)... 
Embolite  (p   238) 

4-3-5-4 
5-2-5-3 
5-3-5-4 

4-5-5 
2-2-5 
1-1  -5 

BORACITE  (p  359) 

2-97 

7 

Microlite  (p.  337) 

5-5 

FLUORITE  (p.  241).  .    . 

3-19 

4 

CERARGYRITE  (p.  238).. 

5-5-5 

1-1-5 

HELVITE  (p.  280)  

31-3-3 

6-6-5 

iHuantajayite  (p.  237).  .  . 

GARNET  (p.  280)       .   .  . 

3-15-4-3 

6'5-7'5 

Bromyrite  (p  238) 

5-8-6 

2-3 

DANALITE  (p  280) 

3-43 

5'5  6 

CUPRITE  (p  244) 

5-8-615 

3-5-4 

Hauerite  (p.  222)  

3-46 

4 

Eulytite  (p.  280)  

5-9-6 

4-5 

DIAMOND  (p  206) 

3-53 

10 

Bunsenite  (p   245)     .... 

6-4 

5-5 

B.  LUSTRE  METALLIC. 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

Cubanite  (p.  223)       

4-03-4-2 

4 

SMALTITE  (p.  223)  

6-4-7-2 

5-5-6 

PEROFSKITE  (p.  248)  
CHROMITE  (p.  252)  
TENNANTITE  (p  234) 

4-04 
4  -3^-6 
4-4-4-5 

5-5 
5-5 
3-5-4 

Skutterudite  (p.  224)  .  .  . 
Polyargyrite  (p.  235).  .  .  . 
Laurite  (p   225) 

6-7-6-8 
6-97 
6-99 

6 
2-5 

7  (above) 

Binnite  (p  229) 

4-48 

4-5 

Uraninite  (p.  252)     .  . 

6-4-8 

5-5 

Magnesioferrite  (p.  251). 
Jacobsite  (p.  250)  

4-6 

4-75 

6-6-5 
6 

ARGENTITE  (p.  213).  .  .  . 
GALENITE  (p.  213)  

7-2-7-4 
7-25-7-7 

2-2-5 
2-5-3 

Corynite  (p   225) 

4-99' 

4-5-5 

IRON  (p.  204)  

7-3-7-8 

4-5 

BORNITE    (p    215)  .... 

4-4-5-5 

3 

Metacinnabarite  (p.  219). 

7-5-7-7 

3 

TETRAHEDRITE  (p.  233). 

LlNNyEITE   (p.  223)  

PYRITE  (p  221) 

4-5-5-1 

4-8-5 
4-8-5-3 

3-4-5 
5-5 
•66-5 

CLAUSTHALITE  (p.  214)  . 
Naumannite  (p.  213).  .  .  . 
Altaite  (p   215) 

7-6-8-8 
8-0 
8-16 

2-5-4 
2-5 
3-3-5 

MAGNETITE  (p.  250) 

4-9-5-2 

5  -5-6  '5 

COPPER  (p.  203)  

8-84 

2-5-3 

FRANKLINITE  (p  251) 

5-07-5-09 

5-5  6'5 

SILVER  (p  201) 

10-1-111 

2-5-3 

Julianite  (p.  234)  

5-12 

soft 

PALLADIUM  (p.  202)  

11-3-11-8 

4-5-5 

Griinauite  (p   215) 

5-13 

4  -5 

AMALGAM  (p.  203)  

14 

3-3-5 

GERSDORFFITE  (p.  224). 
COBALTITE  (p.  224)  

XJLLMANNITE    (p.  225).  . 

5-6-6-9 
6-6-3 
6-2-6-5 

5-5 
5-5 
5-5-5 

GOLD  (p.  199)  
PLATINUM  (p.  201)  
Platiniridium   (p.   202).. 

15-6-19-5 
16-19 
22-6-23 

2-5-3 
4-4-5 
6-7 

DETERMINATION    OF    MINERALS. 


441 


The  commonly  occurring  forms  of  some  of  the  Isometric  minerals  are  as  follows : 
1. —  Octahedrons. — Alum;  Cbromite  ;   Cuprite;  Diamond;  Franklinite  ;  Magnetite;  Micro- 
lite  ;  Pyrochlore  ;  Ralstonite  ;  Spinel  (incl.  hercynite,  etc.).     Also  Laurite  ;  Pyrrhite  ;  Senar- 
montite,  and  less  commonly  Galenite  ;  Fluorite. 

2.  Cubes. — Boracite;    Cerargyrite ;    Fluorite;    Galenite;    Halite;    Percylite;    Perofskite  ; 
Pharmacosiderite ;  Pyrite  ;  Sylvite. 

3.  Dodecahedrons. — Amalgam;  Cuprite;  Garnet;  Magnetite. 

4.  Trapezohedrons. — G-arnet ;  (?)  Leucite  ;   (?)  Analcite. 

5.  Pyritohedrons. — Cobaltite  ;  Gersdorffite  ;  Hauerite  ;  Pyrite. 

The  CLEAVAGE  of  Halite,  Sylvite,  Periclasite,  Galenite  is  eminently  cubic  ; — of  Fluorite, 
Magnetite,  Diamond  eminently,  octahedral ; — of  Sphalerite,  eminently  dodecahedron. 

II.  CRYSTALLIZATION  TETRAGONAL. 
A.  LUSTRE  UNMETALLIC. 


! 

Spec.  Gravity  Hardness. 

Spec.  Gravity 

Hardness. 

Mellite  (p   390) 

1  -55-1  -65 
23-2-4 
2-38 
2-4-2-56 
2-5-2-9 
2-63-2-8 
2-6-2-74 
2-7 
27-2-9 
2-97 
2-9-3-07 
2-9-3-1 
3-0 
32 
3-35-3-45 
34-3-6 
3-74 

2-2-5 
4-5-5 
2-5-3 
5-5-6 
6 
5-6 
5.5-6 
4-4-5 
4 
5 
5-5-6 
5 

2-2-5 
6-5 
2-2-5 
3-3-5 

Adelpholite  (p.  341)  

OCTAHEDRITE  (p.  255).  . 

RUTILE  (p.  254)  

3-8 
3-8-3-95 
4-18-4-25 
4-45-4-56 
4-4-75 

4-7 
5-94 
5-9-6-08 
6-6-3 
6-48 
6-4-71 
6-7-01 

7-2 
7-9-8-13 

3-5-4-5 
5-5-6 
6-6-5 
4-5 

7-5 

5-6 
4-5-5 
4-5-5 
2-75-3 
1-2 
6-7 
2-75-3 
3-4 
275-3 
2-75-3 

APOPHYLLITE  (p.  318).. 
Lceweite  (p  372)  

LEUCITE  (p.  296). 

XENOTIME  (p.  342)  

Sarcolite  (p   294) 

i  ZIRCON  (p  282)     . 

WERNERITE  (p.  294)  
MEIONITE  (p  293)     .... 

Azorite  (p.  337)  

Romeite  (p.  348)  

Edingtonite   (p.  319)  
Chiolite  (p.  242) 

Monimolite  (p.  348)  

SCHEELITE    (p.   362)  
iPlIOSGENITE    (p.   386).  .  . 

Calomel  (p  238) 

Sellaite  (p  242)   

Gehlenite  (p   309) 

Mellilite  (p  284) 

CASSITERITE  (p.  253)... 
WULFENITE  (p.  362).  ... 
Eosite  (p  363)      

Chodneffite  (p.  242).    .  .  . 

Zeunorite  (p   357) 

VESUVIANITE  (p.  283)  .  . 

TORBERNITE  (p.  356)  .  .  . 

Kochelite  ''p.  341) 

Matlockite  (p.  240)  

Stolzite  (p   362)  

B. 

LUSTRE 

METALLIC. 

Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

CHALCOPYRITE  (p.  222)  . 
Stannite  (p.  223)       

4-1-4-3 
4-3-4-5 

3-5-4 

4 

FERGUSONITE  (p.  .340)  .  . 
NAGYAGITE  (p  227) 

5-84 
6-85-7-2 

5-8-6 
1-1-5 

Hausmannite  (p.  255)  .  .  . 

4-72 

5-5-5 

Tapiolite  (p.  339)  

7-36 

6 

Braunite  (p.  255)        .    .  . 

4-75-4-8 

6-6-5 

III.  CRYSTALLIZATION  HEXAGONAL. 
A.  LUSTRE  UNMETALLIC. 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

Ettringite  (p  373) 

1-75 

2 

Pyrosmalite  (p  318). 

3-32 

4-4-5 

Coquimbite  (p  373) 

2-2-1 

2-2-5 

Dreelite  (p  368)  R 

3-2-3-4 

3-5 

GMELINITE  (p.  323)  R*  . 
CHABAZITE  (p.  322)  R.. 
Levynite  (p.  321)  R  
TRIDYMITE  (p.  266)  
Hallite  (p  333).  .  .  . 

2-04-2-17 
2-08-2-19 
2-1-2-16 
2-28-233 
2-4 

4-5 

4-5 
4-4-5 

7 

MAGNESITE  (p.  380)  R.  . 
Cronstedtite  (p.  335)  
DIOPTASE  (p.  279)  R  

RlIODOCHROSITE  (p.  381) 

R 

3-3 
3-35 
3-35 

3-4-3-7- 

3-5^-5 
25 
5 

3-5-4-5 

Cancrinite  (p.  295)  

2-4-2-5 

5-6 

Volborthite  (p.  352)  

3-55 

3-3-5 

Chalcophyllite  (p.  352).  . 
NEPHELITE  (p.  294)  

2-4-2-66 
2-5-2-65 

2 
5-5-6 

BRUCITE  (p.  259)  R  

SlDERITE(p.  381)  R  

3-6-4 
3-7-3-9 

2-5 
3-5-4-5 

*  Species,  after  whose  names  an  R  is  written,  belong  to  the  Rhombohedral  Division. 


442 


APPENDIX. 


i  ». 

Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

QUARTZ  (p.  262)  R  

2-5-2-8 

7 

Wurtzite  (p    220") 

3-98 

3-5-4 

CALCITE  (p.  376)  R  
Microsommite  (p.  295)  .  . 
Alunite  (p.  374)  R  

2-5-2-78 
260 
2-6-2-75 

2-5-3-5 
6 
3  -5-4 

CORUNDUM  (p.  245)  R.  . 
WILLEMITE  (p.  279)  R.  . 
SMITHSONITE  (p.  382)  R 

3-9-4-16 
3-9-4-3 

4-4-45 

9 
5-5 
5 

BERYL  (p.  277) 

2-6-2-76 

7-5-8 

Parisite  (p   386) 

4-35 

4-5 

PENNINITE  (p.  333)  R 

2-6-2-85 

2-2-5 

Covellite  (p   227). 

4-6 

1-5-2 

?  BIOTITE  (p.  290)  

2-7-31 

2-5-3 

Cerite  (p.  318). 

4-91 

5-5 

Catapleiite  (p.  317).      . 

2-8 

6 

Fluocerite  (p  242) 

4'7 

4  5 

DOLOMITE  (p.  379)  R  
?  PROCHLORITE  (p.  335). 

2-8-2-9 
2-8-2-96 

3-5-4 

1-2 

GKEENOCKITE  (p.  220)  .  . 
ZINCITE  (p.  244)  

3-8-5 
5-4-5-7 

3-3-5 
4-4-5 

Eudialyte  (p.  277)  R 

2-9-3 

5-5 

lodyrite  (p  238) 

5-5-5-7 

soft 

TOURMALINE  (p.  307)  R. 
ANKERITE  (p.  380)  R.  .  . 
APATITE  (p.  342)  

2-94-3-3 
2-95-3-1 
2-9-3  25 

6-5-7-5 
3-5-4 
5 

PROUSTITE  (p.  231)  R.  .. 
PYRARGYRITE  (p.  230)  R. 

Schwartzembergite      (p. 

5-4-5-56 
5-7-5-9 

2-2-5 
2-2-5 

Phenacite  (p.  279)  R 

2-96-3 

8 

240) 

5  -7-6  -3 

2-2-5 

LEPIDOMELANE  (p.  291). 

Seybertite  (p.  336).  .    .  . 

3 
3-3-1 

3 
4-5 

Susannite  (p.  369)  R  
PYROMORPHITE  (p.  344) 

6-55 
6-5-7-1 

2-5 
3-5-4 

Friedelite  (p.  280)  R  
Breunerite  (p.  380)  R 

3-07 
3-3-2 

4-75 
4-4-5 

VANADINITE  (p.  345).  .  . 
MIMETITE  (p  344) 

6-7-7-23 

7-7-25  - 

2-5-3 
3-5 

B.  LUSTRE  METALLIC. 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

GRAPHITE  (p.  208)  
Chalcophanite  (p.  261).  . 
PYRRIIOTITE  (p.  219).  .  . 
MOLYBDENITE  (p.  211). 
MENACCANITE  (p  247)  R 

2-1-2-23 
3-91 
4-4-4-7 
4-4-4-5 
4-5-5 

1-2 
2-5 
3-5-4-5 
1-1-5 
5-6 

i  TELLURIUM  (p.  205)  
Allemontite  (p.  205)  
ANTIMONY  (p.  205)  R.  .  . 

iTETRADYMITE  (p.  211). 
!NlCCOLITE  (p  220). 

6-1-6-3 
6-13-6-2 
6-6-6-7 

7-2-7-9 

7-3-7-7 

2-2-5 
3-3-5 
3-3-5 
2 
5-5  -5 

HEMATITE  (p.  246)  R.  .  . 
Beyrichite  (p.  219) 

4-5-5-3 

4-7 

5-5-6-5 
3  3-5 

Breithauptite  (p.  221).  .  . 
Joseite  (p  211) 

7-54 
7'93 

5-5 

soft. 

MILLERITE  (p  219)  R 

4-6-5-65 

3-3-5 

Wehrlite  (p  211)  

8  '44 

1-2 

ZINCITE  (p.  244)  

5-4-5-7 

4-4-5 

CINNABAR  (p.  218)  R.  .  . 

9-0 

2-25 

PYR  \RGYRITE  (p  230)  R 

5-7-5-9 

2  2-5 

BISMUTH  (p  205) 

9-73 

2-2-5 

ARSENIC  (p.  204)  R  

5-93 

3-5 

IRIDOSMINE  (p.  202)  .... 

19-3-21 

6-7 

IV.   CRYSTALLIZATION   ORTHO-RHOMBIC. 
A.  LUSTRE  UNMETALLIC. 

i 

jSpec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

Struvite  (p.  349) 

1-65-1-7 

1-73 
1-73 
1-75 
1-89 
1-94 

2-04 
2-07 
2-09-2-2 
2-20 
2-17-2-25 
2-26 
2-265 
2-27 
2-25-2-36 
2-3-2-4 
2-34 

2 

2-2-5 
3-3-5 
2-2-5 
2-2-5 
2-2-5 
2 

2-2-5 
1-5-2-5 
3-5-4 
4-4-5 
5-55 

4-5 
5-5 
4-4-5 
5-5-5 
3-4 

SCORODITE  (p.  353)  
Forsterite  (p.  278) 

3-1-3-3 
32-3-33 
3-1-3-38 
3-2-3-4 
316-3-9 
3-32 
3-39 
3-39 
3-3-3-5 
3-3-3-5 
3-45 
3-48 
3-49 
3-5 
3-54-3-6 
3-4-3-68 
3-62 
3-4-3-8 
3-4-3-8 

3-5-4 
6-7 
6-6-5 
3-5-4 
4-5-5 
3 
5-6 
3-5^ 
6-5-7 
6-7 
2-3 
1-5-2 
6 
2-5-3 
5 
8 
6-7 
4-5-5 
7-7-5 

Lecontite  (p   370) 

Aphthitalite  (p.  368)  
Mascagnite  (p.  370)  
EPSOMITE  (p.  372)  
Fauserite  ^p.  372)  
Nitre  (p   357) 

ZOISITE  (p  286)  

Duf  renite  (p.  356)  
CALAMINE  (p.  317)  
?  Astrophyllite  (p.  291).  . 
HYPERSTHENE  (p.  268). 
Euchroite  (p.  351)  

Erythrosiderite  (p.  239)  . 
Goslarite  (p.  373)  
SULPHUR  (p.  206)  
STILBITE  (p.  324)  

DIASPORE  (p.  257)  
CHRYSOLITE  (p.  278)  
Uranospinite  (p.  357).  .  . 
ORPIMENT  (p.  209)  

PlIILLIPSTTE  (p.   323)  .  .  . 

NATROLITE  (p.  320)  

Pilinite  (p  322) 

Langite  (p  375)  

Gismondite  (p.  319)  
Eudnophite  (p.  322)  
Epistilbite  (p.  325)  
TUOMSONITE  (p.  320).  .  . 
WAVELLITE  (p.  354).  .  .  . 

TRIPHYLITE  (p.  347).  .  . 
TOPAZ  (p  310) 

Ardennite  (p.  288)  .... 

TRIPLITE  (p  347)  

STAUROLITE  (p.  314).  .  . 

DETERMINATION    OF    MINERALS. 


443 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

Foresite  (p.  325)  
KAOLINITE  (p  329) 

241 
2-4-2-63 

1-2-5 

CHRYSOBKRYL  (p.  252).  . 
Asmanite  (p.  266). 

3-5-3-84 
3-62 

8-5 
5-5 

Peo-anite  (p   356)  

2-5 

3-35 

STRONTIANITE  (p.  384) 

3-6-3-71 

3-5-4 

Kieserite  (p  372) 

2-52 

2-5 

Knebelite  (p.  278) 

3-71 

6-5 

IOLITE  (p  289)  

2-56-2-67 

7-7-5 

LlBETIIENITE  (p.  351)  .  . 

3-6-3-8 

4 

LANTHANITE  (p.  388) 

2-6-2-67 

2-5-3 

Bromlite  (p   384)  

3-7 

4-4-5 

TALC  (p.  326)  
Aspidolite  (p.  290)  

2-6-2-8 

2-72 

1-1-5 
1-2 

ATACAMITE  (p.  239)  
Claudetite  (p.  262)  

3-76-3-9 
3-85 

3-3-5 

PYROPIIYLLITE  (p.  327). 

PlILOGOPITE  (p    290) 

2-75-2-9 

2-78-2-85 

1-2 
2-5-3 

Hortonolite  (p.  278)  
CELESTITE  (p  366) 

3-91 
3-9-3-98 

•  6-5 
3-3-5 

Haidiiigerite  (p.  349)  
PREUNITE  (p.  318)  

2-85 
2-8-2-9 

1  -5-2-5 
6-6-5 

Roepperite  (p.  278)  
Sternbergite  (p.  218)  

3-98-4-08 
4-21 

5-5-6 
1-1-5 

LEPIDOLITE  (p.  292).  .  .  . 
Cryophyllite  (p   293) 

2-84-3 
2  91 

2-5-4 
2-25 

Cervantite  (p.  262)  
iTephroite  (p   278) 

4-08 
4-4-12 

4-5 
5'5  6 

ARAGONITE  (p.  383).  .  .  . 
ANHYDRITE  (p  367) 

2-93 

2-9-2-98 

3-5-4 
3  3-5 

?BROOKITE  (p.  255).  .  .  . 

GrOTIllTE  (p    258). 

4-03-4-23 
4-4-4 

5-5-6 
5-5-5 

Leucophanite  (p.  278)  .  .  . 
Herderite  (p  348) 

2-97 

2-98 

3-5-4 
5 

OLIVENITE  (p.  351)  

WlTIIERITE  (p.  384)    . 

4-1-4-4 
4-3 

3 

3-3-75 

Villarsite  (p   318) 

2-99 

4-5 

BARITE  (p  365) 

4-3-4-7 

25-3*5 

?MARGARITE  (p.  335).. 

Fluellite  (p   242)  

2-99 

3-5-4-5 
3 

Molybdite(p.  262)  
EUXENITE  (p.  340)  

4-5 

4-6-5 

1-2 
6-5 

Manganocalcite  (p.  384)  . 
Diaclasite  (p   269) 

3-04 
3-05 

4-5 
3-5-4 

Polyimgnite  (p.  340)  
i  Poly  erase  (p   340)   .  .  . 

4-7-4-85 
5-1 

6-5 
5-5 

Kupfferite  (p  274)  

3-08 

5-5 

^ESCIIYNITE  (p.  340)  .... 

4-9-5-14 

5-6 

Seybertite  (p   336) 

3-3  -1 

4-5 

Cotmmite  (p.  239)      .... 

5  24 

soft 

Tyrolite  (p   352)  

3-3-1 

1-2 

VALENTINITE  (p.  262)  . 

5-57 

2-5-3 

AUT  UNITE  (p  357) 

3-05  3*19 

2-2-5 

Descloizite  (p   345) 

5-84 

3-5 

ANTHOPHYLLITE  (p  273) 

3-1-3-2 

5-5 

Pucherite  (p.  345)    

5-91 

4 

ANDALUSITE  (p.  309)  .  .  . 
HUMITE  (p  305) 

3-1-3-2 
3-1-3-24 

7-5 
6-6-5 

IANGLESITE  (p.  367)  
LEADHILLITE  (p  368) 

6-1-6-39 
6  -26-6  -44 

2-75-3 
2-5 

Monticellite  (p  278,  

3-3-25 

5-5-5 

CERUSSITE  (p.  385)  

6-48 

3-3-5 

ClIILDRENITE  (p    355) 

3-18  3  '24 

4-5  5 

Nadorite  (p   348) 

7-02 

3 

ENSTATITE  (p  268) 

3-1-33 

5-5 

'Mendipite  ({>.  240)     

7-7-1 

2-5-3 

B.  LUSTRE  METALLIC. 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

Hardness. 

ILVAITE  (p.  287)  

MANGANITE  (p.  258)  
Chalcostibite  (p.  228)... 
ENARGITE  (p.  235)  
Epigenite  (p.  236)  

3-7-4-2 
4-2-44 
4-25-5 
4-44 

5-5-6 
4 
3-4 
3 
3-5 

JAMESONITE  (p.  229).  .  .  . 
CHALCOCITE  (p.  217)... 
COLUMBITE  (p.  338)  

BOURNONITE  (p.  231)  .  .  . 

Diaphorite  (p  230) 

5-5-5-8 
5-5-5-8 
5-4-6-5 
5-7-5-9 
5-90 

2-^ 
25-3 
6 
2-5-3 
2-5-3 

Spathiopyrite  (p.  224)  .  . 

4-5 

6-7 

Glaucodot  (p  226) 

6-0 

5 

STIBNITE  (p.  210)  

4-52 

2 

Aikinite  (p.  232)  

6-1-6-8 

2-25 

Famatinite  (p.  236)  
Klaprotholite  (p.  229).  .  . 
MARCASITE  (p.  225)  
Livingstonite  (p.  210).  .  . 
Stylotypite  (p  232} 

4-57 
4-6 

4-7-4-85 
4-81 
4-79 

3-5 
2-5 
6-6-5 

2 
3 

POLYBASITE  (p.  235)  

STEPHANITE  (p.  234).  .  . 
Stromeyerite  (p.  218).  .  . 
Wolfachite  (p.  225)  
Arsenopyrite  (p.  225) 

6-21 
6-27 
6-2-6-3 
6-37 
6-64 

2-3 
2-2-5 
2-5-3 
5-5 
5-5-6 

PYROLUSITE  (p.  256)  .  . 

4-82 

2-2-5 

Jordanite  (p  229)  

6-4 

Wittichenite  (p.  232)  
G-uanajuatite  (p.  211).  .  . 
Emplectite  (p.  228)  
ZlNKENITE  (p.  228)  

SARTORITE  (p.  228)  

5 
5-15 
5-1-5-26 
535 
5-39 

3-5 

2-2-5 

3-3-5 
3 

Geocronite  (p.  235)  
Alloclasite  (p.  226)  
'BISMUTHINITE  (p.  210). 
Leu  copy  rite  (p.  226).  .  .  . 
iLollingite  (p.  226)  .  '.  

6-4-6-6 
6-6 
6-4-7-2 
6-2-7-3 

6-8-8-7 

2^3 
45 
2 
5^5-5 

SAMARSKITE  (p.  339)  .  .  . 

DUFRENOYSITE  (p.  229). 

YTTROTANTALITE       (p. 
339). 

5-45-5-7 
5-5-5-6 

5-4-5-9 

5-5-6 
3 

5-5-5 

ACANTHITE  (p.  217)  .  .  . 

TANTALITE  (p,  337)  
HESSITE  (p.  216).  
DYSCR  \SITE  (p  212) 

7-16-7-3 
7-8 
8-3-8-6 
9-4-9-8 

2-5 
6-6-5 
2-3-5 
3-5-4 

444 


APPENDIX. 


CRYSTALLIZATION  MONOCLINIC. 


A.  LUSTRE  UNMETALLIC. 


Spec.  Gravity 

Hardness. 

| 

Spec.  Gravity 

Hardness. 

Natron  (p  386). 

1-42 

1-1-5 

SPODUMENE  (p  273) 

3-1-3-19 

6-5-7 

MlKABILITE  (p.  370)..  . 

1-48 

1-5-2 

LAZULITE  (p.  353)..    . 

3-3-12 

5-6 

BORAX  (p  359) 

1-72 

2-25 

EUCLASE  (p  311) 

3-1 

7-5 

Copperas  (p.  372)  

1-8-2-2 

2-2-5 

Johannite  (p   375) 

319 

2-2-5 

GAY-LUSSITE  (p.  387).  .  . 
Botrvogen  (p.  373) 

1-9-1-99 
2-04 

2-3 

2-25 

ClIONDRODITE    (p.    305). 
ICLINOIIUMITE  (p.  306) 

3-1-3-24 
3-1-3-24 

6-6-5 
6-6-5 

Whewellite  (p.  390)   

2-5-3 

FlBROLTTE  (p.  309)     .  .  . 

3-2-3-3 

6-7 

TRONA  (p.  386)  

211 

2-5-3 

ALLANITE  (p.  286)  

3-4-2 

5-5-6 

Hydromagnesite  (p.  387) 

2-14-2-18 

35 

EPIDOTE  (p  285)       .... 

3-25-3-5 

6-7 

SCOLECITE  (p.  321)  

HEULANDITE  (p  325) 

2-1-2-4 

2-2 

5-5-5 
3-5-4 

PYROXENE  (p.  270;  
Acmite  (p   272) 

3-2-3-5 
3-2-3-53 

5-6 
6 

GYPSUM  (p.  370)       ... 

2-3-2-33 

1-5-2 

Piedmont!  te  (p.  286)     . 

3-404 

6-5 

GIBBSITE  (p.  260)  

23-2-4 

2-5-3-5 

jREALGAR  (p.   209). 

3-4-36 

1-5-2 

Syngenite  (p.  372) 

2-25-2-6 

2-5 

TlTANITE  (p    313)  .  . 

3-4-3-56 

5-5-5 

LAUMONTITE  (p.  310). 

225-2-36 

35-4 

^Egirite  (p.  272)  

3-45-3-6 

5-5-6 

Brewsterite  (p.  325)  
Petahte  (p.  273)  . 

2-43 
2-4-2-5 

4-5-5 
6-6'5 

Keilhauite  (p.  314)  
AZURITE  (p  389)  .    . 

3-7 
3-5-3-83 

6-5 
3-5-4 

HARMOTOME  (p.  324)  .  .  . 
ORTHOCLASE  (p.  303).  .  . 
VIVIANITE  (p.  349)  
RIPIDOLITE  (p.  334)  
PECTOLITE  (p.  315) 

2-45 
2-4-26 

2-58-2-68 
2-6-2-8 
2-65-2-8 

4-5 
6-6-5 
1  5-2 
2-2-5 
5 

BARYTOCALCITE  (p.  386; 
MALACHITE  (p.  389)  
BROCHANTITE  (p.  374).  . 
Trogerite  (p.  357)  
Durangite  (p   348) 

3-64-3  66 
3-7-4-01 
3-8-3-9 
3-96 
3-95-4-03 

4 
3-5^ 
3-5-4 

5 

PHARMACOLITE  (p  348) 

2-6-2-73 

2-2-5 

Gadolinite  (p.  287)  

4-4-5 

6-5-7 

GLAUBERITE  (p.  369)  .  .  . 
?  MUSCOVITE  (p.  291).  .  . 
Vaalite  (p.  333)  

WOLLASTONITE  (p    269) 

2-6-2-85 
2-7-3-1 

2-78-2-9 

2-5-3 
2-2-5 

4-5^5 

Pyrostilpnite  (p.  230)  .  .  . 
CLINOCLASITE  (p.  352)  .  . 
MONAZITE  (p.  346),  Tur- 
nerite  . 

4-2-4-25 
4-2-4-36 

4-9-5-26 

2 
2-5-3 

5-5-5 

DATOLITE  (p.  312) 

2-8-3 

5-5-5 

MlARGYRITE  (p.  227)  .  . 

5-2-5-24 

2-2-5 

HYALOPHANE  (p.  300) 

2-8-2-9 

6-6-5 

LlNARITE  (p.  374)  

5-3-5-45 

2-5 

Corundophilite  (p.  336). 
Isoclasite  (p.  351)  
PACHNOLITE  (p.  243)  .  .  . 
?MARGAKITE  (p.  335).  .  . 
AMPIIIBOLE  (p  274) 

2-9 
2-92 
2-93-3 
2-99 
2*9-3-4 

2-5 

1-5 
2-5-4 
3-5-4-5 
5  6 

VAUQUELINITE  (p.  364). 
Laxmannite  (p.  364).  .  .  . 
Walpurgite  (p.  357)  
CROCOITE  (p.  363)  
Lanarkite  (p   369) 

5-5-5-78 
5-77 
5-8 
5-9-6-1 
6-3-7 

2-5-8 
3 

2-5-3 
2-25 

ERYTHRITE  (p  350) 

2*95 

2-2-5 

Caledonite  (p  369) 

6-4 

25-3 

WAGNERITE  (p.  346).  .  .  . 
Kottigite  (p.  350)  
Ludlamite  (p  350). 

3-07 
3-1 
3-12 

5-5-5 
2-5-3 
3-5 

Megabasite  (p.  361)  
Hiibnerite  (p.  361)  
WOLFRAMITE  (p.  361).   . 

6-45 

7-14 
7-1-7-55 

3-5-4 
4-5 
5-5-5 

B.  LUSTRE  METALLIC. 


Spec.  Gravity 

Hardness. 

Spec.  Gravity 

5-4 
6-34 
6-64 
7-1-7-55 

8-8-3 

Hardness. 

2-5 
2-5 
2-2-5 
5-5-5 
1-5-2 

ALLANITE  (p  286) 

3-4-2 
4-46 
4-9-51 
4-12^-23 
5-2-5-4 

5-5-6 
3-5 
4-5 
5-5-6 
2-25 

Plagionite  (p.  229)  

Clarite  (p.  236) 

Meneghinite  (p.  234)  
FREIESLEBENITE  (p.230) 
WOLFRAMITE  (p.  361)  .  . 
SYLVANITE  (p.  226)... 

Crednerite  (p.  256)     . 

?  BROOKITE  (p.  255)  

MlARGYRITE  (p.   227)  .  .  . 

DETERMINATION    OF    MINERALS. 


445 


CRYSTALLIZATION  TRICLINIC. 


Spec.  Gravity 

Hardness. 

S^ec.  Gravity 
3-3-11 

3-27 
3-3-3-37 
3-4-3-7 
8-4-3-7 
3-5 
3-5-3-58 
3-8-3-9 
4-4-4 

Hardness. 

6 

6-5-7 
5-5-6 
5-7-25 
5-5-6-5 
4 
3-5 
3-5-4 
4-5-5 

SA.SSOLITK  (p.  358) 

1-48 
2-21 
2-48 
254 
2-59-2-65 
265-2-69 
2-67-2-76 
2-61-274 
2-66-2-78 
2-96 
2-9-3 

1 
2-5 
2-2-5 

6-7 
6-7 
6 
6 
6-7 
7 
2-5 

AMBLYGONITE  (p.  347).  . 
•Hebronite  (p.  348)  

CHALCANTHITE  (p.  372). 
Wapplerite  (p  349) 

AXINITE  (p  288) 

Microcline  (p  304). 

Babingtonite  (p.  273)... 
CYANITE  (p.  310)  
RHODONITE  (p.  272)  
Veszelyite  (p  351) 

ALBITE  (p.  301)  
OLIGOCLASE  (p.  301).  ... 
LABRADORITE  (p.  299)  .  . 
ANDKSITE  (p.  300)   
ANORTHITE  (p.  299)  
Danburite  (p   289) 

Roselite  (p.  350)  

?  BROCHANTITE  (p.  374). 
Pseudomalachite  (p.  352) 

CRYOLITE  (p.  242)  

HE.  AUXILIARY  TABLES. 


A.    Minerals  whose  Hardness  is  equal  to,  or  greater  than,  7  (  Quartz=7). 


Quartz  (p.  262) 
Tridymite  (p.  266) 
Danburite  (p.  289) 
Boracite  (crystals)  (p.  359) 
Cyanite  (p.  310) 
Tourmaline  (p.  307) 
G-arnet  (p.  280) 
lolite  (p.  289) 
Staurolite  (p.  314) 
Schorlomite  (p.  315) 


Hardness. 
7 
7 
7 
7 
5 --7 -25 


Cryst.* 
III.  (R) 
III. 
VI. 
I. 
VI. 


6-5-7-5   III.  (R) 
6-5-7-5        I. 

7-7-5        IV. 

7-7-5 

7-7-5 


IV. 


Euclase  (p.  311) 
Zircon  (p.  282) 
Andalusite  (p.  309) 
Beryl  (p.  277) 
Phenacite  (p.  279) 
Spinel  (p.  249) 
Topaz  (p.  310) 
Chrysoberyl  (p.  252) 
Corundum  (p.  245) 
Diamond  (p.  206) 


Hardness. 

Cryst. 

7-5 

V. 

7-5 

II. 

7-5 

IV. 

7-5-8 

III. 

7-5-8 

III.  (R) 

8 

I. 

8 

IV. 

8-5 

IV. 

9 

III.  (R) 

10 

I. 

The  following  minerals  have  hardness  equal  to  6-7,  or  6 '5-7  : 

Iridosmine,  III. — Cassiterite,   II.;    Diaspore,   IV.;    Chrysolite,  IV.;    Spodumene,  V.; 
Epidote,  V.;  Ardennite,  IV.;  Gadolinite,  V.;  Fibrolite,  V.;    Feldspars,  VI;  Axinite,  VI. 

B.  Unmetallic  Minerals  which  are  distinctly  FOLIATED  in  some  of  their  varieties. 

1.  Micaceous  :  easily  separable  into  very  thin  lamina?,  flexible  to  slightly -brittle. 

a.  MICAS  (pp.  289  to  293) :  laminas  tough  and  elastic,  except  when  they  have  under- 
gone alteration  ;  anhydrous.     Here  are  included  the  species  :    Phlogopite  ;    Biotite  ;    Musco- 
vite ;    Lepidolite  ;  Cryophyllite.     These  graduate  into  the 

HYDRO-MICAS  (pp.  331,  332),  in  which  the  laminae  are  inelastic  and  more  or  less 
brittle.  Here  belong  :  Fahlunite  ;  Margarodite  ;  Damourite  ;  Paragonite  ;  Cookeite  ;  Eu- 
phyllite  ;  Oellacherite,  etc.;  and  related  to  ^.hese,  Margarite. 

Lepidomelane  and  Astrophyllite  are  other  micas  (anhydrous  or  nearly  so)  whose 
folia  are  nearly  inelastic. 

b.  CIILORITES  (pp.  333  to  335) :    laminae  tough  but  mostly  inelastic  ;  hydrous  ;  color 
generally  dark-green.     Here  are  included  :   Penninite  ;  Ripidolite  ;  Prochlorite,  etc.     These 
are  related  to  the  VERMICULJTES  (p.  33-3),  in  which  the  laminae  are  less  tough,  being  more  or 
less  brittle  :  Jefferisite  ;  Pyrosclerite,  etc. 

c.  Pyrophyllite,    Talc,    sometimes   rather   micaceous,    laminae    soft,    and    somewhat 
greasy  to  the  feel.     Brucite  is  related  in  character,  but  differs  chemically  in  being  soluble 
in  acids. 

d.  Torbermte,  color  deep-green ;  Autunite,  color  yellow  to  bright-green,  laminae  brittle. 


*  Here,  as  elsewhere,  I.  =  Isometric;  II.  =  Tetragonal ;  III.  =  Hexagonal  ;  IV.  =0rthorhom- 
bic  ;  V.  =Monoclinic  ;  VI.  Triclinic. 


446  APPENDIX. 

2.  Not  properly  micaceous,  though  separable  more  or  less  easily  into  thin  laminae. 

Chloritoid   (p.  336)   and  Seybertite  (p.  336)  are  foliated,  the  laminae  not  separating 
easily.     So  also  Bronzite,  Hypersthene,  Diallage,  and  Marmolite. 

Gypsum  sometimes  occurs  in  soft,  separable  laminae  (var.  Selenite),  slightly  flexible. 
Zincite  and  Erythrite  are  sometimes  foliated  but  not  separable. 

C.    UnmetaMc  Minerals  which  in  some  of  their  varieties  have  a  FIBROUS  structure. 

1.  Easily  separable  into  flexible  fibres. 

Asbestus  (=ampbibole) ;  Crocidolite  ;   Chrysotile  (— serpentine);  Anthrosiderite. 

2.  Fibrous,  not  easily  separable ;   structure  graduating  into  columnar. 

Anhydrous  Silicates :— Enstatite  ;  Wollastonite  ;  Fibrolite  ;  also,  though  more  properly 
columnar  in  structure  : — Cyanite  ;  Epidote  ;  Tourmaline. 

Hydrous  Silicates,  Zeolites  mostly  : — Thomsonite  ;  Okenite  ;  Natrolite  ;  Scolecite  ;  Pecto- 
lite  ;  Carpholite.  Also  some  Serpentine. 

Phosphates  ;  Arsenates  : — Wavellite  ;  Cacoxenite  ;  Pharmacolite  ;  Dufrenite  ;  Olivenite ; 
Vivianite ;  Pyromorphite. 

Sulphates:  Anhydrite;  Barite ;  Celestite;  Gypsum. 

Carbonates: — Calcite;  Diallogite  ;    Magnesite  ;  Hydromagnesite ;  Aragonite  ;  Malachite. 

Also  : — Brucite  (nemalite)  ;  Sussexite ;  Ulexite. 


APPENDIX  D. 


CATALOGUE   OF   AMERICAN   LOCALITIES  OF   MINERALS. 


The  following  catalogue*  may  aid  the  mineralogical  tourist  in  selecting  his  routes  and 
arranging  the  plan  of  his  journeys.  Only  important  localities,  affording  cabinet  specimens, 
are  in  general  included  ;  and  the  names  of  those  minerals  which  ore  obtainable  in  good  speci- 
mens are  distinguished  by  italics.  When  a  name  is  not  italicized  the  mineral  occurs  only  spar- 
ingly or  of  poor  quality.  When  the  specimens  to  be  procured  are  remarkably  good,  an  excla- 
mation mark  (!)  is  added,  or  two  of  these  marks  (!  !)  when  the  specimens  are  quite  unique. 

MAINE. 

ALBANY.  — Beryl !  green  and  black  tourmaline,  feldspar,  rose  quartz,  rutile. 

AROOSTOOK. — Red  hematite. 

AUBURN. — Lepidolite,  amblygonite  (hebronite),  green  tourmaline. 

BATH.— Vesuvianite,  garnet,  magnetite,  graphite. 

BETHEL.  —  Cinnamon  garnet,  calcite,  sphene,  beryl,  pyroxene,  hornblende,  epidote, 
graphite,  talc,  pyrite,  arsenopyrite,  magnetite,  wad. 

BINGHAM. — Massive  pyrite,  galenite,  blende,  andalusite. 

BLUE  HILL  BAY. — Arsenical  iron,  molybdenite!  galenite,  apatite!  fluorite  !  black  tourma- 
line (Long  Cove),  black  oxide  of  manganese  (Osgood's  farm),  rhodonite,  bog  manganese, 
wolframite . 

BOWDOIN. — Rose  quartz. 

Bo WDOINII AM.  — Beryl,  molybdenite. 

BRUNSWICK. — Green  mica,  garnet/  black  tourmaline/  molybdenite,  epidote,  calcite,  mus- 
covite,  feldspar,  beryl. 

BUCKFIELD. — Garnet  (estates  of  Waterman  and  Lowe),  iron  ore,  muscomte  !  tourmaline! 
magnetite. 

CAMDAGE  FARM.  — (Near  the  tide  mills),  molybdenite,  wolframite 

CAMDEN. — Made,  galenite,  epidote,  black  tourmaline,  pyrite,  talc,  magnetite. 

CARMEL  (Penobscot  Co.).  —  Stibnite,  pyrite,  macle. 

CORINNA.  — Pyrite,  arsenopyrite. 

DEER  ISLE. — Serpentine,  nerd-antique,  asbestus,  diallage,  magnetite. 

DEXTER. — Galenite,  pyrite,  blende,  chalcopyrite,  green  talc. 

DIXFIELD. — Native  copperas,  graphite. 

EAST  WOODSTOCK. — Muscovite. 

FARMINGTON. — (Norton's  ledge),  pyrite,  graphite,  bog  ore,  garnet,  staurolite. 

FREEPORT. — Rose  quartz,  garnet,  feldspar,  scapolite,  graphite,  muscovite. 

FRYEBURG. — Garnet,  beryl. 

GEORGETOWN. — (Parker's  island),  beryl!  black  tourmaline. 

GREENWOOD. — Graphite,  black  manganese,  beryl!  arsenopyrite,  cassiterite,  mica,  rose 
quartz,  garnet,  corundum,  albite,  zircon,  molybdenite,  magnetite,  copperas. 

*  The  catalogue  is  essentially  the  same  as  that  published  in  the  5th  Edition  of  Dana's  Sys- 
tem of  Mineralogy,  1868.  The  names  of  a  considerable  number  of  new  localities  havetbeen 
added,  however,  which  have  been  derived  from  various  printed  sources,  and  also  from  private 
contributions  from  Prof.  G.  J.  Brush,  Mr.  G.  W.  Hawes,  Mr.  J.  Willcox,  and  others. 


44:8  APPENDIX. 

HEBRON.  —  Cassitente,  arsenopyrite,  idocrase,  lepidolite,  amblygonite  (Jiebronite),  rubeUitef 
indicolite,  green  tourmaline,  mica,  beryl,  apatite,  albite,  childrenite,  cookdte. 

JEWELL'S  ISLAND. — Pyrite. 

KATAHDIN  IKON  WORKS. — Bog-iron  ore,  pyrite,  magnetite,  quartz. 

LETTER  E,  Oxford  Co. — Stalirolite,  made,  copperas. 

LlNN^us. — Hematite,  limonite,  pyrite,  bog-iron  ore. 

LITCHFIELD. — Sodalite,  cancrinite,  elceolite,  zircon,  spodumene,  muscovite,  pyrrhotite. 

LUBEC  LEAD  MINES.  —  Oalenite,  chalcopyrite,  blende. 

MAOHIASPORT.  —  Jasper,  epidote,  laumontite. 

MADAWASKA  SETTLEMENTS. —  Vivianite. 

MTNOT.  — Beryl  smoky  quartz. 

MONMOUTH. — Actinolite,  apatite,  elceolite,  zircon,  staurolite,  plumose  mica,  beryl,  rutile. 

MT.  ABRAHAM. — Andalusite,  staurolite. 

NORWAY.  —  Chrysoberyl!  molybdenite,  beryl,  rose  quartz,  orthoclase,  cinnamon  garnet. 

ORR'S  ISLAND. — Steatite,  garnet  andalusite. 

OXFORD.  —  Garnet,  beryl,  apatite,  wad,  zircon,  muscovite,  orthoclase. 

PARIS. — Green!  red!  black,  and  blue  tourmaline!  mica!  lepidolite!  feldspar,  albite,  quartz 
crystals  !  rose  quartz,  cassiterite,  amblygonite,  zircon,  brookite,  beryl,  smoky  quartz,  spodu- 
mene, cookdte,  leucopyrite. 

PARSONSFIELD. —  Vesutianite  !  yellow  garnet,  pargasite.  adularia,  scapolite,  galenite,  blende, 
chalcopyrite. 

PERU —  Crystallized  pyrite. 

PHIPPSBURG. —  Yellow  garnet !  manganesian  garnet,  vesuvianite,  pargasite,  axinite,  laumon- 
tite !  chabazite,  an  ore  of  cerium  ? 

POLAND.  — Vesuvianite,  smoky  quartz,  cinnamon  garnet. 

PORTLAND. — Prehnite,  actinolite,  garnet,  epidote,  amethyst,  calcite. 

POWNAL. — Black.tourmaline,  feldspar,  scapolite,  pyrite,  actinolite,  apatite,  rose  quartz. 

RAYMOND. — Magnetite,  scapolite,  pyroxene,  lepidolite,  tremolite,  hornblende,  epidote,  ortho- 
clase, yellow  garnet,  pyrite,  vesuvianite. 

ROCKLAND.  —  Hematite,  tremolite,  quartz,  wad,  talc. 

RUMFORD. —  Yellow  garnet,  vesmianite,  pyroxene,  apatite,  scapolite,  graphite. 

RUTLAND. — Allanite. 

SANDY  RIVER. — Auriferous  sand. 

SANFORD,  York  Co. —  Vesuvianite  !  albite,  calcite,  molybdenite,  epidote,  black  tourmaline, 
labradorite. 

SEAUSMONT.- — Andalusite,  tourmaline. 

SOUTH  BERWICK. —Made. 

STANDISII.  —  Columbite  ! 

STREAKED  MOUNTAIN. — Beryl!  black  tourmaline,  mica,  garnet. 

THOMASTON.  —  Calcite,  tremolite,  hornblende,  sphene,  arsenical  iron  (Owl's  head),  black 
manganese  (Dodge's  mountain),  thomsonite,  talc,  blende,  pyrite,  galenite. 

TOPSHAM.  —  Quartz,  galenite,  blende,  tungstite  ?  beryl,  apatite,  molybdenite,  columbite. 

UNION. — Magnetite,  bog-iron  ore. 

WALES. — Axinite  in  boulder,  alum,  copperas. 

WATERVILLE —  Crystallized  pyrite. 

WINDHAM  (near  the  bridge). — Siaurolite,  spodumene,  garnet,  beryl,  amethyst,  cyanite, 
tourmaline. 

WINSLO  w.  — Cassiterite. 

WINTIIROP. — Staurolite,  pyrite,  hornblende,  garnet,  copperas. 

WOODSTOCK. — Graphite,  hematite,  prehnite,  epidote,  calcite. 

YORK. — Beryl,  vivianite,,  oxide  of  manganese. 

NEW  HAMPSHIRE. 

Ac  WORTH. — Beryl!  !  mica!  tourmaline,  feldspar,  albite,  rose  quartz,  columbite!  cyanite, 
autunite. 

ALSTEAD. — Mica!  !  albite,  black  tourmaline,  molybdenite,  andalusite,  staurolite. 

AMHERST. —  Vesuvianite,  yellow  garnet,  pargasite,  calcite,  amethyst,  magnetite. 

BARTLETT. — Magnetite,  hematite,  brown  iron  ore  in  large  veins  near  Jackson  (on  "  Bald 
face  mountain  "),  quartz  crystals,  smoky  quartz. 

BATH.  — Galenite,  chalcopyrite. 

BEDFORD. — Tremolite,  epidote,  graphite,  mica,  tourmaline,  alum,  quartz. 

BELLOWS  FALLS. — Cyanite,  staurolite,  wavellite. 

BRISTOL.— Graphite. 


AMERICAN   LOCALITIES.  449 

C  AMPTON.  — Beryl ! 

CANAAN. — Gold 'in  pyrites,  garnet. 

CHARLESTON. — Staurolite  made,  andalusite  made,  bog-iron  ore,  prehnite,  cyanite. 

CORNISH. — Stibnite,  tetrahedrite,  rutile  in  quartz!  (rare),  staurolite. 

CROYDEN. — lolite!  chalcopyrite,  pyrite,  pyrrhotite,  blende. 

ENFIELD. — Gold,  galenite,  staurolite,  green  quartz. 

FRANCESTON. — Soapstoae,  arsenopyrite,  quartz  crystals. 

FRANCONIA. — Hornblende,  staurolite!  epidote!  zoisite,  hematite,  magnetite,  black  and  red 
manganexian  gnrnets,  arsenopyrite  (danaite],  chalcopyrite,  molybdenite,  prehnite,  green 
quartz,  malachite,  azurite. 

GILFORD  (Gunstock  Mt.). — Magnetic  iron  ore,  native  "loadstone." 

GOSHEN.  —  Graphite,  black  tourmaline. 

GILMANTOWN.— Tremolite,  epidote,  muscovite,  tourmaline,  limonite,  red  and  yellow 
quartz  crystals. 

GRAFTON. — Mica!  (extensively  quarried  at  Glass  Hill,  2  m.  S.  of  Orange  Summit),  albite! 
blue,  green,  and  yellow  beryls  !  (\  m.  S.  of  0.  Summit),  tourmaline,  garnets,  triphylite,  apa- 
tite, fluorite. 

GRANTHAM.—  Gray  staurolite! 

GROTON. — Arsenopyrite,  blue  beryl,  muscovite  crystals. 

HANOVER. — Garnet,  a  boulder  of  quartz  containing  rutile  !  black  tourmaline,  quartz,  cya- 
nite, labradorite,  epidote. 

HAVERIIILL. — Garnet!  arsenopyrite,  native  arsenic,  galenite,  blende,  pyrite,  chalcopy- 
rite, magnetite,  marcasite,  steatite. 

HiLLSBORO1  (Campbell's  mountain). — Graphite. 

HINSDALE. — Rhodonite,  black  oxide  of  manganese,  molybdenite,  indicolite,  black  tour- 
maline. 

JACKSON.— Drusy  quartz,  tin  ore,  arsenopyrite,  native  arsenic,  fluorite,  apatite,  magnetite, 
molybdenite,  wolframite,  chalcopyrite,  arsenate  of  iron. 

JAFFREY  (Monadnock  Mb.).  —  Cyanite,  limonite. . 

KEENE. — Graphite,  soapstone,  milky  quartz,  rose  quartz. 

LANDAFF. — Molybdenite,  lead  and  iron  ores. 

LEBANON. — Bog-iron  ore,  arsenopyrite,  galenite,  magnetite,  pyrite. 

LISBON. — Staurolite,  black  and  red  garnets,  granular  magnetite,  hornblende,  epidote,  zoisite, 
hematite,  arsenopyrite,  galenite,  gold,  ankerite. 

LITTLETON. — Ankerite,  gold,  bornite,  chalcopyrite,  malachite,  menaccanite,  chlorite. 

LYMAN. — Gold,  arsenopyrite,  ankerite,  dolomite,  galenite,  pyrite,  copper,  pyrrhotite. 

LYME. —  Cyanite  (N.  W.  part),  black  tourmaline,  rutile,  pyrite,  chalcopyrite  (E.  of  E.  vil- 
lage), stibnite,  molybdenite,  cassiterite. 

MADISON. — Galenite,  blende,  chalcopyrite,  limonite. 

MERRTMACK. — Rutile/  (in  gneiss  nodules  in  granite  vein). 

MlDDLETOWN.  — Rutile. 

MONADNOCK  MOUNTAIN. — Andalusite,  hornblende,  garnet,  graphite,  tourmaline,  ortho- 
clase. 

MOOSILAUKE  MT. — Tourmaline. 

Mo ULTONBO ROUGH  (Red  Il\\\}.—Hornbende,  bog  ore,  pyrite,  tourmaline. 

NEWINGTON. — Garnet,  tourmaline. 

NEW  LONDON. — Beryl,  molybdenite,  muscovite  crystals. 

NEWPORT. — Molybdenite. 

ORANGE.  —Blue  beryl* !  Orange  Summit,  chrysoberyl,  mica  (W.  side  of  mountain),  apatite, 
galenite,  limonite. 

ORFORD.  —  Brown  tourmaline  (now  obtained  with  difficulty),  steatite,  rutile,  cyanite,  brown 
iron  ore,  native  copper,  malachite,  galenite,  garnet,  graphite,  molybdenite,  pyrrhotite,  mela- 
conite,  chalcocite,  ripidolite. 

PELHAM. — Steatite. 

PIERMONT. — Micaceous  iron,  barite,  green,  white,  and  brown  mica,  apatite,  titanic  iron. 

PLYMOUTH. — Columbite,  beryl. 

RICHMOND.— lolite  !  rutile,  steatite,  pyrite,  anthophyllite,  talc. 

RYE. — Chiastolite. 

SADDLEBACK  MT. — Black  tourmaline,  garnet,  spinel. 

SHELBURNE. — Galenite,  black  blende,  chalcopyrite,  pyrite,  pyrolusite. 

SPRINGFIELD.— Beryls  (very  large,  eight  inches  diameter),  manganesian  garnets!  black 
tourmaline  !  in  mica  slate,  albite,  mica. 

SULLIVAN. — Tourmaline  (black),  in  quartz,  beryl. 

SURREY. — Amethyst,  calcite,  galenite,  limonite,  tourmaline. 

SWANZEY  (near  Keene). — Magnetic  iron  (in  masses  in  granite). 

29 


450  APPENDIX. 

TAMWORTH  (near  White  Pond).—  G-alenite. 

UNITY  (estate  of  James  Neal). — Copper  and  iron  pyrites,  chlorophyllite,  green  mica,  radi- 
ated actinolite,  garnet,  titaniferous  iron  ore,  magnetite,  tourmaline. 

WALPOLE  (near  Bellows  Falls).— Made,  staurolite,  mica,  graphite. 

WARE  .—Graphite. 

WARREN.  —  Cfialcopyrite,  blende,  epidote,  quartz,  pyrite,  tremolite,  galenite,  rutile,  talc, 
molybdenite,  cinnamon  stone  !  pyroxene,  hornblende,  beryl,  cyanite,  tourmaline  (massive). 

WATERVILLE  . — Labradorite,  chrysolite. 

WESTMORELAND  (south  part). — Molybdenite!  apatite!  blue  feldspar,  bog  manganese  (north 
village),  quartz,  fluorite,  chalcopyrite,  oxide  of  molybdenum  and  uranium. 

WHITE  MTS.  (Notch  near  the  "Crawford  House"). — Green  octahedral  fluorite,  quartz 
crystals,  black  tourmaline,  chiastolite,  beryl,  calcite,  amethyst,  ainazonstone. 

WILMOT. — Beryl. 

WINCHESTER. — Pyrolusite,  rhodochrosite,  psilomelane,  magnetite,  granular  quartz,  spodu- 
mene. 

VERMONT. 

ADDISON. — Iron  sand,  pyrite. 

ALBURGH. — Quartz  crystals  on  calcite,  pyrite. 

ATHENS. — Steatite,  rhomb  spar,  actinolite,  garnet. 

BALTIMORE. — Serpentine,  pyrite  ! 

BARNET.  — Graphite. 

BELVIDERE. — Steatite,  chlorite. 

BENNINGTON. — Pyrolusite,  brown  iron  ore,  pipe  clay,  yellow  ochre. 

BERKSHIRE. — Epidote,  hematite,  magnetite. 

BETHEL. — Actinolite  !  talc,  chlorite,  octahedral  iron,  rutile,  brown  spar  in  steatite. 

BRANDON. — Braunite,  pyrolusite,  psilomelane,  limonite,  lignite,  white  clay,  statuary 
marble  ;  fossil  fruits  in  the  lignite,  graphite,  chalcopyrite. 

BRATTLEBOROTTGH. — Black  tourmaline  in  quartz,  mica,  zoisite,  rutile,  actinolite,  scapolite, 
spodumene,  roofing  slate. 

BRIDGEWATER. — Talc,  dolomite,  magnetite,  steatite,  chlorite,  gold,  native  copper,  blende, 
galenite,  blue  spinel,  chalcopyrite. 

BRISTOL. — Rutile,  limonite,  manganese  ores,  magnetite. 

BROOKFIELD.  — Arsenopyrite,  pyrite. 

CABOT.— Garnet,  staurolite,  hornblende,  albile. 

CASTLETON. — Roofing  slate,  jasper,  manganese  ores,  chlorite. 

CAVENDISH. — Garnet,  serpentine,  talc,  steatite,  tourmaline,  asbestus,  tremolite. 

CHESTER. — Asbestus,  feldspar,  chlorite,  quartz. 

CHITTENDEN. — Psilomelane,  pyrolusite,  brown  iron  ore,  hematite  and  magnetite,  galenite, 
iolite. 

COLCHESTER. — Brown  iron  ore,  iron  sand,  jasper,  alum. 

CORINTH. — Chalcopyrite  (has  been  mined),  pyrrhotite,  pyrite,  rutile,  quartz. 

COVENTRY.  —Rhodonite. 

CRAPTSBITRY. — Mica  in  concentric  balls,  calcite,  rutile. 

DERBY. — Mica  (adamsite). 

DUMMERSTON. — Rutile,  roofing  slate. 

FAIR  HAVEN.  — Roofing  slate,  pyrite. 

FLETCHER. — Pyrite,  magnetite,  acicular  tourmaline. 

GRAPTON. — The  steatite  quarry  referred  to  Graf  ton  is  properly  in  Athens  ;  quartz,  acti- 
nolite. 

GUTLFORD. — Scapolite,  rutile,  roofing  slate. 

HARTFORD. — Calcite,  pyrite!  cyanite  in  mica  slate,  quartz,  tourmaline. 

IRASBURGII. — Rhodonite,  psilomelane. 

JAY.  —  Chromic  iron,  serpentine,  amianthus,  dolomite. 

LOWELL. — Picrosmine,  amianthus,  serpentine,  cerolite,  talc,  chlorite. 

MARLBORO'. — Rhomb  spar,  steatite-,  garnet,  magnetite,  chlorite. 

MENDON. — Magnetic  iron  ore. 

MIDDLEBURY.  — Zircon. 

MIDDLESEX.— Rutile  !  (exhausted). 

MONKTON. — Pyrolusite,  brown  iron  ore,  pipe  clay,  feldspar. 

MORETOWN. — Smoky  quartz!  steatite,  talc,  wad,  rutile,  serpentine. 

MORRISTOWN.  — Galenite. 

MOUNT  HOLLY. — Asbestus,  chlorite. 

NEW  FANE.  —  Glassy  and  asbestif&rm  actinolite,  steatite,  green  quartz  (called  chrysoprase 


AMEKICAN   LOCALITIES.  451 

at  the  locality),  chalcedony,  drusy  quartz,  garnet,  chromic  and  titanic  iron,  rhomb  spar, 
serpentine,  rutile. 

NORWICH.— Actinolite,  feldspar,  brown  spar  in  talc,  cyanite,  zoisite,  chalcopyrite,  pyrite. 

PITTSFORD. — Brown  iron  ore,  manganese  ores. 

PLYMOUTH. — Siderite,  magnetite,  hematite,  gold,  galenite. 

PLYMPTON. — Massive  hornblende. 

PUTNEY. — Fluorite,  brown  iron  ore,  rutile,  and  zoisite,  in  boulders,  staurolite. 

READING. — Glassy  actinolite  in  talc. 

READS  BORO'. — Glassy  actinolite,  steatite,  hematite. 

RIPTON. — Brown  iron  ore,  augite  in  boulders,  octahedral  pyrite. 

ROCHESTER. — Rutile,  hematite  cryst. ,  magnetite  in  chlorite  slate. 

ROCKINGIIAM  (Bellows  Falls). — Cyanite,  indicolite,  feldspar,  tourmaline,  fluorite,  calcite, 
prehnite,  staurolite. 

ROXBURY. — Dolomite,  talc,  serpentine,  asbestus,  quartz. 

RUTLAND. — Magnesite,  white  marble,  hematite,  serpentine,  pipe  clay. 

SALISBURY. — Brown  iron  ore. 

SHARON. — Quartz  crystals,  cyanite. 

SHOREHAM. — Pyrite,  black  marble,  calcite. 

SHREWSBURY. — Magnetite  and  chalcopyrite. 

STARKSBORO'. — Brown  iron  ore. 

STIRLING. — Chalcopyrite,  talc,  serpentine. 

STOCKBRIDGE  — Arsenopyrite,  magnetite. 

STRAFPORD. — Magnetite  and  chalcopyrite  (has  been  worked),  native  copper,  hornblende, 
copperas. 

THETFORD. — Blende,  galenite,  cyanite,  chrysolite  in  basalt,  pyrrhotite,  feldspar,  roojing 
slate,  steatite,  garnet. 

TOWNSIIEND. — Actinolite,  black  mica,  talc,  steatite,  feldspar. 

TROY. — Magnetite,  talc,  serpentine,  picrosmine,  amianthus,  steatite,  one  mile  southeast  of 
village  of  South  Troy,  on  the  farm  of  Mr.  Pierce,  east  side  of  Missisco,  chromite,  zaratite. 

VERSHIRE. — Pyrite,  chalcopyrite,  tourmaline,  arsenopyrite,  quartz. 

WARDSBORO'. —  Zoisite,  tourmaline,  tremolite,  hematite. 

WARREN. — Actinolite,  magnetite,  wad,  serpentine. 

WATERBURY. — Arsenopyrite,  chalcopyrite,  rutile,  quartz,  serpentine. 

WATER VILLE. — Steatite,  actinolite,  talc. 

WEATHERSFIELD.  —Steatite,  hematite,  pyrite,  tremolite. 

WELLS'  RIVER. — Graphite. 

WESTFIELD. — Steatite,  chromite,  serpentine. 

WESTMINSTER. — Zoisite  in  boulders. 

WINDIIAM. — Glassy  actinolite,  steatite,  garnet,  serpentine. 

WOODBURY. — Massive  pyrite. 

WOODSTOCK.  —Quartz  crystals,  garnet,  zoisite. 

MASSACHUSETTS. 

ALFORD. — Galenite,  pyrite. 

ATHOL.— Allanite,  fibrolite  (?),  epidote!  babingtonite  ? 

A  UBU  RN.  — Masonite. 

BARRE.  —  Rutile  !  mica,  pyrite,  beryl,  feldspar,  garnet. 

GREAT  B ARRINGTON. — Tremolite. 

BEDFORD. —  Garnet. 

BELCHERTON. — Allanite. 

BERNARDSTON. — Magnetite. 

BEVERLY. — Columbite,  green  feldspar,  cassiterite. 

BLANFORD. — Serpentine,  antJwphyllite,  actinolite!  cJiromite,  cyanita,  rose  quartz  in 
boulders. 

BOLTON. — Scapolite!  pctalite,  spliene,  pyroxene,  nuttfilite,  diopside,  boltonite,  apatite,  mag- 
nesite,  rhomb  spar,  allanite,  yttrocerite !  cerium  ochre?  (on  the  scapolite),  spinel. 

BOXBOROUGH. — Scapolite,  spinel,  garnet,  augite,  actinolite,  apatite. 

BRIGHTON.  — Asbestus. 

BRIMFIELD  (road  leading  to  Warren). — lolite,  adularia,  molybdenite,  mica,  garnet. 

CARLISLE. — Tourmaline,  garnet!  scapolite,  actinolite. 

CHARLESTOWN.  —Prehnite,  laumontite,  stilbite,  chabazite,  quartz  crystals,  melanolite. 

CHELMSFORD. — Scapolite  (chelmsfordite),  chondrodite,  blue  spinel,  amianthus!  rose1 
quartz. 


452  APPENDIX. 

CHESTER. — Hornblende,  scapolite,  zoisite,  spodumene,  indicolite,  apatite,  magnetite,  chro- 
mite,  stiibite,  heulandite,  analcite  and  chabazite.  At  the  Emery  Mine,  Chester  Factories. — 
Corundum,  margarite,  diaspore,  epidote,  corundophilite,  chloritoid,  tourmaline,  menaccan- 
ite  !  rutile,  biotite,  mdianite  ?  andesite  ?  cyanite,  amesite. 

CHESTERFIELD. — Blue,  green,  and  red  tourmaline,  deavelandite  (albite),  lepidolite,  smoky 
quartz,  microlite,  spodumene,  cyanite,  apatite,  rose  beryl,  garnet,  quartz  crystals,  staurolite, 
cassiterite,  columbite,  zoisite,  uranite,  brookite  (eumanite),  scheelite,  anthophyllite,  bornite. 

CONWAY. — Pyrolusite,  fluorite,  zoisite,  rutile!  !  native  alum,  galenite. 

CUMMIN  GTON. — Rhodonite!  cummingtonite  (hornblende),  marcasite,  garnet. 

DEDIIAM. — Asbestus,  galenite. 

DEERPIELD. — Chabazite,  heulandite,  stiibite,  amethyst,  carnelian,  chalcedony,  agate. 

FITCHBURG  (Pearl  Hill). — Beryl,  staurolite!  garnets,  molybdenite. 

FOXBOROUGII. — Pyrite,  anthracite. 

FRANKLIN.  — Amethyst. 

GOSHEN. — Mica,  albite,  spodumene!  blue  and  green  tourmaline,  beryl,  zoisite,  smoky  quartz, 
columbite,  tin  ore,  galenite,  beryl  (goshenite),  pihlite  (cymatolite). 

GREENFIELD  (in  sandstone  quarry,  half  mile  east  of  village). — Allophane,  white  and 
greenish. 

HATFIELD.— Barite,  yellow  quartz  crystals,  galenite,  blende,  chalcopyrite. 

HAWLEY. — Micaceous  iron,  massive  pyrite,  magnetite,  zoisite. 

HEATH. — Pyrite,  zoisite. 

HINSDALE. — Brown  iron  ore,  apatite,  zoisite. 

HUBBARDSTON.  — Massive  pyrite. 

LANCASTER. — Cyanite,  chiastolite!  apatite,  staurolite,  pinite,  andalusite. 

LEE. — Tremolite!  sphene!  (east  part). 

LENOX. — Brown  hematite,  gibbsite(?) 

LEVERETT. — Barite,  galenite,  blende,  chalcopyrite. 

LEYDEN. — Zoisite,  rutile. 

LITTLEFIELD. — Spinel,  scapolite,  apatite. 

LYNNFIELD. — Magnesite  on  serpentine. 

MARTHA'S  VINEYARD. — Brown  iron  ore,  amber,  selenite,  radiated  pyrite. 

MENDON. — Mica!  chlorite. 

MIDDLEFIELD. — Glassy  actinolite,  rJiomb  spar,  steatite,  serpentine,  feldspar,  drusy  quartz, 
apatite,  zoisite,  nacrite,  chalcedony,  talc  !  deweylite. 

MILBURY. —  Vermiculite. 

MONTAGUE.  —Hematite. 

NEWBURY. — Serpentine,  chrysotile,  epidote,  massive  garnet,  siderite. 

NEWBURYPORT. — Serpentine,  nemalite,  uranite. — Argentiferous  galenite,  tetrahedrite, 
chalcopyrite,  pyrargyrite,  etc. 

NEW  BRAINTREE. — Black  tourmaline. 

NORWICH. — Apatite!  black  tourmaline,  beryl,  spodumene!  tnphylite  (altered),  blende, 
quartz  crystals,  cassiterite. 

NORTHFIELD.  —  Columbite,  fibrolite,  cyanite. 

PALMER  (Three  Rivers). — Feldspar,  prehnite,  calc  spar. 

PELHAM. — A.sbestus,  serpentine,  quartz  crystals,  beryl,  molybdenite,  green  hornstone,  epidote, 
amethvst,  corundum,  vermiculite  (pelhamite). 

PLAINFIELD. — Cummingtonite,, pyrolutite,  rhodonite. 

RICHMOND. — Brown  iron  ore,  gibbsite!  allophane. 

ROCKPORT. — Danalite,  cryophyllite,  annite,  cyrtoUte  (altered  zircon),  green  and  white  ortho- 
dase. 

ROWE. — Epidote,  talc. 

SOUTH  ROYALSTON. — Beryl!  !  (now  obtained  with  great  difficulty),  mica  /  f  feldspar/ 
allanite.  Four  miles  beyond  old  loc. ,  on  farm  of  Solomon  Hey  wood,  mica  !  beryl !  feldspar  ! 
menaccanite. 

RUSSEL.  — Schiller  spar  (diallage  ?),  mica,  serpentine,  beryl,  galenite,  chalcopyrite. 

SALEM. — In  a  boulder,  cancrinite,  sodalite,  elaeolite. 

SAUGUS. — Porphyry,  jasper. 

SHEFFIELD.— Asbestus,  pyrite,  native  alum,  pyrolusite,  rutile. 

SHELBURNE. — Rutile. 

SHUTESBURY  (east  of  Locke's  Pond). — Molybdenite. 

SOUTHAMPTON. —  Galenite,  cerussite,  anglesite,  wulfenite,  fluorite,  barite,  pyrite,  chalcopy- 
rite, blende,  corneous  lead,  pyromorphite,  stolzite,  chrysocolla. 

STERLING. — Spodumene,  chiastolite,  siderite,  arsenopyrite,  blende,  galenite,  chalcopyrite, 
pyrite,  sterlingite  (damourite). 

STONEHAM. — Nephrite. 


AMERICAN   LOCALITIES.  453 

STURBRTDGE.—  GrapJdte,  garnet,  apatite,  bog  ore. 

SWAMPSCOT. — Orthite,  feldspar. 

TAUNTON  (one  mile  south). — Paracolumbite  (titanic  iron). 

TURNER'S  FALLS  (Conn.  River).— Chalcopyrite,  prehnite,  chlorite,  chloropTweite,  siderite, 
malachite,  magnetic  iron  sand,  anthracite. 

TYRINGIIAM.  — Pyroxene,  scapolite. 

UXBRIDGE. — Galenite. 

WARWICK. — Massive  garnet,  radiated  black  tourmaline,  magnetite,  beryl,  epidote. 

WASHINGTON. — Graphite. 

WESTFIELD. — Schiller  spar  (diallage),  serpentine,  steatite,  cyanite,  scapolite,  actinolite. 

WESTFORD. — Andalusite  ! 

WEST  HAMPTON. — Galenite,  argentine,  pseudomorphous  quartz. 

WEST  SPRINGFIELD. — Prehnite,  ankerite,  satin  spar,  celestite,  bituminous  coal. 

WEST  STOCKBRIDGE  — Hematite,  fibrous  pyrolusite,  siderite. 

WIIATELY. — Native  copper,  galenite. 

WILLIAMSBURG.  — Zowite,  pseudomorphous  quartz,  apatite,  rose  and  smoky  quartz,  galenite, 
pyrolusite,  chalcopyrite. 

WILLIAMSTOWN.  —  Cry  (ft.  quartz. 

WINDSOR. — Zoisite,  actinolite,  rutilef 

WORCESTER. — Arsenopyrite,  idocrase,  pyroxene,  garnet,  amianthus,  bucholzite,  siderite, 
galenite. 

WORTHINGTON. — Cyanite. 

ZOAR. — Bitter  spar,  talc. 

RHODE  ISLAND. 

BRISTOL.  — Amethyst. 

COVENTRY. — Mica,  tourmaline. 

CRANSTON.  —Actinolite  in  talc,  graphite,  cyanite,  mica,  melanterite,  bog  iron. 

CUMBERLAND. — Manganese,  epidote,  actinolite,  garnet,  titaniferous  iron,  magnetite,  red 
hematite,  chalcopyrite,  bornite,  malachite,  azurite,  calcite,  apatite,  feldspar,  zoisite,  mica, 
quartz  crystals,  ilvaite. 

DIAMOND  HILL. — Quartz  crystals,  hematite. 

FOSTER. — Cyanite,  hematite. 

GLOUCESTER. — Magnetite  in  chlorite  slate,  feldspar. 

JOHNSTON. — Talc,  brown  spar,  calcite,  garnet,  epidote,  pyrite,  hematite,  magnetite,  chal- 
copyrite, malachite,  azurite. 

LIME  ROCK. — Calcite  crystals,  quartz  pyrite. 

LINCOLN. — Calcite  dolomite. 

NATIC. — See  WARWICK. 

NEWPORT. — Serpentine,  quartz  crystals. 

PORTSMOUTH  — Anthracite,  graphite,  asbestus,  pyrite,  chalcopyrite. 

SMITHFIELD. — Dolomite,  calcite,  bitter  spar,  siderite,  nacrite,  serpentine  (bowenite),  tremo- 
lite,  asbestus,  quartz,  magnetic  iron  in  chlorite  slate,  talc!  octahedrite,  feldspar,  beryl. 

VALLEY  FALLS. — Graphite,  pyrite,  hematite. 

WARWICK  (Natic  village). — Masonite,  garnet,  graphite,  bog  iron  ore. 

WESTERLY  . — Menaccanite . 

WOONSOCKET. — Cyanite. 

CONNECTICUT. 

BERLIN. — Barite,  datolite,  blende,  quartz  crystals. 

BOLTON. — Staurolite,  chalcopyrite. 

BRADLEY VILLE  (Litchfield). — Laumontite. 

BRISTOL. — Chalcocite!  chalcopyrite,  barite,  bornite,  talc,  aUophane,  pyromorphite,  calcite, 
malachite,  galenite,  quartz. 

BROOKFIELD. — Galenite,  calamine,  blende,  spodumene,  pyrrhotite. 

CANAAN. — Tremolite  and  white  augite!  in  dolomite,  canaanite  (massive  pyroxene). 

CHATHAM. — Arsenopyrite,  smaltite,  chloanthite  (ehathamite),  scorodite,  niccolite,  beryl, 
erythrite. 

CHESHIRE. — Barite,  chalcocite,  bornite  cryst.,  malachite,  kaolin,  natrolite,  prehnite,  chaba- ' 
zite,  datolite. 

CHESTER. — Sttlimanite!  zircon,  epidote. 


454  APPENDIX. 

CORNWALL.  —  Graphite,  pyroxene,  actinolite,  sphene,  scapolite. 

D  ANBURY. — Danburite,  oligoclase,  moonstone,  brown  tourmaline,  orthoclase.  pyroxene, 
parathorite. 

FARMINGTON. — Prehnite,  chabazite,  agate,  native  copper  ;  in  trap,  diabantite. 

GRANBY. — Green  malachite. 

GREENWICH.  — Black  tourmaline. 

H  ADD  AM. — Chrysoberyl  !  beryl!  epidote!  tourmaline!  feldspar,  garnet!  iolite!  oligodase, 
chlorophyllite !  automolite,  magnetite,  adularia,  apatite,  columbite!  (hermannolite),  zircon 
(calyptolite),  mica,  pyrite,  marcasite,  molybdenite,  allanite,  bismuth,  bismuth  ochre,  bismu- 
tite. 

HADLYME. — Chabazite  and  stilbite  in  gneiss,  with  epidote  and  garnet. 

HARTFORD. — Datolite  (Rocky  Hill  quarry). 

KENT. — Brown  iron  ore,  pyrolusite,  ochrey  iron  ore. 

LITCHFIELD. — Cyanite  with  corundum,  apatite,  and  andalusite,  menaccanite  (washington- 
ite),  chalcopyrite,  diaspore,  niccoliferous  pyrrhotite,  margarodite. 

LYME. — Garnet,  sunstone. 

MERIDEN.  — Datolite. 

MIDDLEFIELD  FALLS.  —  Datolite,  chlorite,  etc.,  in  amygdaloid. 

MIDDLETOWN. — Mica,  le-ptdoUtt  with,  green  and  red  tourmaline,  albite,  feldspar,  columbite! 
prehnite,  garnet  (sometimes  octahedral),  beryl,  topaz,  uranite,  apatite,  pitchblende  ;  at  lead 
mine,  gaienite,  cJudcopyrite,  blende,  quartz,  calcite,  fluorite,  pyrite,  sometimes  capillary. 

MILFORD. — Sahlite,  pyroxene,  asbestus,  zoisite,  verd-antique,  marble,  pyrite. 

NEW  HAVEN. — Serpentine,  asbestus,  chromic  iron,  sahlite,  stilbite,  prehnite,  chabazite, 
gmelinite,  apophyllite,  topazalite. 

NEWTOWN. — Cyanite^  diaspore,  rutile,  damourite,  cinnabar. 

NORWICH. — Sillimanite,  monazite  !  zircon,  iolite,  corundum,  feldspar. 

OXFORD,  near  Humphreys ville. — Cyanite,  chalcopyrite. 

PLYMOUTH. — Galenite,  heidandite,  fluorite,  chlorophyllite!  garnet. 

READING  (near  the  line  of  Danbury). — Pyroxene,  garnet. 

ROARING  BROOK  (Cheshire). — Dalolite  !  calcite,  prehnite,  saponite. 

ROXBURY. — Siderite,  blende,  pyrite!  !  gaienite,  quartz,  chalcopyrite,  arsenopyrite,  limon- 
ite. 

SALISBURY. — Brown  iron  ore,  ochrey  iron,  pyrolmite,  triplite,  turgite. 

SAYBROOK. — Molybdenite*  stilbite,  plumbago. 

SEYMOUR. — Native  bismuth,  arsenopyrite,  pyrite. 

SIMSBURY. — Copper  glance,  green  malachite. 

SOUTHBURY. — Rose  quartz,  laumontite,  prehnite,  calcite,  barite. 

SOUTHINGTON. — Barite,  datolite,  asteriated  quartz  crystals. 

STAFFORD. — Massive  pyrites,  alum,  copperas. 

STONINGTON. — Stilbite  and  chabazite  on  gneiss. 

TARIFFVILLE. — Datolite. 

THATCHERSVILLE  (near  Bridgeport). — Stilbite  on  gneiss,  babingtonite  ? 

TOLLAND. — Staurolite,  massive  pyrites. 

TRUMBULL  and  MONROE. — Chloropliane,  topaz,  beryl,  diaspore,  pyrrhotite,  pyrite,  nicco- 
lite,  scheelite,  wolframite  (pseudomorph  of  scheelite),  rutile,  native  bismuth,  tungstic  acid, 
siderite,  mispickel,  argentiferous  gaienite,  blende,  scapolite,  tourmaline,  garnet,  albite, 
augite,  graphic  tellurium  (V),  margarodite. 

WASHINGTON. — Triplite,  menaccanite!  (washingtonite  of  Shepard),  rhodochrosite,  natro- 
lite,  andalusite  (New  Preston),  cyanite. 

WATERTOWN,  near  the  Naugatuck. — White  sahlite,  monazite. 

WEST  FARMS. — Asbestus. 

WILLIMANTIC. — Topaz,  monazite,  ripidolite. 

WINCHESTER  and  WILTON. — Asbestus,  garnet. 


.  NEW  YORK. 

ALBANY  CO. — BETHLEHEM. — Calcite,   stalactite,   stalagmite,   calcareous  sinter,    snowy 
gypsum . 

COEYMAN'S  LANDING. — Gypsum,  epsom  salt,  quartz  crystals  at  Crystal  Hill,  three  miles 
south  of  Albany. 

.     G-UILDERLAND. — Petroleum,  anthracite,  and  calcite,  on  the  banks  of  the  Norman's  Kill, 
two  miles  south  of  Albany. 

WATERVLIET. — Quartz  crystals,  yellow  drusy  quartz. 


AMERICAN   LOCALITIES.  455 

ALLEGHANY  CO.— CUBA.— Calcareous  tufa,  petroleum,  3|  miles  from  the  village. 
CATT ARAUGUS  CO.  —FREEDOM.  —Petroleum. 

CAYUGA  CO.— AUBURN. — Celestite,  calcite,  fluorspar,  epsomite. 

CAYUGA  LAKE. — Sulphur. 

LUDLOWVILLE. — Epsomite. 

UNION  SPRINGS. — Selenite,  gypsum. 

SPRINGPORT. — At  Thompson's  plaster  beds,  sulphur/  selenite. 

SPRINGVILLE.  — Nitrogen  springs. 

CLINTON  CO. — ARNOLD  IRON  MINE. — Magnetite,  epidote,  molybdenite. 
FINCH  ORE  BED. —  Calcite,  green  and  purple  fluor. 

CHATAUQUE  CO.— FREDONIA. — Petroleum,  carburetted  hydrogen. 
L  AONA.  — Petroleum. 
SHERIDAN.  — Alum. 

COLUMBIA  CO. — AUSTERLITZ. — Earthy  manganese,  wulfenite,  chalcocite  ;  Livingston 
lead  mine,  vitreous  silver  ? 

CHATHAM. —Quartz,  pyrite  in  cubic  crystals  in  slate  (Hillsdale). 

CANAAN.— Chalcocite,  chalcopyrite. 

HUDSON. — Epidote,  selenite! 

NEW  LEBANON. — Nitrogen  springs,  graphite,  anthracite  ;  at  the  Ancram  lead  mine,  galen- 
ite,  barite,  blende,  wulfenite  (rare),  chalcopyrite,  calcareous  tufa ;  near  the  city  of  Hudson, 
epsom  salt,  brown  spar,  wad. 

DUT CHESS  CO. — AMENIA. — Dolomite,  limonite,  turgile. 
BECKMAN.  — Dolomite. 

DOVER. — Dolomite,  tremolite,  garnet  (Foss  ore  bed),  staurolite,  limonite. 
FISHKILL. — Dolomite ;  near  Peckville,  talc,  asbestus,  graphite,  hornblende,  augite,  actino- 
lite,  hydrous  anthophyllite,  limonite. 
NORTH  EAST. — Chalcocite,  chalcopyrite,  galenite,  blende. 
PAWLING.  — Dolomite. 

RIIINEBKCK. — Calcite,  green  feldspar,  epidote,  tourmaline. 
UNION  VALE. — At  the  Clove  mine,  gibbsite,  limonite. 

ESSEX  CO. — ALEXANDRIA. — Kir  by' s  graphite  mine,  graphite,  pyroxene,  scapolite,  sphene. 

CROWN  POINT. — Apatite  (eupyrchroite  of  Emmom),  brown  tourmaline!  in  the  apatite, 
chlorite,  quartz  crystals,  pink  and  blue  calcite,  pyrite ;  a  short  distance  south  of  J.  C.  Ham- 
mond's house,  garnet,  scapolite,  chalcopyrite,  aventurine  feldspar,  zircon,  magaetieiron  (Peru), 
epidote,  mica. 

KEKNE.— Scapolite. 

LEWIS. — Tabular  spar,  colopJionite,  garnet,  labradorite,  Jiornblende,  actinolite;  ten  miles 
south  of  the  village  of  Keeseville,  mispickel. 

LONG  POND. — Apatite,  garnet,  pyroxene,  idocrase,  coccolite!  !  scapolite,  magnetite,  blue 
calcite. 

MclNTYRE. — Labradorite,  garnet,  magnetite. 

MORIAII,  at  Sandford  Ore  Bed. — Magnetite,  apatite,  aUanite !  lanthanite,  actinolite,  and 
feldspar  ;  at  Fisher  Ore  Bed,  magnetic  iron,  feldspar,  quartz ;  at  Hall  Ore  Bed,  or  * '  New  Ore 
Bed,"  magnetite^  zircons;  on  Mill  brook,  calcite,  pyroxene,  hornblende,  albite;  in  the  town 
of  Moriah,  magnetite,  black  mica  ;  Barton  Hill  Ore  Bed,  albite. 

NEWCOMB. — Labradorite,  feldspar,  magnetite,  hypersthene. 

PORT  HENRY. — Brown  tourmaline,  mica,  rose  quartz,  serpentine,  green  and  black  pyroxene, 
hornblende,  cryst.  pyrite,  graphite,  wollastonite,  pyrrhotite,  adularia  ;  phlogopiie  !  at  Cheever 
Ore  Bed,  with  magnetite  and  serpentine. 

ROGER'S  ROCK. — Or  ophite,  wollastonite,  garnet,  colopJionite,  feldspar,  adularia,  pyroxene, 
sphene,  coccolite. 

SCHROON. —  Calcite,  pyroxene,  chondrodite. 

TICONDEROGA. — Graphite!  pyroxene,  sahlite,  sphene,  black  tourmaline,  cacoxene?  (Mt. 
Defiance). 

WESTPORT. — Labradorite,  prehnite,  magnetite. 

WILLSBORO'. —  Wollastonite,  colopJionite,  garnet,  green  coccolite,  hornblende. 

ERIE  CO. — ELLICOTT'S  MILLS. — Calcareous  tufas. 


456  APPENDIX. 

FRANKLIN  CO. — CHATEAUGAY. — Nitrogen  springs,  calcareous  tufas. 
MALONE. — Massive  pyrite,  magnetite. 

GENESEE  CO. — Acid  springs  containing  sulphuric  acid. 

GREENE  CO.  — C ATSKILL. —  Calcite. 
DIAMOND  HILL. — Quartz  crystals. 

HERKIMER  CO. — F AIRFIELD. — Quartz  crystals,  fetid  barite. 

LITTLE  FALLS. — Quartz  crystals?  barite,  calcite,  anthracite,  pearl  spar,  smoky  quartz; 
one  mile  south  of  Little  Falls,  calcite,  brown  spar,  feldspar. 

MIDDLEVILLE.  —  Quartz  crystals  !  calcite,  brown  and  pearl  spar,  anthracite. 
NEWPORT. — Quartz  crystals. 

SALISBURY. — Quartz  crystals  !  blende,  galenite,  pyrite,  chalcopyrite. 
STARK. — Fibrous  celestite,  gypsum. 

HAMILTON  CO.— LONG  LAKE.— Blue  calcite. 

JEFFERSON  CO. — ADAMS. — Fluor,  calc  tufa,  barite. 

ALEXANDRIA. — On  the  S.E.  bank  of  Muscolonge  Lake,  fluorite,  phlogopiU,  chalcopyrite, 
apatite ;  on  High  Island,  in  the  St.  Lawrence  River,  feldspar,  tourmaline,  hornblende,  ortho- 
clase,  celestite. 

ANTWERP. — Stirling  iron  mine,  hematite,  chalcodite,  siderite,  millerite,  red  hematite,  crys- 
tallized quartz,  yellow  aragonite,  niccoliferous  pyrite,  quartz  crystals,  pyrite  ;  at  Oxbow,  cal- 
cite !  porous  coralloidal  heavy  spar ;  near  Vrooman's  lake,  calcite !  vesuvianite,  phoogopite  ! 
pyroxene,  sphene^  fluorite,  pyrite,  chalcopyrite  ;  also  feldspar,  bog-iron  ore,  scapolite  (farm  of 
David  Eggleson),  serpentine,  tourmaline  (yellow,  rare). 

BROWNSVILLE. — Celestite  in  slender  crystals,  calcite  (four  miles  from  Watertown). 

NATURAL  BRIDGE. — Feldspar,  gieseckite  !  steatite  pseudomorphous  after  pyroxene,  apatite. 

NEW  CONNECTICUT. — Sphene,  brown  phlogopite. 

OMAR. — Beryl,  feldspar,  hematite. 

PHILADELPHIA. — Garnets  on  Indian  river,  in  the  village. 

PAMELIA. — Agaric  mineral,  calc  tufa. 

PIERREPONT. — Tourmaline,  sphene,  scapolite,  hornblende. 

PILLAR  POINT. — Massive  barite  (exhausted). 

THERESA. — Fluorite,  calcite,  hematite,  hornblende,  quartz  crystals,  serpentine  (associated 
with  hematite),  celestite,  strontianite  ;  the  Muscolonge  Lake  locality  of  fluoris  exhausted. 

WATERTOWN. — Tremolite,  agaric  mineral,  calc  tufa,  celestite. 

WILNA. — One  mile  north  of  Natural  Bridge,  calcite. 

LEWIS  CO. — DIANA  (localities  mostly  near  junction  of  crystalline  and  sedimentary  rocks, 
and  within  two  miles  of  Natural  Bridge) . — Scapolite  !  wollastonite,  green  coccolite,  feldspar, 
tremolite,  pyroxene  !  sphene.!  !  mica,  quartz  crystals,  drusy  quartz,  cryst.  pyrite,  pyrrhotite, 
blue  calcite,  serpentine,  rensselaerite,  zircon,  graphite,  chlorite,  hematite,  bog-iron  ore,  iron 
sand,  apatite. 

GREIG. — Magnetite,  pyrite. 

LOWVILLE. — Calcite,  fluorite,  pyrite,  galenite,  blende,  calc  tufa. 

MARTINSBURGH. — Wad,  galenite,  etc.,  but  mine  not  now  opened,  calcite. 

WATSON,  BREMEN. — Bog-iron  ore. 

MONROE  CO. — ROCHESTER. — Pearl  spar,  calcite,  snowy  gypsum,  fluor,  celestite,  galenite, 
blende,  barite,  hornstone. 

MONTGOMERY  CO.— CANAJOHARIE.  —Anthracite. 

PALATINE. — Quartz  crystals,  drusy  quartz,  anthracite,  hornstone,  agate,  garnet. 

ROOT. — Drusy  quartz,  blende,  barite,  stalactite,  stalagmite,  galenite,  pyrite. 

NEW  YORK  CO.— CORLEAR'S  HOOK.— Apatite,  brown  and  yellow  feldspar,  sphene. 

KINGSBRIDGE. — Tremolite,  pyroxene,  mica,  tourmaline,  pyrites,  rutile,  dolomite. 

HARLEM. — Epidote,  apophyilite,  stilbite,  tourmaline,  vivianite,  lamellar  feldspar,  mica. 

NEW  YORK. — Serpentine,  amianthus,  actinolite,  pyroxene,  hydrous  anthophyllite,  garnet, 
staurolite,  molybdenite,  graphite,  chlorite,  jasper,  necronite,  feldspar.  In  the  excavations  for 
the  4th  Avenue  tunnel,  1875,  harmotome,  stilbite,  chabazite,  heulandite,  etc. 


AMERICAN   LOCALITIES.  457 

NIAGARA  CO.—  LEWISTON.—  Epsomite. 

LOCKPORT. — Celestite,  calcite,  selenite,  anhydrite,  fluorite,  dolomite,  blende. 

NIAGARA  FALLS. — Calcite,  fluorite,  blende,  dolomite. 

ONEIDA  CO. — BOONVILLE. — Calcite,  wollastonite,  coccolite. 

CLINTON. — Blende,  lenticular  argillaceous  iron  ore;  in  rocks  of  the  Clinton  Group,  stronti- 
anite,  celestite,  the  former  covering  the  latter. 

ONONDAGA  CO. — CAMILLUS. — Selenite  and  fibrous  gypsum. 

COLD  SPUING. — Axinite. 

MANLIUS. — Gypsum  and  fluor. 

SYRACUSE. — Serpentine,  celestite,  selenite,  barite. 

ORANGE  CO. — CORNWALL. — Zircon,  chondrodite,  hornblende,  spinel,  massive  feldspar, 
fibrous  epidote,  hudsonite,  -menaccanite,- serpentine,  coccolite. 

DEER  PARK. — Cryst.  pyrite,  galenite. 

MONROE. — Mica!  sphene !  garnet,  colophonite,  epidote,  chondrodite,  allanite,  bucholzite, 
brown  spar,  spinel,  hornblende,  talc,  menaccanite,  pyrrhotite,  pyrite,  chromite,  graphite,  ras- 
tolyte,  moronolite. 

At  WILKS  and  O'NEIL  Mine  in  Monroe. — Aragonite,  magnetite,  dimagnetite  (pseud.  ?),  jen- 
kinsite,  asbestus,  serpentine,  mica,  hortonolile. 

At  Two  PONDS  in  Monroe.—  Pyroxene!  chondrodite,  Jwrnblende,  scapolite  !  zircon,  sphene, 
apatite. 

At  GREENWOOD  FURNACE  in  Monroe. — Chondrodite,  pyroxene  !  mica,  hornblende,  spinel, 
scapolite,  biotite!  menaccanite. 

At  FOREST  OP  DEAN. — Pyroxene,  spinel,  zircon,  scapolite,  hornblende. 

TOWN  OF  WARWICK,  WARWICK  VILLAGE. — Spinel!  zircon,  serpentine!  bi'own  spar,  pyrox- 
ene !  hornblende !  pseadomorphous  steatite,  feldspar !  (Rock  Hill),  menaccanite,  clintonite, 
tourmaline  (R.  H. ),  rutile,  sphene,  molybdenite,  arsenopyrite,  marcasite,  pyrite,  yellow  iron 
sinter,  quartz,  jasper,  mica,  coccolite. 

AMITY. — Spinel!  garnet,  scapolite,  hornblende,  vesuvianite,  epidote!  clintonite!  magnetite, 
tourmaline,  warwickite,  apatite,  chondrodite,  told  pyroxene!  rutile,  menaccanite,  zircon, 
corundum,  feldspar,  sphene,  calcite,  serpentine,  schiller  spar  (?),  silvery  mica. 

EOENVILLE. — Apatite,  chondrodite  !  hair-brown  hornblende  !  tremolite,  spinel,  tourmaline, 
warwickite,  pyroxene,  sphene,  mica,  feldspar,  mispickel,  orpiment,  rutile,  menaccanite,  scoro- 
dite,  chalcopyrite,  leucopyrite  (or  lollingite),  allanite. 

WEST  POINT. — Feldspar,  mica,  scapolite,  sphene,  hornblende,  allanite. 

PUTNAM  CO. — BREWSTER,  Tilly  Foster  Iron  Mine.  —  Chondrodite  /-(also  humite  andclino- 
humite)  crystals  very  rare,  magnetite,  dolomite,  serpentine  pseudomorphs,  brucite,  enstatite, 
ripidolite,  biotite,  actinolite,  apatite,  pyrrhotite,  fluorite,  albite,  epidote,  sphene. 

CARMEL  (Brown's  quarry). — Anthophyllite,  schiller  spar  (?),  orpiment,  arsenopyrite,  epi- 
dote. 

COLD  SPRING. — Chabazite,  mica,  sphene,  epidote. 

PATTERSON.—  Whit  t  pyroxene  !  calcite,  asbestus,  tremolite,  dolomite,  massive  pyrite. 

PIITLLIPSTOWN. — Tremolite,  amianthus,  serpentine,  sphene,  diopside,  green  coccolite,  horn- 
blende, scapolite,  stilbite,  mica,  laumontite,  gurhofite,  calcite,  magnetite,  chromite. 

PHILLIPS  Ore  Bed. — Hyalite,  actinolite,  massive  pyrite. 

RENSSELAER  CO. — Hoosic. — Nitrogen  springs. 
LANSINGBURGH. — Epsomite.  quartz  crystals,  pyrite. 
TROY.  —  Quartz  crystals,  pyrite,  selenite. 

RICHMOND  CO. — ROSSVILLE. — Lignite,  cryst.  pyrite. 

QUARANTINE. — Asbestus,  amianthus,  aragonite,  dolomite,  gurhofite,  brucite,  serpentine, 
talc,  magnesite. 

ROCKLAND  CO.— CALDWELL.— Calcite. 

GRASSY  POINT. — Serpentine,  actinolite. 

HAVERSTRAW.  —Hornblende,  barite. 

LADENTOWN. — Zircon,  malachite,  cuprite. 

PIERMONT. — Datolite,  stilbite,  apophyllite,  stellite,  prehnite,  thomsonite,  calcite,  chabazite. 

STONY  POINT.— Cerolite,  lamellar  hornblende,  asbestus. 


458  APPENDIX. 

ST.  LAWRENCE  CO.— CANTON.—  Massive  pyrite,  calcite,  brown  tourmaline,  sphene,  ser- 
pentine, talc,  rensselaerite,  pyroxene, "hematite,  chalcopyrite. 

DEKALB. — Hornblende,  barite,  fluorite,  tremolite,  tourmaline,  blende,  graphite,  pyroxene, 
quartz  (spongy),  serpentine. 

EDWARDS.  —Brown  and  silvery  mica  !  scapolite,  apatite,  quartz  crystals,  actinolite,  tremo- 
lite !  hematite,  serpentine,  magnetite. 

FINE. — Black  mica,  hornblende. 

FOWLER. — Barite,  quartz  crystals!  hematite,  blende,  galenite,  tremolite,  chalcedony,  bog 
ore,  satin  spar  (assoc.  with  serpentine),  pyrite,  chalcopyrite,  actinolite,  rensselaerite  (near 
Somerville). 

GOUVERNEUR. —  Calcite !  serpentine!  JiornUende!  scapolite!  ortfwclase,  tourmaline!  ido- 
crase  (one  mile  south  of  G-.),  pyroxene,  malacolite,  apatite,  rensselaerite,  serpentine,  sphene, 
fluorite,  barite  (farm  of  Judge  Dodge),  black  mica,  phlogopite,  tremolite  !  asbestus,  hematite, 
graphite,  vesuvianite  (near  Somerville  in  serpentine),  spinel,  houghite,  scapolite,  phlogopite, 
dolomite  ;  three-quarters  of  a  mile  west  of  Somerville,  chondrodite,  spinel ;  two  miles  north 
of  Somerville,  apatite,  pyrite,  brown  tourmaline!  ! 

HAMMOND. — Apatite!  zircon!  (farm  of  Mr.  Hardy),  w^ctoe(loxocase),  pargasite,  barite, 
pyrite,  purple  fluorite,  dolomite. 

HERMON. — Quartz  crystals,  hematite,  siderite,  pargasite,  pyroxene,  serpentine,  tourma- 
line, bog-iron  ore. 

MACOMB. — Blende,  mica,  galenite  (on  land  of  James  Averil),  sphene. 

MINERAL  POINT,  Morristown. — Fluorite,  blende,  galenite,  phlogopite  (Pope's  Mills),  barite. 

OGDENSBURG.  — Labradorite. 

PITCAIRN. — Satin  spar,  associated  with  serpentine. 

POTSDAM. — Hornblende! — eight  miles  from  Potsdam,  on  road  to  Pierrepont,  feldspar, 
tourmaline,  black  mica,  hornblende. 

KOSSIE  (Iron  Mines). — Barite,  hematite,  coralloidal  aragonite  in  mines  near  Somerville, 
limonite,  quartz  (sometimes  stalactitic  at  Parish  iron  mine),  pyrite,  pearl  spar. 

ROSSIE  Lead  Mine. — Calcite!  galenite!  pyrite,  celestite,  chalcopyrite,  hematite,  cerussite, 
anglesite,  octahedral  fluor,  black  phlogopite. 

Elsewhere  in  ROSSIE.  —  Calcite,  barite,  quartz  crystals,  chondrodite  (near  Yellow  Lake), 
feldspar  !  pargasite !  apatite,  pyroxene,  hornblende,  sphene,  zircon,  mica,  fluorite,  serpen- 
tine, automolite,  pearl  spar,  graphite. 

KUSSEL. — Pargasite,  specular  iron,  quartz  (dodec.),  calcite,  serpentine,  rensselaerite, 
magnetite. 

SARATOGA  CO. — GREENFIELD. — Chrysoberyl!  garnet!  tourmaline!  mica,  feldspar  t 
apatite,  graphite,  aragonite  (in  iron  mines). 

SCHOHARIE  CO.— BALL'S  CAVE,  and  others.— Calcite,  stalactites. 

CARLISLE. — Fibrous  barite,  cryst.  and  jib.  calcite. 

MIDDLEBURY. — Anthracite,  calcite. 

SHARON. — Calcareous  tufa. 

SCHOHARIE. — Fibrous  celestite,  strontianite  !  cryst.  pyrite  ! 


SENECA  CO. — CANOGA. — Nitrogen 

SULLIVAN  CO. — WURTZBORO'. — Galenite,  blende,  pyrite,  chalcopyrite. 

TOMPKINS  CO  —ITHACA.— Calcareous  tufa. 

ULSTER  CO. — ELLENVILLE. — Galenite,  blende,  chalcopyrite  !  quartz,  brookite. 
MARBLETOWN. — Pyrite. 

WARREN  CO.—  CALDWELL.—  Massive  feldspar. 

CHESTER. — Pyrite,  tourmaline,  rutile,  chalcopyrite. 

DIAMOND  ISLE  (Lake  George).  —  Galcile,  quartz  crystals. 

GLENN'S  FALLS. — Rhomb  spar.  *  ,. 

JOHNSBURG. — Fluorite  !  zircon  !  !  graphite,  serpentine,  pyrite. 

WASHINGTON  CO.— FORT  ANN.— Graphite,  serpentine. 
GRANVILLE. — Lamellar  pyroxene,  massive  feldspar,  epidote. 

WAYNE  CO.— WOLCOTT.—  Barite. 


AMERICAN   LOCALITIES.  459 

WESTCHESTFR  CO.— ANTHONY'S  NOSE.— Apatite,  pyrite,  calcite!  in  very  large  tabular 
crystals,  grouped,  and  sometimes  incrusted  with  drusy  quartz. 

DAVENPORT'S  NECK. — Serpentine,  garnet,  sphene. 

EASTCHESTEK.—  Blende,  pyrite,  chalcopyrite,  dolomite. 

H A ST ING  s.  — -2 'remolite,  white  pyroxene. 

NEW  ROCHELLE. — Serpentine,  brucite,  quartz,  mica,  tremolite,  garnet,  magnesite. 

PEEKSKILL. — Mica,  feldspar,  hornblende,  stilbite,  sphene;  three  miles  south,  emery. 

RYE. — Serpentine,  chlorite,  black  tourmaline,  tremoli-te. 

SINGSING. — Pyroxene,  tremolite,  pyrite,  beryl,  azurite,  green  malachite,  cerussite,  pyromor- 
phite,  anglesite,  vauquelinite,  galenite,  native  silver,  chalcopyrite. 

WEST  FAKMS. — Apatite,  tremolite,  garnet,  stilbite,  heulandite,  chabazite,  epidote,  sphene. 

YONKERS. — Tremolite,  apatite,  calcite,  analcite,  pyrite,  tourmaline. 

YORKTOWN. — Sillimanite,  monazite,  magnetite. 

NEW  JERSEY. 

ANDOVER  IRON  MINE  (Sussex  Co.). — Willemite,  brown  garnet. 

ALLEN  TOWN  (Monmouth  Co.). —  Vivianite,  dufrenite. 

BELVILLE. — Copper  mines. 

BERGEN. — Calcite!  datolite!  pectolite  (called  stellite) !  analcite,  apophyllite!  gmelinite, 
prehnite,  sphene,  stilbite,  natrolite,  heulandite,  laumontite,  cliabazite,  pyrite,  pseudomorphous 
steatite,  imitative  of  apophyllite,  diabantite. 

BRUNSWICK. — Copper  mines;  native  copper,  malachite,  mountain  leather. 

BRYAM.— Chondrodite,  spinel,  at  Roseville,  epidote. 

CANTWELL'S  BRIDGE  (Newcastle  Co.),  three  miles  west. — Vivianite. 

DANVILLE  (Jemmy  Jump  Ridge). — Graphite,  chondrodite,  augite,  mica. 

FLEMINGTON. — Copper  mines. 

FRANKFORT.  — Serpentine. 

FRANKLIN  and  STERLING. — Spinel!  garnet!  rJiodonitf. !  willemite !  franklinite  !  zincite  ! 
dyslwite!  hornblende,  tremolite,  chondrodite,  white  scapolite,  black  tourmaline,  epidote,  pink 
calcite,  mica,  actinolite,  augite,  sahlite,  coccolite,  asbestus,  jeffersonite  (augite),  calamine, 
graphite,  fluorite,  beryl,  galenite,  serpentine,  honey-colored  sphene,  quartz,  chalcedony, 
amethyst,  zircon,  molybdenite,  vivianite,  tephroite,  rhodochrosite,  aragonite,  sussexite,  chal- 
cophanifce,  roepperite,  calcozincite,  vanuxemite,  gahnite.  Also  algerite  in  gran,  limestone. 

FRANKLIN  and  WARWICK  MTS. — Pyrite. 

GREENBROOK. — Copper  mines. 

GRIGGSTOWN. — Copper  mines. 

HAMBURGH. — One  mile  north,  spinel!  tourmaline,  phlogopite,  hornblende,  limonite,  hematite. 

HOBO  KEN. — Serpentine  (marmolite),  brucite,  nemalite  (or  fibrous  brucite),  aragonite,  dolo- 
mite. 

HURDSTOWN. — Apatite,  pyrrhotite,  magnetite. 

IMLEYTOWN. — Vivianite. 

LOCK  WOOD. — Graphite,  chondrodite,  talc,  augite,  quartz,  green  spinel. 

MONTVILLE  (Morris  Co.). — Serpentine,  chrysolite. 

MULLICA  HILL  (Gloucester  Co.). —  Vivianite  lining  belemnites  and  other  fossils. 

NEWTON. — Spinel,  blue,  pink,  and  white  corundum,  mica,  vesuvianite,  hornblende,  tourma- 
line, scapolite,  rutile,  pyrite,  talc,  calcite,  barite,  pseudomorphous  steatite. 

PATERSON. — Datolite. 

VERNON. — Serpentine,  spinel,  hydrotalcite. 

PENNSYLVANIA.* 
ADAMS  CO. — GETTYSBURG. — Epidote,  fibrous  and  massive. 

BERKS  CO. — MORGANTOWN. — At  Jones's  mines,  one  mile  east  of  Morgantown,  green 
malachite,  native  copper,  chrysocolla,  magnetite,  allophane,  pyrite,  chalcopyrite,  aragonite, 
apatite,  talc ;  two  miles  N.E.  from  Jones's  mine,  graphite,  sphene;  at  Steele's  mine,  one 
mile  N.W.  from  St.  Mary's,  Chester  Co.,  'magnetite,  micaceous  iron,  coccolite,  brown  garnet. 

READING. — Smoky  quartz  crystals,  zircon,  stilbite,  iron  ore,  near  Pricetown,  zircon,  allan- 
ite,  epidote ;  at  Eckhardt's  Furnace,  allanite  with  zircon  ;  at  Zion's  Church,  molybdenite  ; 

*  See  also  the  Report,  on  the  Mineralogy  of  Pennsylvania,  by  Dr.  F   A.  Genth,  1875. 


460  APPENDIX. 

near  Kutztown,  in  the  Crystal  Cave,  stalactites ;  at  Fritz  Island,  apophyttite,  thomsonite,  chaba- 
zite,  calcite,  azurite,  malachite,  magnetite,  chalcopyrite,  stibnite,  prochlorite,  precious  ser- 
pentine. 

BUCKS  CO.— BUCKINGHAM  TOWNSHIP.—  Crystallized  quartz;  near  New  Hope,  vesuvian- 
ite,  epidote,  barite. 

SOUTHAMPTON. — Near  the  village  of  Feasterville,  in  the  quarry  of  George  Van  Arsdale, 
graphite,  pyroxene,  sahlite,  coccolite,  sphene,  green  mica,  calcite,  wottastonite,  glassy  feld- 
spar sometimes  opalescent,  phlogopite,  blue  quartz,  garnet,  zircon,  pyrite,  moroxite,  scapolite. 

NEW  BRITAIN. — Dolomite,  galenite,  blende,  malachite. 

CHESTER  CO. — AVONDALE.— Asbestus,  tremolite,  garnet,  opal. 
CARBON  CO. — SUMMIT  HILL,  in  coal  mines. — Kaolinite. 

BIRMINGHAM  TOWNSHIP. — Amethyst,  smoky  quartz,  serpentine,  beryl ;  in  Ab'm  Darling- 
ton's lime  quarry,  calcite. 

EAST  BRADFORD. — Near  Buffington's  bridge,  on  the  Brandywine,  green,  blue,  and  gray 
cyanite,  the  gray  cyanite  is  found  loose  in  the  soil,  in  crystals  ;  on  the  farms  of  Dr.  Elvvyn, 
Mrs.  Foulke,  Wm.  Gibbons,  and  Saml.  Entrikin,  amethyst.  At  Strode's  mill,  asbestus,  mag- 
netite, anthophyllite,  epidote,  aquacrepitite,  oligoclase,  drusy  quartz,  collyrite?  on  Os- 
borne's  Hill,  wad,  manganesmn  garnet  (massive),  sphene,  schorl ;  at  Caleb  Cope's  lime  quarry, 
fetid  dolomite,  necronite,  garnets,  blue  cyanite,  yellow  actinolite  in  talc ;  near  the  Black 
Horse  Inn,  indurated  talc,  rutile ;  on  Amor  Davis'  farm,  orthite!  massive,  from  a  grain  to 
lumps  of  one  pound  weight ;  near  the  paper-mill  on  the  Brandywine,  zircon,  associated  with 
titaniferous  iron  in  blue  quartz. 

WEST  BRADFORD. — Near  the  village  of  Marshalton,  green  cyanite,  rutile,  scapolite,  pyrite, 
staurolite ;  at  the  Chester  County  Poor-house  limestone  quarry,  chesterlite !  in  crystals  im- 
planted on  dolomite,  rutile  !  in  brilliant  acicular  crystals,  which  are  finely  terminated,  cal- 
cite in  scalenohedrons,  zoisite,  damourite  f  in  radiated  groups  of  crystals  on  dolomite,  quartz 
crystals  ;  on  Smith  &  McMullin's  farm,  epidote. 

CHARLESTOWN. — Pyromorphite,  cerussite,  galenite,  quartz. 

COVENTRY. — Allanite,  near  Pughtown. 

SOUTH  COVENTRY. — In  Chrisman's  limestone  quarry,  near  Coventry  village,  augitc, 
sphene,  graphite,  zircon  in  iron  ore  (about  half  a  mile  from  the  village). 

EAST  FALLOWFIELD.— Soapstone. 

EAST  GOSHEN. — Serpentine,  asbestus,  magnetite  (loadstone),  garnet. 

ELK. — Menaccanite  with  muscovite,  chromite  ;  at  Lewisville,  black  tourmaline. 

WEST  GOSHEN. — On  the  Barrens,  one  mile  north  of  West  Chester,  amianthus,  serpentine, 
cellular  quartz,  jasper,  chalcedony,  drusy  quartz,  chlorite,  marmolite,  indurated  talc,  mag- 
nesite  in  radiated  crystals  on  serpentine,  hematite,  asbestus  ;  near  R.  Taylor's  mill,  chromite 
in  octahedral  crystals,  dewcylite,  radiated  magnesite,  aragonite,  staurolite,  garnet,  asbestus, 
epidote;  zoisite  on  hornblende  at  West  Chester  water- works  (not  accessible  at  present). 

NEW  GARDEN. — At  Nivin's  limestone  quarry,  brown  tourmaline,  necronite,  scapolite,  apa- 
tite, brown  and  green  mica,  rutile,  aragonite,  fibrolite,  kaolinite,  tremolite. 

KENNETT. — Actinolite,  brown  tourmaline,  browu  mica,  epidote,  tremolite,  scapolite,  ara- 
gonite ;  on  Wm.  Cloud's  farm,  sunstone!  !  chabazite,  sphene.  At  Pearce's  old-mill,  zoisite, 
epidote,  sunstone  ;  sunstone  occurs  in  good  specimens  at  various  places  in  the  range  of  horn- 
blende rocks  running  through  this  township  from  N.E.  to  S.W. 

LOWER  OXFORD. — Garnets,  pyrite  in  cubic  crystals. 

LONDON  GROVE. — Rutile,  jasper,  chalcedony  (botryoidal),  large  and  rough  quartz  crystals, 
epidote  ;  on  Wm.  Jackson's  farm,  yellow  and  black  tourmaline,  tremolite,  rutile,  green  mica, 
apatite,  at  Pusey's  quarry,  rutile,  tremolite. 

EAST  MARLBOROUGH. — On  the  farm  of  Baily  &  Brothers,  one  mile  south  of  Unionville, 
bright  yellow  and  nearly  white  tourmaline,  chesterlite,  albite,  pyrite  ;  near  Marlborough  meet- 
ing-house, epidote,  serpentine,  acicular  black  tourmaline  in  white  quartz ;  zircon  in  small 
perfect  crystals,  loose  in  the  soil  at  Pusey's  saw-mill,  two  miles  S.W.  of  Unionville. 

WEST  MARLBOROUGH.  — Near  Logan's  quarry,  staurolite,  cyanite,  yellow  tourmaline,  rutile, 
garnets ;  near  Doe  Run  village,  hematite,  scapolite,  tremolite  ;  in  R.  Baily's  limestone  quarry, 
two  and  a  half  miles  S.W.  of  Unionville,  jibrous  tremolite,  cyanite,  scapolite. 

NEWLIN.— On  the  serpentine  barrens,  one  and  a  half  mile  N.E.  of  Unionville,  corundum! 
massive  and  crystallized,  also  in  crystals  in  albite,  often  in  loose  crystals  covered  with  a  thin 
coating  of  steatite,  spinel  (black),  talc,  picrolite,  brucite,  green  tourmaline  with  flat  pyram- 
idal terminations  in  albite,  unionite  (rare)  euphyllite,  mica  in  hexagonal  crystals,  feldspar, 


AMERICAN   LOCALITIES.  461 

beryl!  in  hexagonal  crystals,  one  of  which  weighs  51  Ibs.,  pyrite  in  ccbic  crystals,  chromic 
iron,  drusy  quartz,  green  quartz,  actinolite,  emerylite,  chloritoid,  diallage,  oligoclase;  on 
Johnson  Patterson's  farm,  massive  corundum,  titaniferous  iron,  dinoclilore,  emerylite, 
sometimes  colored  green  by  chrome,  albite,  orthoclase,  halloysite,  margarite,  garnets,  beryl; 
on  J.  Lesley's  farm,  corundum,  crystallized  and  in  massive  lumps,  one  of  which  weighed 
5,200  Ibs.,  diaspore  !  !  emerylite!  euphyllite  crystallized!  green  tourmaline,  transparent 
crystals  in  the  euphyllite.  orthoclase ;  two  miles  N.  of  Unionville,  magnetite  in  octahedral 
crystals;  one  mile  E.  of  Unionville,  hematite;  in  Edwards's  old  limestone  quarry,  purple 
fluorite,  rutile. 

EAST  NOTTINGHAM. — Sand  chrome,  asbestus,  chromite  in  octahedral  crystals,  hallite,  beryl. 

WEST  NOTTINGHAM. — At  Scott's  chrome  mine,  chromite,  foliated  talc,  marmolite,  serpen- 
tine, chalcedony,  rhodochrome ;  near  Moro  Phillip's  chrome  mine,  asbestus  ;  at  the  magnesia 
quarry,  dew  ey  lite,  marmolite,  magnesite,  leelite,  serpentine,  sand  chrome;  near  Fremont 
P.O.,  corundum. 

EAST  PIKELAND. — Iron  ore. 

WEST  PIKELAND. — In  the  iron  mines  near  Chester  Springs,  gibbsite,  zircon,  turgite,  hema- 
tite (stalactitical  and  in  geodes),  gothite. 

PENN. — Garnets,  agalmatolite. 

PENNSBURY. — On  John  Craig's  farm,  brown  garnets,  mica  ;  on  J.  Dilworth's  farm,  near 
Fairville,  muscovite  !  in  hexagonal  prisms  from  one-quarter  to  seven  inches  in  diameter  ;  in 
the  village  of  Fairville,  sunstone  ;  near  Brinton's  ford,  on  the  Brandy  wine,  chondrodite,  sphene, 
diopside.  augite.  coccolite ;  at  Mendenhall's  old  limestone  quarry,  fetid  quartz,  sunstone  ;  at 
Swain's  quarry,  crystals  of  orthoclase. 

POCOPSON. — On  the  farms  of  John  Entrikin  and  Jos.  B.  Darlington,  amethyst. 

SADSBURY. — Rutile!!  splendid  geniculated  crystals  are  found  loose  in  the  soil  for  seven 
miles  along  the  valley,  and  particularly  near  the  village  of  Parkesburg,  where  they  sometimes 
occur  weighing  one  pound,  doubly  geniculated  and  of  a  deep  red  color ;  near  Sadsbury  village, 
amethyst,  tourmaline,  epidote,  milk  quartz. 

SCHUYLKILL. — In  the  railroad  tunnel  at  PHCENIXVILLE,  dolomite!  sometimes  coated  with 
pyrite,  quartz  crystals,  yellow  blende,  brookite,  calcite  in  hexagonal  crystals  enclosing  pyrite  ; 
at  the  WHEATLEY,  BROOKDALE,  and  CHESTER  COUNTY  LEAD  MINES,  one  and  a  half  mile 
S.  of  Phoenixville,  pyromorpJiite!  cerussite!  galenite,  anglezite!  !  quartz  crystals,  chalcopy- 
rite,  barite,  fluorite  (white),  stolzite,  wulfenite!  calamine,  vanadinite,  blende/  mimetite! 
descloizite,  gothite,  chrysocolla,  native  copper,  malachite,  azurile,  liinonite,  calcite,  sulphur, 
pyrite,  melaconite,  pseudomalachite,  gersdorffite,  chalcocite  ?  covellite. 

TIIORNBURY. — On  Jos.  H.  Brinton's  farm,  muscovite  containing  acicular  crystals  of  tour- 
maline, rutile,  titaniferous  iron. 

TREDYFFRIN. — Pyrite  in  cubic  crystals  loose  in  the  soil. 

UWCHLAN. — Massive  blue  quartz,  graphite. 

WARREN. — Melanite,  feldspar. 

WEST  GrOSHEN  (one  mile  from  West  Chester). — Chromite. 

WILLISTOWN. — Magnetite,  chromite,  actinolite,  asbestus. 

WEST-TOWN. — On  the  serpentine  rocks,  3  miles  S.  of  West  Chester,  dinoc?dore  !  jefferisite  ! 
mica,  asbestus,  actinolite,  magnesite,  talc,  titaniferous  iron,  magnetite  and  massive  tourma- 
line. 

EAST  WHITELAND. — Pyrite,  in  very  perfect  cubic  crystals,  is  found  on  nearly  every  farm 
in  this  township,  quartz  crystals  found  loose  in  the  soil. 

WEST  WHITELAND. — At  Gen.  Trimble's  iron  mine  (south-east),  stalactitic  hematite! 
wavellite!  !  in  radiated  stalactites,  gibbsite,  cceruleolactile. 

WARWICK. — At  the  Elizabeth  mine  and  Keim's  old  iron  mine  adjoining,  one  mile  N.  of 
Knauertown,  aplome  garnet!  in  brilliant  dodecahedrons,  flosferri,  pyroxene,  micaceous  hema- 
tite, pyrite  in  bright  octahedral  crystals  in  calcite,  chrysocolla,  chalcopyrite  massive  and  in 
single  tetrahedral  crystals,  magnetite,  fascicular  hornblende!  bornite,  malachite,  brown  garnet, 
calcite,  byssolite !  serpentine ;  near  the  village  of  St.  Mary's,  magnetite  in  dodecahedral 
crystals,  melanite,  garnet,  actinolite  in  small  radiated  nodules ;  at  the  Hopewell  iron  mine, 
one  mile  N.W.  of  St.  Mary's,  magnetite  in  octahedral  crystals. 

COLUMBIA  CO. — At  Webb's  mine,  yellow  blende  in  calcite ;  near  Bloomburg,  cryst.  mag- 
netite. 

DAUPHIN  CO. — NEAK  HUMMERSTOWN. — Green  garnets,  cryst.  smoky  quartz,  feldspar. 

DELAWAEE  CO. — ASTON  TOWNSHIP. —  Amethyst,  corundum,  emerylite,  staurolite,  fibro- 
lite,  black  tourmaline,  margarite,  sunstone,  asbestus,  anthophyllite,  steatite;  near  Tyson's 
mill,  garnet,  staurolite  j  at  Peter's  mill-dam  in  the  creek,  pyrope  garnet. 


462  APPENDIX. 

BIRMINGHAM. — Fibrolite,  kaolin  (abundant),  crystals  of  rutile,  amethyst;  at  Bullock's  old 
quarry,  zircon,  bucholzite,  nacrite,  yellow  crystallized  quartz,  feldspar. 

BLUE  HILL. — Green  quartz  crystals,  spinel. 

CHESTER. — Amethyst,  black  tourmaline,  beryl,  crystals  of  feldspar,  garnet,  cryst.  pyrite, 
molybdenite,  molybdite,  chalcopyrite,  kaolin,  uraninite,  muscovite,  orthoclase,  bismutite. 

CHICHESTER.— Near  Trainer's  mill-dam,  beryl,  tourmaline,  crystals  of  feldspar,  kaolin;  on 
Win.  Eyre's  farm,  tourmaline. 

CONCORD.  —  Crystals  of  mica,  crystals  of  feldspar,  kaolin  abundant,  drusy  quartz  of  a  blue 
and  green  color,  meerschaum,  stellated  tremolite,  some  of  the  rays  6|  in.  diameter,  antho- 
pliyllite,  fibrolite,  acicular  crystals  of  rutile,  pyrope  in  quartz,  amethyst,  actinolite,  mangane- 
sian  garnet,  beryl  ;  in  Green's  creek,  pyrope  gat  net. 

DARBY. — Blue  and  gray  cyanite,  garnet,  staurolite,  zoisite,  quartz,  beryl,  chlorite,  mica, 
limonite. 

EDGEMONT. — Amethyst,  oxide  of  manganese,  crystals  of  feldspar  ;  one  mile  east  of  Edge 
mont  Hall,  rutile  in  quartz. 

GREEN'S  CREEK. — Garnet  (so-called  pyrope). 

HAVERFORD. — Staurolite  with  garnet. 

MARPLE. — Tourmaline,  andalusite,  amethyst,  actinolite,  anthophyllite,  talc,  radiated  actin- 
olite in  talc,  chromite,  drusy  quartz,  beryl,  cryst.  pyrite,  menaccanite  in  quartz,  chlorite. 

MIDDLETOWN. — Amethyst,  beryl,  black  mica,  mica  with  reticulated  magnetite  between  the 
plates,  manganesian  garnets  !  large  trapezohedral  crystals,  some  3  in.  in  diameter,  indurated 
talc,  hexagonal  crystals  of  rutile,  crystals  of  mica,  green  quartz  !  anthophyllite,  radiated-  tour- 
maline, staurolite,  titanic  iron,  fibrolite,  serpentine ;  at  Lenni,  chlorite,  green  and  bronze 
vermiculite  !  green  feldspar  ;  at  Mineral  Hill,  fine  crystals  of  corundum,  one  of  which  weighs 
If  lb.,  actinolite  in  great  variety,  bronzite,  green  feldspar,  moonstone,  sunstone,  graphic 
granite,  magnesite,  octahedral  crystals  of  chromite  in  great  quantity,  beryl,  chalcedony, 
asbestus,  fibrous  hornblende,  rutile,  staurolite,  melanosiderite,  hallite ;  at  Painter's  Farm, 
near  Dismal  Run,  zircon  with  oligoclase,  tremolite,  tourmaline ;  at  the  Black  Horse,  near 
Media,  corundum  ;  at  Hibbard's  Farm  and  at  Fairlamb's  Hill,  chromite  in  brilliant  octahe- 
drons. 

NEWTOWN. — Serpentine,  hematite,  enstatite,  tremolite. 

UPPER  PROVIDENCE. — Anlhophyllite,  tremolite,  radiated  asbestus,  radiated  actinolite,  tour- 
maline, beryl,  green  feldspar,  amethyst  (one  found  on  Morgan  Hunter's  farm  weighing  over  7 
Ibs.),  andalusite  !  (one  terminated  crystal  found  on  the  farm  of  Jas.  Worrall  weighs  7|  Ibs.)  ; 
at  Blue  Hill,  very  fine  crystals  of  blue  quartz  in  chlorite,  amianthus  in  serpentine,  zircon. 

LOWER  PROVIDENCE.—  Amethyst,  green  mica,  garnet,  large  crystals  of  feldspar!  (some 
over  100  Ibs.  in  weight). 

RADNOR. — Garnet,  marmolite,  deweylite,  chromite,  asbestus,  magnesite,  talc,  blue  quartz, 
picrolite,  limonite,  magnetite. 

SPRINGFIELD. — Andalmite,  tourmaline,  beryl,  titanic  iron,  garnet;  on  Fell's  Laurel  Hill, 
beryl,  garnet ;  near  Beattie's  mill,  staurolite,  apatite ;  near  Lewis's  paper-mill,  tourmaline, 
mica. 

T  HO  RNBURY.  — Am  ethyst. 

HUNTINGDON  CO. — NEAR  FRANKSTOWN. — In  the  bed  of  a  stream  and  on  the  side  of  a 
hill,  fibrous  celestite  (abundant),  quartz  crystals. 

LANCASTER  CO. — DRUMORE  TOWNSHIP. — Quartz  crystals. 

FULTON.—  At  Wood's  chrome  mine,  near  the  village  of  Texas,  brucite  !  !  zaratite  (emerald 
nickel),  pennite  !  ripidolite!  kammererite!  baltimorite,  chromic  iron,  williamsite,  chrysolite! 
marmolite,  picrolite,  hydromagnesite,  dolomite,  magnesite,  aragonite,  calcite,  serpentine, 
hematite,  menaccanite,  genthite,  chrome-garnet,  bronzite,  millerite  ;  at  Low's  mine,  hydro- 
ma  gnesite,  brucite  (lancasterite),  picrolite,  magnesite,  williamsite,  chromic  iron,  ta'c,  zaratite, 
baltimorite,  serpentine,  hematite  ;  on  M.  Boice's  farm,  one  mile  N.W.  of  the  village,  pyrite 
in  cubes  and  various  modifications,  anthophyllite;  near  Rock  Springs,  chalcedony,  carnelian, 
mow  agate,  green  tourmaline  in  talc,  titanic  iron,  chromite,  octahedral  magnetite  in  chlonte  ; 
at  Reynoldo's  old  mine,  calcite,  talc,  picrolite,  chromite  ;  at  Carter's  chrome  mine,  brookite. 

GAP  MINES. — Chalcopyrite,  pyrrhotite  (niccoliferous),  millerite  in  botryoidal  radiations, 
mmanite  !  (rare),  actinolite,  siderite,  hisingerite,  pyrite. 

PEQUEA  VALLEY. — Eight  miles  south  of  Lancaster,  argentiferous  galenite  (said  to  contain 
250  to  300  ounces  of  silver  to  the  ton  ?),  vauquelinite,  rutile  at  Pequea  mine  ;  four  miles  N.W. 
of  Lancaster,  on  the  Lancaster  and  Harrisburg  Railroad,  calamite,  galenite,  blende  ;  pyrite  in 
cubic  crystals  is  found  in  great  abundance  near  the  city  of  Lancaster  ;  at  the  Lancaster  zinc 
mines,  calamine,  blende,  tennantite  ?  smithsonite  (pseud,  of  dolomite),  aurichalcite. 


AMERICAN   LOCALITIES.  463 

LEBANON"  CO.— CORNWALL. — Magnetite,  pyrite  (cobaltiferous),  chalcopyrite,  native  cop- 
per, azurite,  malachite,  chrysocolla,  cuprite  (hydrocuprite),  allophane,  brochantite,  serpentine, 
quartz  pseudomorphs ;  galenite  (with  octahedral  cleavage),  fluorite,  covellite,  hematite  (mi- 
caceous), opal,  asbestus. 

LEHIGH  CO. — FRTEDENSVILLE. — At  the  zinc  mines,  calamine,  smithsonite,  hydrozincite, 
massive  blende,  greenockite,  quartz,  allophane,  zinciferous  clay,  mountain  leather,  aragonite, 
sauconite  ;  near  Allentown,  magnetite,  pipe-iron  ore ;  near  Bethlehem,  on  S.  Mountain, 
alianite,  with  zircon  and  altered  sphene  in  a  single  isolated  mass  of  syenite,  magnetite,  mar- 
tite,  black  spinel,  tourmaline,  chalcocite. 

MIFFLIN  CO.— Strontianite. 

MONIIOE  CO. — In  CHERRY  VALLEY. — Calcite,  chalcedony,  quartz;  in  Poconac  Valley, 
near  Judge  Mervine's,  cryst.  quartz. 

MONTGOMERY  CO. — CONSHOHOCKEN. — Fibrous  tourmaline,  menaccanite,  aventurine 
quartz,  phyllite ;  in  the  quarry  of  Geo.  Bullock,  calcite  in  hexagonal  prisms,  aragonite. 

LOWER  PROVIDENCE. — At  the  Perkiomen  lead  and  copper  mines,  near  the  village  of 
Shannonville,  azurite,  blende,  galenite,  pyromorphite,  cernssite,  wulfenite,  anglesite,  barite, 
calamine,  chalcopyrite,  malachite,  chrysocolla,  brown  spar,  cuprite,  covellite  (rare),  mela- 
conite,  libethenite,  pseudomalachite. 

WifTTE  MARSH. — At  D.  O.  Hitner's  iron  mine,  five  and  a  half  miles  from  Spring  T\lills, 
limonite  in  geodes  and  stalactites,  gothite,  pyrolusite,  wad,  lepidocrocite  ;  at  Edge  Hill  Street, 
North  Pennsylvania  Railroad,  titanic  iron,  braunite,  pyrolusite;  one  mile  S.W.  of  Hitner's 
iron  mine,  limonite,  velvety,  stalactitic,  and  fibrous,  fibres  three  inches  long,  turgite,  gothite, 
pyrolusite,  velvet  manganese,,  wad ;  near  Marble  Hall,  at  Hitner's  marble  quarry,  white  mar- 
ble, granular  barite,  resembling  marble ;  at  Spring  Mills,  limonite,  pyrolusite,  gothite  ;  at 
Flat  Rock  Tunnel,  opposite  Manayunk,  stilbite,  heulandite,  chabasite,  ilvaite,  beryl,  feldspar, 
mica. 

LAFAYETTE,  at  the  Soapstone  quarries. — Talc,  jefferisite,  garnet,  albite,  serpentine,  zoisite, 
staurolite,  chalcopyrite  ;  at  Rose's  Serpentine  quarry,  opposite  Lafayette,  enstatite,  serpen- 
tine. 

NORTHUMBERLAND  CO.— Opposite  SELIM'S  GROVE.— Calamine. 

NORTHAMPTON  CO. — BUSHKILL  TOWNSHIP. — Crystal  Spring  on  Blue  Mountain,  quartz 
crystals. 

Near  EASTON. — Zircon!  (exhausted),  nephrite,  coccolite,  tremolite,  pyroxene,  sahlite, 
limonite,  magnetite,  purple  calcite. 

WILLIAMS  TOWNSHIP. — Pyrolusite  in  geodes  in  limonite  beds,  g5thite  (lepidocrocite)  at 
Glendon. 

PHILADELPHIA  CO. — FRANKFORD.— Titanite  in  gneiss,  apophyllite  ;  on  the  Philadelphia, 
Trenton  and  Connecting  Railroad,  basanite ;  at  the  quarries  on  Frankford  Creek,  stilbite, 
molybdenite,  hornblende  ;  on  the  Connecting  Railroad,  wad,  earthy  cobalt ;  at  Chestnut  Hill, 
magnetite,  green  mica,  chalcopyrite,  fluorite.  • 

FAIRMOUNT  WATER  WORKS. — In  the  quarries  opposite  Fairmount,  autunite!  torbernite, 
crystals  of  feldspar,  beryl,  pseudomorphs  after  beryl,  tourmaline,  albite,  wad,  menaccanite. 

GORGAS'  and  CREASE'S  Lane. — Tourmaline,  cyanite,  staurolite,  hornstone. 

Near  GERMANTOWN. — Black  tourmaline,  laumontite,  apatite;  York  Road,  tourmaline, 
beryl. 

HESTONVILLE. — Alunogen,  iron  alum,  orthoclase. 

HEFT'S  MILL. — Alunogen,  tourmaline,  cyanite,  titanite. 

MANAYUNK. — At  the  soapstone  quarries  above  Manayunk,  talc,  steatite,  chlorite,  vermicu- 
lite,  anthophyUite,  staurolite,  dolomite,  apatite,  asbestus,  brown  spar,  epsomite. 

MEAGARGEE'S  Paper-mill. — Staurolite,  titanic  iron,  hyalite,  apatite,  green  mica,  iron  gar- 
nets in  great  abundance. 

McKiNNEY's  Quarry,  on  Rittenhouse  Lane. — Feldspar,  apatite,  stilbite,  natrolite,  heulan- 
dite,  epidote,  hornblende,  erubescite,  malachite. 

SCHUYLKILL  FALLS. — Chabazite,  titanite,  fluorite,  epidote,  muscovite,  tourmaline,  pro- 
chlorite. 

SCHUYLKILL  CO.— TAMAQUA,  near  POTTSVILLE,  in  coal  mines.— KaoUnite. 
YORK  CO. — Bornite,  rutile  in  slender  prisms  in  granular  quartz,  calcite. 


464  APPENDIX. 


DELAWARE. 

NEWCASTLE  CO.— BRAND  YWINE  SPRINGS.—  BucJwlzite,  fibrolite  abundant,  sahlite,  pyrox- 
ene ;  Brandy  wine  Hundred,  muscovite,  enclosing  reticulated  magnetite. 

DIXON'S  FELDSPAR  QUARRIES,  six  miles  N.  W.  of  Wilmington  (these  quarries  have  been 
worked  for  the  manufacture  of  porcelain). — Adularia,  albite,  oligodase,  beryl,  apatite,  cinna- 
mon-stone! !  (both  granular  like  that  from  Ceylon,  and  crystallized,  rare),  magnesite,  serpen- 
tine, asbestus,  black  tourmaline!  (rare),  indicolite!  (rare),  sphene  in  pyroxene,  cyanite. 

DUPONT'S  POWDER  MILLS.— "  Hypersthene." 

EASTBURN'S  LIMESTONE  QUARRIES,  near  the  Pennsylvania  line. — Tremolite,  bronzite. 

QUARRYVILLE. — Garnet,  spodumene,  fibrolite. 

Near  NEWARK,  on  the  railroad. — Sphgerosiderite  on  drasy  quartz,  jasper  (ferruginous  opal), 
cryst.  spathic  iron  in  the  cavities  of  cellular  quartz. 

WAY'S  QUARKY,  two  miles  south  of  Centreville. — Feldspar  in  fine  cleavage  masses,  apatite, 
mica,  deweylite,  granular  quartz. 

WILMINGTON. — In  Christiana  quarries,  metaUoidal  diallage. 

KENNETT  TURNPIKE,  near  Centreville. — Cyanite  and  garnet. 

HARFORD  CO.— Cerolite. 

KENT  CO. — Near  MIDDLETOWN,  in  Wm.  Folk's  marl  pits. —  Vimanite  ! 
On  CHESAPEAKE  AND  DELAWARE  CANAL. — Retinasphalt,  pyrite,  amber. 

SUSSEX  CO. — Near  CAPE  HENLOPEN. — Vivianite. 

MARYLAND. 

BALTIMORE  (Jones's  Falls,  If  mile  from  B.). — Chabazite  (haydenite),  heulandite  (beau- 
montite  of  Levy),  pyrite,  lenticular  carbonate  of  iron,  mica,  stilbite. 

Sixteen  miles  from  Baltimore,  on  the  Gunpowder. — Graphite. 

Twenty-three  miles  from  B.,  on  the  Gunpowder. — Talc. 

Twenty-five  miles  from  B.,  on  the  Gunpowder. — Magnetite.  spJiene,  pycnite. 

Thirty  miles  from  B. ,  in  Montgomery  Co.,  on  farm  of  S.  Eliot. — Gold  in  quartz. 

Eight  to  twenty  miles  north  of  B. ,  in  limestone. — Tremolite,  augite,  pyrite,  brown  and  yel- 
low tourmaline. 

Fifteen  miles  north  of  B. — /Sky-blue  chalcedony  in  granular  limestone. 

Eighteen  miles  north  of  B.,  at  Scott's  mills. — Magnetite,  cyanite. 

BARE  HILLS. — Chr$mite.  asbestus,  tremolite,  talc,  hornblende,  serpentine,  chalcedony, 
meerschaum,  baltimorite,  cJialcopyrite,  magnetite. 

CAPE  SABLE,  near  Magothy  R. — Amber,  pyrite,  alum  slate. 

CARROLL  Co. — Near  Sykesville,  Liberty  Mines,  gold,  magnetite,  pyrite  (octahedrons),  cJial- 
copyrite, linnseite  (carrollite) ;  at  Patapsco  Mines,  near  Finksburg,  bornite,  malachite,  siegen- 
ite,  linnceite,  remingtonite,  magnetite,  chalcopyrite  ;  at  Mineral  Hill  mine,  bornite,  chalcopy- 
rite,  ore  of  nickel  (see  above),  gold,  magnetite. 

CECIL  Co.,  north  part. — Chromite  in  serpentine. 

COOPTOWN.  Harford  Co. — Olive-colored  tourmaline,  diallage,  talc  of  green,  blue,  and  rose 
colors,  ligniform  asbestus,  chromite,  serpentine. 

DEER  CREEK. — Magnetite!  in  chlorite  slate. 

FREDERICK  Co. — Old  Liberty  mine,  near  Liberty  Town,  black  copper,  malachite,  chalco- 
cite,  specular  iron ;  at  Dolly hyde  mine,  bornite,  chalcopyrite,  pyrite,  argentiferous  galenite  in 
dolomite. 

MONTGOMERY  Co.  —  Oxide  of  manganese. 

SOMERSET  and  WORCESTER  Cos.,  north  part.—  Bog-iron  ore,  mmanite. 

ST.  MARY'S  RIVER. — Gypsum!  in  clay. 

PYLESYILLE,  Harford  Co. — Asbestus  mine. 

VIRGINIA  AND  DISTRICT  OF  COLUMBIA. 

ALBEMARLE  Co.,  a  little  west  of  the  Green  Mts. — Steatite,  graphite,  galenite. 
AMHERST  Co.,  along  the  west  base  of  Buffalo  ridge. — Copper  ores,  allanite,  etc. 
AUGUSTA  Co. — At  Weyer's  (or  Weir's)  cave,  sixteen  miles  northeast  of  Staunton,  and 
eighty-one  miles  northwest  of  Richmond,  calcite,  stalactites. 


AMERICAN   LOCALITIES.  465 

BUCKINGHAM  Co.  —  Gold  at  Garnett  and  Moseley  mines,  also,  pyrite,  pyrrhotite,  calcite, 
garnet ;  at  Eldridge  mine  (now  London  and  Virginia  mines)  near  by,  and  the  Buckingham 
mines  near  Maysville,  gold,  auriferous  pyrite,  chalcopyrite,  tennantite,  barite  ;  cyanite,  tour- 
maline, actinolite. 

CHESTERFIELD  Co. — Near  this  and  Richmond  Co.,  bituminous  coal,  native  coke. 

CULPEPPER  Co.,  on  Rapidan  river. — Gold,  pyrite. 

FRANKLIN  Co. — Grayish  steatite. 

FAUQUIER  Co.,  Barnett's  mills. — Asbestus,  gold  mines,  barite,  calcite. 

FLUVANNA  Co. — Gold  at  Stockton's  mine  ;  also  tetradymite  at  u  Tellurium  mine." 

PHENJX  Copper  mines. — Chalcopyrite,  etc. 

GEORGETOWN,  D.  C. — Rutile. 

GOOCHLAND  Co.  — Gold  mines  (Moss  and  Busby's). 

HARPER'S  FERRY,  on  both  sides  of  the  Potomac. — Thuringite  (owenite)  with  quartz. 

JEFFERSON  Co.,  at  Shepherdstown. —Fluor. 

KENAWHA  Co. — At  Kenawha,  petroleum,  brine  springs,  cannel  coal. 

LOUDON  Co. — Tabular  quartz,  drase,  pyrite,  talc,  chlorite,  soapstone,  asbestus,  chromite, 
actinolite,  quartz  crystals  ;  micaceous  iron,  bornite,  malachite,  epidote,  near  Leesburg  (Poto- 
mac mine). 

LOUISA  Co. — Walton  gold  mine,  gold,  pyrite,  chalcopyrite,  argentiferous  galenite,  siderite. 
blende,  anglesite  ;  boulangerite,  blende  (at  Tinder's  mine). 

NELSON  Co. — Galeuite,  chalcopyrite,  malachite. 

ORANGE  Co. — Western  part,  Blue  Ridge,  specular  iron ;  gold  at  the  Orange  Grove  and 
Vaucluse  gold  mines,  worked  by  the  "  Freehold"  and  "Liberty"  Mining  Companies. 

ROCKBRIDGE  Co.,  three  miles  southwest  of  Lexington. — Barite. 

SHENANDOAH  Co.,  near  Woodstock. — Fluorite. 

MT.  ALTO,  Blue  Ridge. — Argillaceous  iron  ore. 

SPOTTSYLVANIA  Co.,  two  miles  northeast  of  Chancellorville.  —  Cyanite  ;  gold  mines  at  the 
junction  of  the  Rappahannock  and  Rapidan ;  on  the  Rappahannock  (Marshall  mine) ;  White- 
hall mine,  affording  also  tetradymite. 

STAFFORD  Co. ,  eight  or  ten  miles  from  Falmouth — Micaceous  iron,  gold,  tetradymite,  sil- 
ver, galenite,  vivianite. 

WASHINGTON  Co.,  eighteen  miles  from  Abington. — Rock  salt  with  gypsum. 

WYTHE  Co.  (Austin's  mines). —  Cerussite,  minium,  plumbic  ochre,  blende,  calamine,  galenite, 
graphite. 

On  the  Potomac,  twenty-five  miles  north  of  Washington  city. — Native  sulphur  in  gray 
compact  limestone. 

NORTH  CAROLINA. 

ASHE  Co. — Malachite,  chalcopyrite. 

BUNCOMBE  Co.,  (now  called  Madison  Co). — Corundum  (from  a  boulder),  margarite,  corun- 
dophilite,  garnet,  chromite,  barite,  fluorite,  rutile,  iron  ores,  manganese,  zircon;  at  Swan- 
nanoa  Gap,  cyanite. 

BURKE  Co. — Gold,  monazite,  zircon,  beryl,  corundum,  garnet,  sphene,  graphite,  iron  ores, 
tetradymite,  montanite. 

CABARRUS  Co. — Phenix  Mine,  gold,  barite,  chalcopyrite,  auriferous  pyrite,  quartz,  ps^udo- 
morph  after  barite,  tetradymite,  montanite  ;  Pioneer  mines,  gold,  limonite,  pyrolusite,  burn,- 
hardite,  wolfram,  scheelite,  cuprotungstite,  tungstite,  diamond,  chrysocolla,  chalcocite,  molyb- 
denite, chalcopyrite,  pyrite  ;  White  mine,  needle  ore,  chalcopyrite,  barite ;  Long  and  Muse's 
mine,  argentiferous  galenite,  pyrite,  chalcopyrite,  limonite  ;  Boger  mine,  tetradymite ;  Fink 
mine,  valuable  copper  ores  ;  Mt.  Makins,  tetrahedrite,  magnetite,  talc,  blende,  pyrite,  prous- 
tite,  galenite  ;  Bangle  mine,  scheelite. 

CALDWELL  Co. — Chromite. 

CHATHAM  Co. — Mineral  coal,  pyrite,  chloritoid. 

CHEROKEE  Co. — Iron  ores,  gold,  galenite,  corundum,  rutile,  cyanite,  damonite. 

CLEVELAND  Co. — White  Plains,  quartz,  crystals,  smoky  quartz,  tourmaline,  rutile  in  quartz. 

CLAY  Co. — At  the  Cullakenee  Mine  and  elsewhere,  corundum  (pink),  zoisite,  tourmaline, 
margarite,  willcoxite,  dudleyite. 

DAVIDSON  Co. — King's,  now  Washington  mine,  native,  silver,  cerussite,  anglesite,  scheelite. 
pyromorphite,  galenite,  blende,  malachite,  black  copper,  wavellite,  garnet,  stilbite  ;  five  miles 
from  Washington  mine,  on  Faust's  farm,  gold,  tetradymite,  oxide  of  bismuth  and  tellurium, 
montanite,  chalcopyribe,  limonite,  spathic  iron,  epidote ;  near  Squire  Ward's,  gold  in  crys- 
tals, electrum. 

FRANKLIN  Co. — At  Partiss  mine,  diamonds. 

GASTON  Co. — Iron  ores,  corundum,  margarite;    near  Crowder's  Mountain  (in  what  was 

30 


466  APPENDIX. 

formerly  Lincoln  Co.),  lazuli te,  cyanite,  garnet,  graphite  ;  also  twenty  miles  northeast,  near 
south  end  of  Clubb's  Mtn.,  lazulite,  cyanite,  talc,  rutile,  topaz,  pyrophyilite ;  King's  Moun- 
tain (or  Briggs)  Mine,  native  tellurium,  altaite,  tedradymite,  montanite. 

GUILFORD  Co. — McCulloch  copper  and  gold  mine,  twelve  miles  from  Greensboro',  gold, 
pyrite,  chalcopyrite  (worked  for  copper),  quartz,  siderite.  The  North  Carolina  Copper  Co.  are 
working  the  copper  ore  at  the  old  Fentress  mine ;  at  Deep  River,  compact  pyrophyilite 
(worked  for  slate-pencils). 

HAYWOOD  Co. — Corundum,  margarite,  damourite. 

HENDERSON  Co. — Zircon,  sphene  (xanthitane). 

JACKSON  Co. — Alunogen?  at  Smoky  Mt.;  at  Webster,  serpentine,  chromite,  genthite, 
chrysolite,  talc;  Hoghalt  Mt. ,  pink  corundum,  margarite,  tourmaline. 

LINCOLN  Co. — Diamond  ;  at  Randleman's.  amethyst,  rose  quartz. 

MACON  Co. — Franklin,  Culsagee  Mine,  corundum,  spinel,  diaspore,  tourmaline,  damourite, 
prochlorite,  culsageeite,  kerrite,  maconite. 

MCDOWELL  Co. — Brookite,  monazite,  corundum  in  small  crystals  red  and  white,  zircons, 
garnet,  beryl,  sphene,  xenotime,  rutile,  elastic  sandstone,  iron  ores,  pyromelane,  tetrady- 
mite,  montanite. 

MADISON  Co. — 20  miles  from  Asheville,  corundum,  margarite,  chlorite. 

MECKLENBURG  Co. — Near  Charlotte  (Rhea  and  Cathay  mines)  and  elsewhere,  chalcopyrite. 
gold;  chaleotrichite  at  McGinn's  mine;  barnhardtite  near  Charlotte;  pyrophyilite  in  Cot- 
ton Stone  Mountain,  diamond;  Flowe  mine,  scheelite,  wolframite;  T odd's  Branch,  mona- 
zite. 

MITCHELL  Co. — Samarskitc,  pyrochlore  (?),  euxenite,  columbite,  muscovite. 

MONTGOMERY  Co. — Steele's  mine,  ripidolite,  albite. 

MOORE  Co. — Carbonton,  compact  pyrophyilite. 

ROWAN  Co. — Gold  Hill  Mines,  thirty-eight  miles  northeast  of  Charlotte,  and  fourteen 
from  Salisbury,  gold,  auriferous  pyrite  ;  ten  miles  from  Salisbury,  feldspar  in  crystals,  bis- 
muthinite. 

RANDOLPH  Co. — Pyrophyilite. 

RUTHERFORD  Co.  — Gold,  graphite,  bismuthic  gold,  diamond,  euclase,  pseudomorphous 
quartz?,  chalcedony,  corundum  in  small  crystals,  epidote,  pyrope,  brookite,  zircon,  monazite, 
rutherfordite,  samarskite,  quartz  crystals,  itacolumyte ;  on  the  road  to  Cooper's  Gap, 
cyanite. 

STOKES  AND  SURRY  Cos. — Iron  ores,  graphite. 

UNION  Co. — Lemmond  gold  mine,  eighteen  miles  from  Concord  (at  Stewart's  and  Moore's 
mine),  gold,  quartz,  blende,  argentiferous  galenite  (containing  29-4  oz.  of  gold  and  86 -5  oz. 
of  silver  to  the  ton,  Genth),  pyrite,  some  chalcopyrite. 

YANCEY  Co. — Iron  ores,  amianthus,  chromite,  garnet  (spessartite),  samarskite. 

SOUTH  CAROLINA. 

ABBEVILLE. — DIST. — Oakland  Grove,  gold  (Dorn  mine),  galenite,  pyromorphite,  amethyst, 
garnet. 

ANDERSON  DIST. — At  Pendleton,  actinolite,  galenite,  kaolin,  tourmaline. 

CHARLESTON.  — Selenite. 

CHEOWEE  VALLEY.  —Galenite,  tourmaline,  gold. 

CHESTERFIELD  DIST.-— Gold  (Brewer's  mine),  talc,  chlorite,  pyrophyilite,  pyrite,  native 
bismuth,  carbonate  of  bismuth,  red  and  yellow  ochre,  whetstone,  enargite. 

DARLINGTON. — Kaolin . 

EDGEFTELD  DIST.— Psilomelane. 

GREENVILLE  DIST.— Galenite,  pyromorphite,  kaolin,  chalcedony  in  buhrstone,  beryl, 
plumbago,  epidote,  tourmaline. 

KERSIIAW  DIST. — Rutile. 

LANCASTER  DIST. — Gold  (Hale's  mine),  talc,  chlorite,  cyanite,  elastic  sandstone,  pyrite ; 
gold  also  at  Blackman's  mine,  Massey's  mine,  Ezell's  mine. 

LAURENT  DIST. — Corundum,  damourite. 

NEWBERRY  DIST. — Leadhillite. 

PICKEN'S  DIST. — Gold,  manganese  ores,  kaolin. 

HIGHLAND  DIST.  — Chiastolite,  novaculite. 

SPARTANBURG  DIST. — Magnetite,  chalcedony,  hfmatite ;  at  the  Cowpens,  limonite,  graphite, 
limestone,  copperas  ;  Morgan  mine,  leadhillite,  pyromorphite,  cerussite. 

SUMTER  DIST. — Agate. 

UNION  DIST. — Fairforest  gold  mines,  pyrite,  chalcopyrite. 

YORK  DIST. — Limestones,  whetstones,  witherite,  barite,  tetradymite. 


AMERICAN   LOCALITIES.  467 

GEORGIA. 

BURKE  AND  SCRHTEN  Cos. — Hyalite. 

CHEROKEE  Co. — At  Canton  Mine,  chalcopyrite,  galenite,  clausthalite,  plumbogummite, 
hitchcockite,  arsenopyrite,  lanthanite,  harrisite,  cantonite,  pyromorphite,  automolite,  zinc, 
staurolite,  cyanite  ;  at  Ball-Ground,  spodumene. 

CLARK  Co.,  near  Clarksville. — Gold,  xenotime,  zircon,  rutile,  cyanite,  hematite,  garnet, 
quartz. 

DADE  Co. — Halloysite,  near  Rising  Fawn. 

FANNIN  Co. — Staurolite  f  chalcopyrite. 

HABERSHAM  Co. — Gold,  py  \-ite,  chalcopyrite,  galenite,  hornblende,  garnet,  quartz,  kaolinite, 
soapstone,  chlorite,  rutile,  iron  ores,  tourmaline,  staurol'ite,  zircon. 

HALL  Co. — Gold,  quartz,  kaolin,  diamond. 

HANCOCK  Co. — Agate,  chalcedony. 

HEARD  Co. — Molybdite,  quartz. 

LINCOLN  Co. — Lazulite!  !  rutile! !  hematite,  cyanite.  menaccanite,  pyrophyllite,  gold, 
itacolmnyte  rock. 

LOWNS  Co. — Corundum. 

LUMPKIN  Co. — At  Field's  gold  mine,  near  Dahlonega,  gold,  tetradymite,  pyrrhotite,  chlorite, 
menaccanite,  allanite,  apatite. 

RABUN  Co. — Gold,  chalcopyrite. 

SPAULDING  Co. — Tetradymite. 

WASHINGTON  Co.,  near  Sauudersville. —  Wavellite,  fire  opal. 

ALABAMA. 

BIBB  Co.,  Centreville. — Iron  ores,  marble,  barite,  coal,  cobalt. 

TUSCALOOSA  Co.  —  Coal,  galenite,  pyrite,  vivianite,  limonite,  calcite,  dolomite,  cyanite, 
steatite,  quartz  crystals,  manganese  ores. 

BENTON  Co. — Antimonial  lead  ore  (boulangerite  ?) 

TALLAPOOSA  Co.,  at  Dudleyville. — Corundum,  spinel,  tourmaline. 

FLORIDA. 

NEAR  TAMPA  BAY. — Limestone,  sulphur  springs,  chalcedony,  carnelian,  agate,  silicified 
shells  and  corals. 

KENTUCKY. 

ANDERSON  Co. — Galenite,  barite. 
CLINTON  Co. — Geodes  of  quartz. 
CKITTENDEN  Co. — Galenite,  fluorite,  calcite. 

CUMBERLAND  Co. — At  mammoth  Gave,  gypsum  rosettes/  calcite,  stalactites,  nitre,  ep- 
somite. 

FAYETTE  Co. — Six  miles  N.E.  of  Lexington,  galenite,  barite,  witherite,  blende. 
LIVINGSTONE  Co.,  near  the  line  of  Union  Co. — Galenite,  chalcopyrite,  large  vein  of  fluorite. 
MERCER  Co. — At  McAfee,  Jluorile,  pyrite.  calcite,  barite,  celestite. 
OWEN  Co. — Galenite,  barite. 

TENNESSEE. 

BROWN'S  CREEK. — Galenite.  blende,  barite,  celestite. 

CARTER'S  Co.,  foot  of  Roan  I&t.—Saklite,  magnetite. 

CLAIBORNE  Co. — Calamine,  galenite,  smithsonite,  chlorite,  steatite,  magnetite. 

COCKE  Co.,  near  Brush  Creek. — Cacoxene  ?  kraurite,  iron  sinter,  stilpnosiderite,  brown 
hematite. 

DAVIDSON  Co. — Selenite,  with  granular  and  snowy  gypsum,  or  alabaster,  crystallized  and 
compact  anhydrite,  fluorite  in  crystals?  calcite  iii  crystals.  Near  Nashville,  blue  celestite, 
(crystallized,  fibrous,  and  radiated),  with  barite  in  limestone.  Haysboro',  galenite,  blende, 
with  barite  as  the  gangue  of  the  ore. 

DICKSON  Co.  — Manganite. 


468  APPENDIX. 

JEFFERSON  Co. — Calamine,  galenite,  fetid  barite. 

KNOX  Co. — Magnesian  limestone,  native  iron,  variegated  marbles  ! 

MA  DRY  Co. — Wavellite  in  limestone. 

MORGAN  Co. — Epsom  salt,  nitrate  of  lime. 

POLK  Co.,  Ducktown  mines,  southeast  corner  of  State. — Melaconite,  chalcopyrite,  pyrite, 
native  copper,  bornite,  rutile,  zoisite,  galenite,  harrisite,  alisonite,  blende,  pyroxene,  tremolite, 
sulphates  of  copper  and  iron  in  stalactites,  allophane,  rahtite,  chalcocite  (ducktownite),  chal- 
cotrichite,  azurite,  malachite,  pyrrhotite,  limonite. 

ROAN  Co.,  eastern  declivity  of  Cumberland  Mts. — Wavellite  in  limestone. 

SEVIER  Co.,  in  caverns. — Epsom  salt,  soda  alum,  saltpetre,  nitrate  of  lime,  breccia  marble. 

SMITH  Co. — Fluorite. 

SMOKY  MT.,  on  declivity. — Hornblende,  garnet,  staurolite. 

WHITE  Co. — Nitre. 

OHIO. 

BAINBRIDGE  (Copperas  Mt.,  a  few  miles  east  of  B,). — Calcite,  barite,  pyrite.  copperas, 
alum. 

CANFIELD. — Gypsum  ! 
DUCK  CREEK,  Monroe  Co. — Petroleum. 

LAKE  ERIE. — Strontian  Island,  celestite!  Put-in  Bay  Island,  celestite!  sulphur!  calcite. 
LIVERPOOL. — Petroleum. 

MARIETTA. — Argillaceous  iron  ore ;  iron  ore  abundant  also  in  Scioto  and  Lawrence  Cos. 
OTTAWA  Co. — Gypsum. 
POLAND. — Gypsum  ! 

MICHIGAN. 

BREST  (Monroe  Co.). — Calcite,  amethystine  quartz,  apatite,  celestite. 

GRAND  RAPIDS. — Selenite,  fib.  and  granular  gypsum,  calcite,  dolomite,  anhydrite. 

*LAKE  SUPERIOR  MINING  REGION. — The  four  principal  regions  are  Keweenaw  Point.  Isle 
Royale,  the  Ontonagon,  and  Portage  Lake.  The  mines  of  Keweenaw  Point  are  along  two 
ranges  of  elevation,  one  known  as  the  Greenstone  Range,  and  the  other  as  the  Southern  or 
Bohemian  Range  (Whitney) .  The  copper  occurs  in  the  trap  or  amygdaloid,  and  in  the  asso- 
ciated conglomerate.  Native  copper  !  native  silver  !  chalcopyrite,  horn  silver,  tetrahedrite, 
manganese  ores,  epidote,  prehnite,  laumontite,  datolite,  heulandite,  orthoclase,  ana1  cite,  cha- 
bazite,  compact  datolite,  chrysocolla,  mesotype  (Copper  Falls  mine),  leonhardite  (ib.),  analcite 
(ib.),  apophyllite  (at  Cliff  mine),  wollnstonite  (ib. ),  calcite,  quartz  (in  crystals  at  Minnesota 
mine),  compact  datolite,  orthoclase  (Superior  mine),  saponite,  melaconite  (near  Copper  Har- 
bor, but  exhausted),  chrysocolla  ;  on  Chocolate  River,  galenite  and  sulphide  of  copper ;  chal- 
copyrite and  native  copper  at  Presq'  Isle  ;  at  Albion  mine,  domeykite  ;  at  Prince  Vein,  barite, 
calcite,  amethyst ;  at  Michipi^,oten  Ids.,  copper  nickel,  stilbite,  analcite  ;  at  Albany  and  Bos- 
ton mine,  Portage  Lake,  prehnite,  analcite,  orthoclase,  cuprite ;  at  Sheldon  location,  domey- 
kite, whitneyite,  algodonite  ;  Isle  Royale  mine,  Portage  Lake,  compact  datolite  ;  Quincy  mine, 
calcite,  compact  datolite.  At  the  Spun*  Mountain  Iron  mine  (magnetite),  chlorite  pseudo- 
morph  after  garnet. 

MARQUETTE. — Manganite,  galenite;  twelve  miles  west  at  Jackson  Mt. .  and  other  mines, 
hematite,  limonite,  gothite  !  magnetite,  jasper. 

MONROE. — Aragonite,  apatite. 

POINT  AUX  PEAIJX  (Monroe  Co.). — Amethystine  quartz,  apatite,  celestite,  calcite. 

SAGINAW  BAY. — At  Alabaster,  gypsum. 

STONY  POINT  (Monroe  Co.). — Apatite,  amethystine  quartz,  celestite,  calcite. 

ILLINOIS. 

GALLATIN  Co.,  on  a  branch  of  Grand  Pierre  Creek,  sixteen  to  thirty  miles  from  Shawnee- 
town,  down  the  Ohio,  and  from  half  to  eight  miles  from  this  river. —  Violet  flaorite  !  in  car- 
boniferous limestone,  barite,  galenite,  blende,  brown  iron  ore. 

HANCOCK  Co. — At  Warsaw,  quartz  geodes  !  containing  calcite!  chalcedony,  dojomite,  Vende! 
brown  spar,  pyrite,  aragonite,  gypsum,  bitumen. 


*  See  also  Pumpelly  ;    on  the  Paragenesis  of  copper  ani  its  associate  minerals  on  Lake 
Superior.     Am.  J.  Sci.,  III.,  x,  17. 


AMERICAN   LOCALITIES.  469 

HARDIN  Co. — Near  Rosiclare,  calotte,  galenite,  blende  ;  five  miles  back  from  Elizabeth- 
town,  bog-iron  ;  one  mile  north  of  the  river,  between  Elizabeth  town  and  Rosiclare,  nitre. 

Jo  DAVIES  Co. — At  Galena,  galenite,  calcite,  pyrite,  blende;  at  Marsden's  diggings,  galen- 
ite  !  blende,  cerussite,  marcasite  in  stalactitic  forms,  pyrite. 

JOLIET.  — Marble. 

QUINCY. —  Calcite!  pyrite. 

SCALES  MOUND. — Barite,  pyrite. 

INDIANA. 

LIMESTONE  CAVERNS  ;  Corydon  Caves,  etc. — Epsom  salt. 

In  most  of  the  southwest  counties,  pyrile,  iron  sulphate,  and  feather  alum ;  on  Sugar 
Creek,  pyrite  and  iron  sulphate ;  in  sandstone  of  Lloyd  Co.,  near  the  Ohio,  gypsum  ;  at  the 
top  of  the  blue  limestone  formation,  brown  spar,  calcite. 

LAWRENCE  Co.— Spice  Valle,  kaolinite  (=indianaite). 

MINNESOTA. 

NORTH  SHORE  OF  L.  SUPERIOR)  range  of  hills  running  nearly  northeast  and  southwest, 
extending  from  Fond  du  Lac  Superieure  to  the  Kamanistiqueia  River  in  Upper  Canada). — 
Scolecite,  apophyllite,  prehnite,  stilbite,  lawnontite,  heulandite,  harmotome,  thomsonite,  fluorite, 
barite,  tourmaline,  epidote,  hornblende,  calcite,  quartz  crystals,  pyrite,  magnetite,  stea- 
tite, blende,  black  oxyd  of  copper,  malachite,  native  copper,  chalcopyrite,  amethystine 
quartz,  ferruginous  quartz,  chalcedony,  carnelian,  agate,  drusy  quartz,  hyalite?  fibrous  quartz, 
jasper,  prase  (in  the  debris  of  the  lake  shore),  dogtooth,  spar,  augite,  native  silver,  spodumene  ? 
chlorite ;  between  Pigeon  Point  and  Fond  du  Lac,  near  Baptism  River,  saponite  (thalite)  in 
amygdaloid. 

KETTLE  RIVER  TRAP  RANGE. — Epidote,  nail-head  calcite,  amethystine  quartz,  calcite, 
undetermined  zeolites,  saponite. 

STILL  WATER.  — Blende . 

FALLS  OP  THE  ST.  CROIX. — Malachite,  native  copper,  epidote,  nail-head  spar. 

RAINY  LAKE — Actinolite,  tremolite,  fibrous  hornblende,  garnet,  pyrite,  magnetite,  steatite. 

WISCONSIN. 

BIG  BULL  FALLS  (near). — Bog  iron. 

BLUE  MOUNDS. — Cerussite. 

HAZLE  GREEN. — Calcite. 

LAC  Du  FLAMBEAU  R. — Garnet,  cyanite. 

LEFT  HAND  R.  (near  small  tributary). — Malachite,  chalcocite,  native  copper,  red  copper 
ore,  earthy  malachite,  epidote,  chlorite  ?  quartz  crystals. 

LINDEN. —  Galenite,  smitlisonite,  hydrozincite. 

MINERAL  POINT  and  vicinity. — Copper  and  lead  ores,  chrysocolla,  azurite!  chalcopyrite, 
malachite,  galenite,  cerussite,  anglesite,  blende,  pyrite,  barite,  calcite,  marcasite,  smitJisonite  / 
(so-called  "dry-bone "). 

MONTREAL  RIVER  PORTAGE.— Galenite  in  gneissoid  granite. 

SANK  Co. — Hematite,  malachite,  chalcopyrite. 

SHULLSBURG. — Galenite/  blende,  pyrite  ;  at  Emmet's  digging,  galenite  and  pyrite. 

IOWA. 

Du  BUQUE  LEAD  MINES,  and  elsewhere. — Galenite  !  calcite,  blende,  black  oxide  of  man- 
ganese ;  at  Ewing's  and  Sherard's  diggings,  smitlisonite,  calamine ;  at  Des  Moines,  quartz 
crystals,  selenite  ;  Makoqueta  R. ,  brown  iron  ore  ;  near  Durango,  galenite. 

CEDAR  RIVER,  a  branch  of  the  Des  Moines. — tieknite  in  crystals,  in  the  bituminous  shale 
of  the  coal  measures  ;  also  elsewhere  on  the  Des  Moines,  gypsum  abundant ;  argillaceous 
iron  ore,  spathic  iron ;  copperas  in  crystals  on  the  Des  Moines,  above  the  Mouth  of  Saap 
and  elsewhere,  pyrite,  blende. 

FORT  DODGE. — Celestite. 

MAKOQUETA. — Hematite. 

NEW  GALENA. — Octahedral  galenite,  anglesite. 


470  APPENDIX. 

MISSOURI. 

BIRMINGHAM.  — Limonite. 

GRANBY.—  Sphalerite^  galenite,  calamine,  greenockite.  as  a  coating  on  sphalerite. 

JEFFERSON  Co.,  at  Valle's  diggings. — Galenite,  cerussite,  anglesite,  calamine,  chalcopy- 
rite  malachite,  azurite,  witherite. 

MINE  &  BURTON.  —  Galenite,  cerussite,  anglesite.  barite,  calcite. 

DEEP  DIGGINGS. — Malachite,  cerussite  in  crystals  and  manganese  ore. 

MADISON  Co. — Wolframite. 

MINE  LA  MOTTE.  —  Galenite!  malachite,  earthy  cobalt  and  nickel,  bog  manganese,  sulph- 
ide of  iron  and  nickel,  cerussite,  caledonite,  plumbogummite,  wolframite,  siegenite,  smaltite, 
aragonite. 

ST.  Louis. — Hitlerite,  calcite,  dolomite,  earthy  barite,  fluorite. 

ST.  FRANCIS  RIVER.  —Wolframite. 

PERRY'S  DIGGINGS,  and  elsewhere. — Galenite,  etc. 

Forty  miles  west  of  the  Mississippi  and  ninety  south  of  St.  Louis,  the  iron  mountains, 
specular  iron,  limonite  ;  10  m.  east  of  Ironton,  wolframite,  tungstite. 

ARKANSAS. 

BATESVILLE. — In  bed  of  White  R.,  some  miles  above  Batesville,  gold. 

GREEN  Co. — Near  Gainesville,  lignite. 

HOT  SPRINGS  Co. — At  Hot  Springs,  wavellite,  thuringite  ;  Magnet  Cove,  brookite!  schor- 
lomite,  elcpolite,  magnetite,  quartz,  green  coccoJite,  garnet,  apatite,  perofskite  (hydrotitanite), 
rutile,  ripidolite,  thomsonite  (ozarkite),  microcline,  segirite. 

INDEPENDENCE  Co. — Lafferay  Creek,  psilomelane. 

LAWRENCE  Co. — Hoppe,  Bath,  and  Koch  mines,  smithsonite,  dolomite,  galenite  ;  nitre. 

MARION  Co. — Wood's  mine,  smithsonite,  hydrozincite  (marionite),  galenite  ;  Poke  bayou, 
braunite? 

OUACIIITA  SPRINGS. — Quartz?  whetstones. 

PULASKI  Co. — Kellogg  mine,  10  m.  north  of  Little  Rock,  tetrahedrite,  tennantite,  nacrite, 
galenite,  blende,  quartz. 

CALIFORNIA. 

The  principal  gold  mines  of  California  are  in  Tulare,  Fresno,  Mariposa,  Tuolumne.  Cala- 
veras,  El  Dorado,  Placer,  Nevada,  Yuba,  Sierra.  Butte,  Plumas,  Shasta,  Siskiyou.  and  Del 
Norte  counties,  although  gold  is  found  in  almost  every  county  of  the  State.  The  gold  occurs 
in  quartz,  associated  with  sulphides  of  iron,  copper,  zinc,  and  lead;  in  Calaveras  and  Tuo- 
lomne  counties,  at  the  Mellones,  Stanislaus,  Golden  Rule,  and  Rawhide  mines,  associated 
with  tellurides  of  gold  and  silver  ;  it  is  also  largely  obtained  from  placer  diggings,  and  further 
it  is  found  in  beach  washings  in  Del  Norte  and  Klamath  counties. 

The  copper  mines  are  principally  at  or  near  Copperopolis,  in  Calveras  county  ;  near  Genesee 
Valley,  in  Plumas  county ;  near  Low  Divide,  in  Del  Norte  county  ;  on  the  north  fork  of 
Smith's  River  ;  at  Soledad,  in  Los  Angeles  county. 

The  mercury  mines  are  at  or  near  New  Almaden  and  North  Almaden,  in  Santa  Clara  county; 
at  New  Idria  and  San  Carlos,  Monterey  county ;  in  San  Luis  Obispo  county  ;  at  Pioneer 
mine,  and  other  localities  in  Lake  county ;  in  Santa  Barbara  county. 

ALPINE  Co. — Morning  Star  mine,  enargite,  stephanite,  polybasite,  barite,  quartz,  pyrite, 
tetrahedite. 

AMADOR  Co. — At  Volcano,  chalcedony,  hyalite. 

ALAMEDA  Co. — Diabolo  Range*,  magnesite. 

BUTTE  Co. — Cherokee  Flat,  diamond,  platinum,  iridosmine. 

CALAVERAS  Co. — Copperopolis,  chalcopyrite,  malachite,  azurite,  serpentine,  picrolite,  native 
copper,  near  Murphy's,  jasper,  opal ;  albite,  with  gold  and  pyrite  ;  Mellones  mine,  calaverite, 
petzite. 

OONTRA-COSTA  Co — San  Antonio,  chalcedony. 

DEL  NORTE  Co. — Crescent  City,  agate,  carnelian ;  Low  Divide,  chalcopyrite,  bornite, 
malachite  ;  on  the  coast,  iridosmine,  platinum. 

EL  DORADO  Co. — Pilot  Hill,  chalcopyrite  ;  near  Georgetown,   hessite,  from  placer  dig- 

fings ;  Roger's  Claim,   Hope  Valley,  grossular  garnet,   in  copper  ore ;  Coloma,   chromite ; 
panish  Dry  Diggings,  gold ;  Granite  Creek>  roscoelite,  gold. 


AMERICAN   LOCALITIES.  47  J 

FRESNO  Co. — Chowchillas,  andalusite. 

HUMBOLDT  Co. — Cryptomorphite. 

'-      IN^O  Co. — Ingo  district,  galenite,  cermsite,  anglesite,  barite,  atacamite,  calcite,  grossular 
garnet ! 

LAKE  Co. — Borax  Lake,  borax!  sassolite,  glauberite  ;  Pioneer  mine,  cinnabar,  native  mer- 
cury, selenide  of  mercury  ;  near  the  Geysers,  sulphur,  hyalite ;  Redington  mine,  metacinna- 
barite. 

Los  ANGELES  Co.  —Near  Santa  Anna  River,  anhydrite ;  Williams  Pass,  chalcedony ; 
Soledad  mines,  chalcopyrite,  garnet,  gypsum ;  Mountain  Meadows,  garnet,  in  conper  ore. 

MARIPOSA  Co.  —  Chalcopyrite,  itacolumyte  ;  Centreville,  cinnabar;  Pine  Tree  Mine,  tetra- 
hedrite  ;  Burns  Creek,  limonite  ;  Greyer  Gulch,  pyrophyllite  ;  La  Victoria  mine,  azurite  !  near 
Coulterville.  cinnabar,  gold. 

MONO  Co. — Partzite. 

MONTEREY  Co. — Alisal  Mine,  arsenic  ;  near  Paneches,  chalcedony  ;  New  Idria  mine,  cin- 
nabar;  near  New  Idria,  chromite,  zaratite,  chrome  garnet;  near  Pacheco's  Paes,  stibnite. 

NEVADA  Co. — Grass  Valley  gold!  in  quartz  veins,  with  pyrite,  chalcopyrite,  blende, 
ars^nopyrite,  galenite,  quartz,  biotite  ;  near  Truckee  Pass,  gypsum ;  Excelsior  Mine,  molyb- 
denite, with  molybdenite  and  gold  ;  Sweet  Land,  pyrolusite. 

PLACER  Co.— Miner's  Ravine,  epidote  !  with  quartz,  gold. 

PLUM  AS  Co. — Genesee  Valley,  chalcopyrite  ;  Hope  mines,  bornite,  sulphur. 

SANTA  BARBARA  Co. — San  Amedio  Canon,  stibnite,  asphaltum,  bitumen,  maltha,  petro- 
leum, cinnabar,  iodide  of  mercury  ;  Santa  Clara  River,  sulphur. 

SAN  DIEGO  Co. — Carisso  Creek,  gypsum  ;  San  Isabel,  tourmaline,  orthoclase,  garnet. 

SAN  FRANCISCO  Co. — Red  Island,  pyrolusite  and  manganese  ores. 

SANTA  CLARA  Co. — New  Almaden,  cinnabar,  calcite,  aragonite,  serpentine,  chrysolite, 
quartz,  aragotite ;  North  Almaden,  chromite ;  Mt.  Diabolo  Range,  magnesite,  datolite,  with 
vesuvianite  and  garnet. 
fSAN  Luis  OBISPO  Co. — Asphaltum,  cinnabar,  native  mercury. 

SAN  BERNARDINO  Co. — Colorado  River,  agate,  trona ;  Temescal,  cassiterite  ;  Russ  Dis- 
trict, galenite,  cerussite  ;  Francis  mine,  cerargyrite. 

SHASTA  Co. — Near  Shasta  City,  hematite,  in  large  masses. 

SISKIYOU  Co. — Surprise  Valley,  selenite,  in  large  slabs. 

SONOMA  Co. — Actiuolite,  garnets. 

TULARE  Co. — Near  Visalia,  magnesite,  asphaltum. 

TUOLUMNE  Co.  — Tourmaline,  tremolite ;  Sonora,  graphite;  York  Tent,  chromite;  Golden 
Rule  mine,  petzite,  calaverite,  altaite,  hessite,  magnesite,  tetrahedrite,  gold  ;  Whiskey  Hill, 
gold  ! 

TRINITY  Co. — Cassiterite,  a  single  specimen  found. 

LOWER  CALIFORNIA. 
LA  PAZ. — Cuproscheelite.     LORETTO. — Natrolite,  siderite,  selenite. 

UTAH. 

BEAVER  Co — Bismuthinite,  bismite,  bismutite. 

TINTIC  DISTRICT. — At  the  Shoebridge  mine,  the  Dragon  mine,  and  the  Mammoth  vein, 
enargite  with  pyrite. 

Box  ELDER  Co.— Empire  mine,  wulfenite! 

In  the  Wahsatch  and  Oquirrh  mountains  there  are  extensive  mines,  especially  of  ores  of 
lead  rich  in  silver.  At  the  Emma  mine  occur  galeuite,  cervantite,  cerussite,  wulfenite, 
azurite,  malachite,  catamine,  anglesite,  linarite,  sphalerite,  pyrite,  argentite,  stephanite, 
etc.  At  the  Lucky  Boy  mine,  Butterfield  Canon.,  orpiment,  realgar. 

One  hundred  and  twenty  miles  south-west  of  Salt  Lake  City,  topaz  has  been  found  in  color- 
less crystals. 

NEVADA. 

CARSON  VALLEY.— Chrysolite. 

CHURCHILL  Co. — Near  Ragtown,  gay-luss»te,  trona,  common  salt. 

COMSTOCK  LODE. — Gold,  native  silver,  argentite,  stephanite,  polybasite,  pyrargyrite,  prous- 
tite,  tetrahedrite,  cerargyrite,  pyrite,  chalcopyrite,  galenite,  blende,  pyroinorphite,  allemon- 
tite,  arsenolite,  quartz,  calcite,  gypsum,  cerussite,  cuprite,  wulfenite,  amethyst,  kiistelite. 


472  APPENDIX. 

ESMERALDA  Co. — Alum,  12  m.  north  of  Silver  Creek  ;  at  Aurora,  fluorite,  stibnite  ;  near 
Mono  Lake,  native  copper  and  cuprite,  obsidian  ;  Columbus  district,  ulexite  ;  Walker  Lake, 
gypsum,  hematite  ;  Silver  Peak,  salt,  saltpetre,  sulphur,  silver  ores. 

HUMBOLDT  DISTRICT. — Sheba  mine,  native  silver,  jamesonite,  stibnite,  tetrahedrite,  prous- 
tite,  blende,  cerussite,  calcite,  bournonite,  pyrite,  galenite,  malachite,  xanthocone  (V) 

MAMMOTH  DISTRICT. — Orthoclase,  turquois,  hubnerite,  scheelite. 

REESE  RIVER  DISTRICT. — Native  silver,  proustite,  pyrargyrite,  stephanite,  blende,  poly- 
basite,  rhodochrosite,  embolite,  tetrahedrite  !  cerargyrite,  embolite. 

SAN  ANTONIA. — Belmont  mine,  stetefeldtite. 

Six  MILE  CAXON. — tidenite. 

ORMSBY  Co. — W.  of  Carson,  epidote. 

STOREY  Co. — Alum,  natrolite,  scolezite. 

ARIZONA. 

On  and  near  the  Colorado,  gold,  silver,  and  copper  mines;  at  Bill  Williams'  Fork,  chry- 
socolla.  malachite,  atacamite,  brochantite ;  Dayton  Lode,  gold,  fluorite,  cerargyrite  ;  Skinner 
Lode,  octahedral  fluorite ;  at  various  places  in  the  southern  part  of  the  territoiy,  silver  and 
copper  mines  ;  Heintzehnann  mine,  stromeyerite,  chalcocite,  tetrahedrite,  atacamite.  Mont- 
gomery mine,  Harsayampa  Dist. ,  tetradymite.  Whitneyite,  in  Southern  Arizona. 


OREGON. 

Gold  is  obtained  from  beach  washings  on  the  southern  coast ;  quartz  mines  and  placer 
mines  in  the  Josephine  district ;  also  on  the  Powder,  Burnt,  and  John  Day's  rivers,  and  other 
places  in  eastern  Oregon ;  platinum,  iridosmine,  laurite,  on  the  Rogue  River,  at  Port  Oxford, 
and  Cape  Blanco.  In  Curry  Co. ,  priceite. 

IDAHO. 

In  the  Owyhee,  Boise,  and  Flint  districts,  gold,  also  extensive  silver  mines ;  Poor  Man  Lode, 
cerargyitef  proustite,  pyrargyrite!  native  si?ver,  gold,  pyromorphite,  quartz,  malachite; 
polybasite;  on  Jordan  Creek,  stream  tin;  Rising  Star  mine,  stephanite,  aigentite,  pyrargy- 
rite. 

MONTANA. 

Many  mines  of  gold,  etc.,  west  of  the  Missouri  R.  HIGHLAND  DISTRICT. — Tetradymite. 
SILVER  STAR  DIST. — Psittacinite. 

In  the  Yellowstone  Park,  in  Montana  and  Wyoming  Territories.  —  Geyserite. — Amethyst! 
chalcedony,  quartz  crystals,  quartz  on  calcite,  etc. 


COLORADO.* 

The  principal  gold  mines  of  Colorado  are  in  Boulder,  Gilpin,  Clear  Creek,  and  Jefferson 
Cos.,  on  a  line  of  country  a  few  miles  W.  of  Denver,  extending  from  Long's  Peak  to  Pike's 
Peak.  A  large  portion  of  the  gold  is  associated  with  veins  of  pyrite  and  chal  copy  rite  ;  silver 
and  lead  mines  are  at  and  near  Georgetown,  Clear  Creek  Co.,  and  to  the  westward  in  Sum- 
mit Co.,  on  Snake  and  Swan  rivers. 

At  the  GEORGETOWN  mines  are  found  :— native  silver,  pyrargyrite,  argentite,  tetrahedrite, 
pyromorphite,  galenite,  sphalerite,  azurite,  aragonite,  barite,  fluorite,  mica. 

TRAIL  CREEK. — Garnet,  epidote,  hornblende,  chlorite;  at  the  Freeland  Lode,  tetrahedrite, 
tennantite,  anglesite.  caledonite,  cerussite,  tenorite,  siderite,  azurite,  minium  ;  at  the  Cham- 
pion Lode,  tenorite,  azurite,  chrysocolla,  malachite;  at  the  Gold  Belt  Lode,  vivianite;  at 
the  Kelly  Lode,  tenorite ;  at  the  Coyote  Lode,  malachite,  cyanotrichite. 

Near  BLACK  HAWK. — At  Willis  Gulch,  enargite,  fluorite,  pyrite  ;  at  the  Gilpin  County 
Lode,  cerargyrite  ;  on  Gregory  Hill,  feldspar;  North  Clear  Creek,  lievrite.  —  Galenite ! 

*  See  the  Catalogue  of  Minerals  of  Colorado  by  J.  Alden  Smith. 


AMERICAN   LOCALITIES.  473 

BEAR  CREEK. — Fluorite,  beryl;  near  the  Malachite  Lode.  maSacMte,  cuprite,  vesuvianite, 
topazolite  ;  Liberty  Lode,  chalcocite. 

SNAKE  RIVER. — Perm  District,  embolite ;  at  several  lodes,  pyrargyrite,  native  silver, 
azurite. 

RUSSELL  DISTRICT. — Delaware  Lode,  chalcopyrite,  crystallized  galenite. — Epidote,  pyrite. 

VIRGINIA  CAXON. — Epidote,  fluorite  ;  at  the  Crystal  Lode,  native  silver,  spinel. 

SUGAR  LOAF  DISTRICT. — Chalcocite,  pyrrhotite,  garnet  (manganesian). 

CENTRAL  CITY. — Garnet,  tenorite  ;  at  Leavitt  Lode,  molybdenite;  on  Gunnell  Hill,  mag- 
netite ;  at  the  Pleasantview  mine,  cerussite. 

GOLDEN  CITY. — Aragonite  ;  on  Table  Mountain,  leucite  in  amygdaloid. 

BERGEN'S  RANCHE. — Garnet,  actinolite,  calcite. 

BOULDER  Co.,  Red  Cloud  Mine. — Native  tellurium,  altaite,  hessite  (petzite),  sylvanite, 
calaverite,  schirrnerite. 

LAKE  CITY,  at  the  Hotchkiss  Lode. — Petzite,  calaverite  (?),  etc. 

PIKE'S  PEAK,  on  Elk  Creek. — Amazomtone  !  !  smoky  quartz!  aventurine  feldspar,  ame- 
thyst, albite,  fluorite,  hematite,  anhydrite  (rare),  columbite. 

CANADA. 

CANADA  EAST. 

ABERCROMBIE.  —  Labradorite. 

BAY  ST.  PAUL.—Mennaccanitef  apatite,  allanite,  rutile  (or  brookite  ?) 

AUBERT.  —  Gold,  iridosmine,  platinum. 

BOLTON.  —  Chromite,  magnesite,  serpentine,  picrolite,  steatite,  bitter  spar,  wad. 

BOUCIIERVILLE. — Auyite  in  trap. 

BROME. — Magnetite,  chalcopyrite,  sphene,  menaccanite,  phyllite,  sodalite,  cancrinite, 
galenite,  chloritoid. 

CIIAMBLY.— Anal  cite,  chabazite  and  calcite  in  trachyte,  menaccanite. 

CHATEAU  RICHER.—  Labradorite,  hypersthene,  andesite. 

DAILLEBOUT. — Blue  spinel  with  clintonite. 

GRENVILLE. — Wollastonite,  sphene,  vesuvianite,  calcite,  pyroxene,  steatite  (rensselaerite), 
garnet  (cinnamon-stone),  zircon,  graphite,  scapolite. 

HAM. — Chromite  in  serpentine,  diallage,  antimony!  senarmontite !  kermesite,  valentinite, 
stibnite. 

INVERNESS. — Variegated  copper. 

LAKE  ST.  FRANCIS. — Andalasite  in  mica  slate. 

LANDSDOWN.  — Barite. 

LEEDS. — Dolomite,  chalcopyrite,  gold,  chloritoid. 

MILLE  ISLES. — Labradorite  !  menaccanite,  hypersthene,  andesite,  zircon. 

MONTREAL.  —  Calcite,  augite,  sphene  in  trap,  chrysolite,  natrolite,  dawsonite. 

MORIN. — Sphene,  apatite,  labradorite. 

ORPORD. — White  garnet,  chrome  garnet,  millerite,  serpentine. 

OTTAWA. — Pyroxene. 

POLTON. — Chromite,  steatite,  serpentine,  amianthus. 

ROUGEMONT. — Augite  in  trap. 

SIIERBROOK. — At  Sum"  eld  mine,  albite  !  native  silver \  argentite,  chalcopyrite,  blende. 

ST.  ARMAND. — Micaceous  iron  ore  with  quartz,  epidote. 

ST.  FRANQOIS  BEAUCE.— Gold,  platinum,  iridosmine,  menaccanite,  magnetite,  serpentine, 
chromite,  soapstone,  barite. 

ST.  JEROME. — Sphene.  apatite,  chondrodite,  phlogopite,  tourmaline,  zircon,  molybdenite, 
pyrrhotite. 

ST.  NORBERT. — Amethyst  in  greenstone. 

STUKELEY. — Serpentine,  verd-antique  !  schiller  spar. 

SUTTON. — Magnetite  in  fine  crystals,  hematite,  rutile,  dolomite,  magnesite,  chromiferous 
talc,  bitter  spar,  steatite. 

UPTON. — Chalcopyrite,  malachite,  calcite. 

VAUDREUIL. — Limonite,  vivianite. 

YA.MASKA.— Sphene  in  trap. 

CANADA  WEST. 

ARNPRIOR.  — Calcite. 

BALSAM  LAKE. — Molybdenite,  scapolite,  quartz,  pyroxene,  pyrite. 
BRANTFORD. — Sulphuric  acid  spring  (4*2  parts  of  pure  sulphuric  acid  in  1000). 
BATHURST. — Barite,  black  tourmaline,  pcrthite  (orthoclase),  perifttcrite  (albite),  bytownite, 
pyroxene,  wilsonite,  scapolite,  apatite,  titanite. 


474:  APPENDIX. 

BROCKVILLE. — Pyrite. 

BIIOME. — Magnetite. 

BRUCE  MINES. — Calcite,  dolomite,  quartz,  chalcopyrite. 

BURGESS. — Pyroxene,  albite,  mica,  sapphire,  sphene,  chalcopyrite,  apatite,  black  spinel! 
spodumene  un  a  boulder),  serpentine,  biotite. 

BYTOWN. — Calcite,  bytownite,  chondrodite,  spinel. 

CAPE  IPPERWASH,  Lake  Huron. — Oxalite  in  shales. 

CLARENDON. —  Vesuvianite. 

DALHOUSIE.— Hornblende,  dolomite. 

DRUMMUND.  — Labradorite. 

ELIZABETHTOWN.—  Pyrrhotite,  pyrite,  calcite,  magnetite,  talc,  phlogopite,  siderite,  apa- 
tite, cacoxenite. 

ELMSEY. — Pyroxene,  sphene,  feldspar,  tourmaline,  apatite,  biotite,  zircon,  red  spinel, 
chondrodite. 

FITZROY. — Amber,  brown  tourmaline,  in  quartz. 

GCETINEAU  RIVER,  Blasdell's  Mills. — Calcite,  apatite,  tourmaline,  hornblende,  pyroxene. 

GRAND  CALUMET  ISLAND. — Apatite,  phlogopite  !  pyroxene  !  sphene,  vesumanite  !  !  serpen- 
tine, tremolite,  ftcapolite,  brown  and  black  tourmaline  !  pyrite,  loganite. 

HIGH  FALLS  OP  THE  MADAWASKA. — Pyroxene!  hornblende. 

HULL. — Magnetite,  garnet,  graphite. 

HUNTERSTOWN. — ScapoKte,  sphene,  vesuvianite,  garnet,  brown  tourmaline! 

H  UNTINGTON. — CaJcite  ! 

INNISKILLEN.  — Petroleum. 

KINGSTON. — Celestite. 

LAC  DES  CHATS,  Island  Portage. — Brown  tourmaline!  pyrite,  calcite,  quartz. 

LANARK. — Raphilite  (hornblende),  serpentine,  asbestus. 

LANDSTOWN. — Barite!  vein  27  in.  wide,  and  fine  crystals. 

MADOC.  — Magnetite. 

MAMORA. — Magnetite,  chalcolite,  garnet,  epsomite,  specular  iron. 

MAIM  ANSE.  — Pitchblende  (coracite) . 

McNAB. — Hematite,  barite. 

MICIIIPICOTEN  ISLAND,  Lake  Superior. — Domeykite,  niccolite,  genthite. 

NE WBORO  UGH.  —  Chondrodite,  graphite. 

PACKENIIAM.  -^Hornblende. 

PERTH. — Apatite  in  large  beds,  phlogopite. 

SOUTH  CROSBY. —Chondrodite  in  limestone,  magnetite. 

ST.  ADKLE. — Chondrodite  in  limestone. 

ST.  IGNACE  ISLAND. — Calcite,  native  copper. 

SYDENHAM. — Celestite. 

TERRACE  COVE,  Lake  Superior. — Molybdenite. 

WALLACE  MINE,  Lake  Huron. — Hematite,  nickel  ore,  nickel  vitriol. 

NEW  BRUNSWICK.* 

ALBERT  Co, — Hopewell,  gypsum  ;  Albert  mines,  coal  (albertite) ;  Shepody  Mountain, 
alunite  in  clay,  calcite,  iron  pyrites,  manganite,  psilomelane,  pyrolusite. 

CARLETON  Co. — Woodstock,  chalcopyrite,  hematite,  limonite,  wad. 

CHARLOTTE  Co.  —  Campobello,  at  Welchpool,  blende,  chalcopyrite,  bornite,  galenite, 
pyrite;  at  head  of  Harbor  de  Lute,  galenite  ;  Deer  Island,  on  west  side,  calcite,  magnetite, 
quartz  crystals;  Digdignash  River  on  west  side  of  entrance,  calcite!  (in  conglomerate1!, 
chalcedony  ;  at  Rolling  Dam,  graphite  ;  G-randmanan,  between  Northern  Head  and  Dark 
Harbor,  agate,  amethyst,  apofihyllite,  calcite,  hematite,  heulandite,  jasper,  magnetite,  natro- 
lite,  siilbite ;  at  Whale  Cove,  calcite  !  heulandite,  laumontite.  stilbite,  semi-opal !  Wagagua- 
davic  River,  at  entrance,  azurite,  chalcopyrite  in  veins,  malachite. 

GLOUCESTER  Co. — Tete-a-Gouche  River,  eight  miles  from  Bathurst,  chalcopyrite  (mined), 
oxide  of  manganese!  !  formerly  mined.  - 

KINGS  Co. — Sussex,  near  Gloat's  mills,  on  road  to  Belleisle,  argentiferous  galenite  ;  one 
mile  north  of  Baxter's  Inn,  specular  iron  in  crystals,  limonite ;  on  Capt.  McCready's  farm, 
selenite  !  ! 

RESTIGOUCHE  Co. — Belledune  Point,  calcite!  serpentine,  verd-antique  ;  Dalhousie,  agate, 
carnelian. 

*  For  a  more  complete  list  of  localities  in  New  Brunswick,  Nova  Scotia,  and  Newfound- 
land, see  catalogue  by  0.  C.  Marsh,  Am.  J.  Sci.,  II.  xxxv.  210,  1863. 


AMERICAN   LOCALITIES.  475 

SAINT  JOHN  Co. — Black  Kiver,  on  coast,  calcite,  chlorite,  chalcopyrite,  hematite!  Brandy 
Brook,  epidote,  hornblende,  quartz  crystals  ;  Carleton,  near  Falls,  calcite  ;  Chance  Harbor, 
calcite  in  quartz  veins,  chlorite  in  argillaceous  and  talcose  slate;  Little  Dipper  Harbor,  on 
west  side,  in  greenstone,  amethyst,  barite,  quartz  crystals  ;  Moosepath,  feldspar,  hornblende, 
muscovite,  black  tourmaline  ;  Musquash,  on  east  side  harbor,  copperas,  graphite,  pyrite  ;  at 
Shannon's,  chrysolite,  serpentine  ;  east  side  of  Musquash,  quartz  crystal !  ;  Portland,  at 
the  Falls,  graphite ;  at  Fort  Howe  Hill,  calcite,  graphite  ;  Crow's  Nest,  asbestus,  chryso'ite, 
magnetite,  serpentine,  steatite;  Lily  Lake,  white  augite  ?  chrysolite,  graphite,  serpentine, 
steatite,  talc;  How's  Road,  two  miles  out,  epidote  (in  syenite),  steatite  in  limestone,  tremo- 
lite;  Drury's  Cove,  graphite,  pyrite,  pyrallolite  ?  indurated  talc  ;  Quaco,  at  Lighthouse  Point, 
large  bed  oxyd  of  manganese ;  Sheldon's  Point,  actinolite,  asbestus,  calcite,  epidote,  mala- 
chite, specular  iron  ;  Cape  Spenser,  asbestus,  calcite,  chlorite,  specular  iron  (in  crystals  ; 
Westbeach,  at  east  end,  on  Evans'  farm,  chlorite,  talc,  quartz  crystals  ;  half  a  mile  west, 
chlorite,  chalcopyrite,  magnesite  (vein),  magnetite  ;  Point  Wolf  and  Salmon  River,  asbestus, 
chlorite,  chrysocolla,  chalcopyrite,  bornite,  pyrite. 

VICTORIA  Co. — Tabique  River,  agate,  carne'ian,  jasper;  at  mouth,  south  side,  galenite  ; 
at  mouth  of  Wapskanegan,  gypsum,  salt  spring  ;  three  miles  above,  stalactites  (abundant) ; 
Quisabis  River,  blue  phosphate  of  iron,  in  clay. 

WESTMORELAND  Co.  — Bellevue,  pyrite ;  Dorcester,  on  Taylor's  farm,  cannel  coal ;  clay 
ironstone  ;  on  Ayres's  farm,  asphaltum,  petroleum  spring  ;  Grandlance,  apatite,  selenite  (in 
large  crystals);  Memramcook,  coal  (albertite) ;  Shediac,  four  miles  up  Scadoue  River,  coal. 

YORK  Co. — Near  Fredericton,  stibnite,  jamesonite,  berthierite  ;  Pokiock  River,  stibnite, 
tin  pyrites?  in  granite  (rare). 

NOVA  SCOTIA. 

ANNAPOLIS  Co.— Chute's  Cove,  apoyhyllite,  natrolite;  Gates'  Mountain,  analcite,  magne- 
tite, mesolite!  natrolite,  stilbite  ;  Martial's  Cove,  analcite!  chabazite,  heulandite;  Moose 
River,  beds  of  magnetite ;  Nictau  River,  at  the  Falls,  bed  of  hematite  ;  Paradise  River,  black 
tourmaline,  smoky  quartz  !  !  ;  Port  George,  faroelite,  laumontite,  mesolite,  stilbite  ;  east  of 
Port  George,  on  coast,  apophyllite  containing  gyrolite  ;  Peter's  Point,  west  side  of  Stonock's 
Brook,  apophyllite  !  calcite,  heulandite,  laumontite  !  (abundant),  native  copper,  stilbite  ;  St. 
Croix  Cove,  chabazite,  heulandite. 

COLCHESTER  Co. — Five  Islands,  East  River,  barite!  calcite,  dolomite  (ankerite),  hematite, 
chalcopyrite  ;  Indian  Point,  malachite,  magnetite,  red  copper,  tetrahedrite  ;  Pinnacle  Islands, 
analcite,  calcite,  chabazite !  natrolite,  siliceous  sinter ;  Londonderry,  on  branch  of  Great 
Village  River,  barite,  ankerite,  hematite,  limonite,  magnetite;  Cook's  Brook,  ankerite,  hema- 
tite ;  Martin's  Brook,  hematite,  limonite ;  at  Folly  River,  below  Falls,  ankerite,  pyrite  ;  on 
high  land,  east  of  river,  ankerite,  hematite,  limonite ;  on  Archibald's  land,  ankerite,  barite, 
hematite ;  Salmon  River,  south  branch  of,  chalcopyrite,  hematite ;  Shubenacadie  River, 
anhydrite,  calcite,  barite,  hematite,  oxide  of  manganese;  at  the  Canal,  pyrite;  Stewiaoke 
River,  barite  (in  limestone). 

CUMBERLAND  Co. — Cape  Chiegnecto,  barite;  Cape  D'Or,  analcite,  apophyllite!  !  chaba- 
zite, faroelite,  laumontite,  mesolite,  malachite,  natrolite,  native  copper,  obsidian,  red  copper 
(rare),  vivianite  (rare) ;  Horse- shoe  Cove,  east  side  of  Cape  D'Or,  analcite,  calcite,  stilbite  ; 
Isle  Haute,  south  side,  analcite,  apophyllite !  !  calcite,  heulandite  !  !  natrolite,  mesolite,  stil- 
bite !  Joggins,  coal,  hematite,  limonite ;  malachite  and  tetrahedrite  at  Seaman's  Brook  ; 
Partridge  Island,  analcite,  apophyllite!  (rare),  amethyst!  agate,  apatite  (rare),  calcite! ! 
chabazite  (acadialite),  chalcedony,  cat's-eye  (rare),  gypsum,  hematite,  heulandite!  magne- 
tite, atilbite  !  !  ;  Swan's  Creek,  west  side,  near  the  Point,  calcite,  gypsum,  heulandite,  pyrite  ; 
east  side,  at  Wasson's  Bluff  and  vicinity,  analcite!  !  apophyllite!  (rare),  calcite,  chabazite  f  f 
(acadialite),  gypsum,  heulandite! !  natrolite!  siliceous  sinter;  Two  Islands,  moss  agate, 
analcite,  calcite,  chabazite,  heulandite  ;  McKay's  Head,  analcite,  calcite,  heulandite,  siliceous 
sinter  ! 

DIGBY  Co.— Brier  Island,  native  copper,  in  trap;  Digby  Neck,  Sandy  Cove  and  vicinity, 
agate,  amethyst,  calcite,  chabazite,  hematite !  laumontite  (abundant),  magnetite,  stttbite, 
quartz  crystals ;  Gulliver's  Hole,  magnetite,  stilbite ! ;  Mink  Cove,  amethyst,  chabazite  I 
quartz  crystals;  Nichols  Mountain,  south  side,  amethyst,  magmtite  !  ;  Williams  Brook, 
near  source,  chabazite  (green),  heulandite,  stilbite,  quartz  crystal. 

GUYSBORO'  Co. — Cape  Canseau,  andalusite. 

HALIFAX  Co. — Gay's  river,  galenite  in  limestone ;  southwest  of  Halifax,  garnet,  staurolite, 
tourmaline  :  Tangier,  gold !  in  quartz  veins  in  clay  slate,  associated  with  auriferous  pyrites, 
galenite,  hematite,  mispickel,  and  magnetite ;  gold  has  also  been  found  in  the  same  forma- 
tion, at  Country  Harbor,  Fort  Clarence,  Isaac's  Harbor,  Indian  Harbor,  Laidlow's  farm, 
Lawrencetown,  Sherbrooke,  Salmon  River,  Wine  Cove,  and  other  places. 


476  APPENDIX. 

HANTS  Co. — Cheverie,  oxide  of  manganese  (in  limestone) ;  Petite  River,  gypsum,  oxide  of 
manganese  ;  Windsor,  calcite,  cryptomorphite  (boronatrocalcite) ,  howlite,  glauber  salt.  The 
last  three  minerals  are  found  in  beds  of  gypsum. 

KINGS  Co. — Black  Rock,  centrallassifce,  cerinite  ;  cyanolite  ;  a  few  miles  east  of  Black 
Rock,  prehnite  ?  stilbite  !  ;  Cape  Blomidon,  on  the  coast  between  the  cape  and  Cape  Split, 
the  following  minerals  occur  in  many  places  (some  of  the  best  localities  are  nearly  opposite 
Cape  Sharp):  analcite!  !  agate,  amethyst!  apophyllite!  calcite,  chalcedony,  chabazite,  gme- 
linite  (ledererite),  hematite,  heulandite !  laumontite,  magnetite,  malachite,  mexo'ite,  native 
copper  (rare),  natrolite !  psilomelane,  stilbite  !  thomsonite,  faroelite,  quartz;  North  Moun- 
tains, amethyst,  bloodstone  (rare),  ferruginous  quartz,  mesolite  (in  soil)  ;  Long  Point,  five 
miles  west  of  Black  Rock,  heulandite,  laumontite!  !  stilbite  !  !  ;  Morden,  apophyllite,  raor- 
denite  ;  Scot's  Bay,  agate,  amethyst,  chalcedony,  mesolite,  natrolite  ;  Woodworth's  Cove,  a 
few  miles  west  of  Scot's  Bay,  agate  !  chalcedony  !  jasper. 

LUNENBURG  Co. — Chester,  Gold  River,  gold  in  quart/,  pyrite,  mispickel ;  Cape  la  Have, 
pyrite  ;  The  "  Ovens,"  gold,  pyrite,  arsenopyrite  ;  Petite  River,  gold  in  slate. 

PiCTOU  Co. — Pictou,  jet,  oxide  of  manganese,  limonite  ;  at  Roder's  Hill,  six  miles  west  of 
Pictou,  barite ;  on  Carribou  River,  gray  copper  and  malachite  in  lignite ;  at  Albion  mines, 
coal,  limonite  ;  East  River,  limonite. 

QUEENS  Co. — Westfield,  gold  in  quartz,  pyrite,  arsenopyrite ;  Five  Rivers,  near  Big  Fall, 
gold  in  quartz,  pyrite,  arsenopyrite,  limonite. 

RICHMOND  Co. — West  of  Plaister  Cove,  barite  and  calcite  in  sandstone  ;  nearer  the  Cove, 
calcite,  flu&rite  (blue),  siderite. 

SHELBUKNE  Co. — Shelburne,  near  mouth  of  harbor,  garnets  (in  gneiss);  near  the  town, 
rose  quartz  ;  at  Jordan  and  Sable  River,  staurolite  (abundant),  schiller  spar. 

SYDNEY  Co. — Hills  east  of  Lochaber  Lake,  pyrite,  chalcopyrite,  sideride,  hematite  ;  Mor- 
ristown,  epidote  in  trap,  gypsum. 

YARMOUTH  Co. — Cream  Pot,  above  Cranberry  Hill,  gold  in  quartz,  pyrite ;  Cat  Rock, 
Fouchu  Point,  asbestus,  calcite. 

NEWFOUNDLAND. 

ANTONY'S  ISLAND. — Pyrite. 

CATALINA  HARBOR. — On  the  shore,  pyrite  ! 

CHALKY  HILL. — Feldspar. 

COPPER  ISLAND,  one  of  the  Wadham  group. — Chalcopyrite. 

CONCEPTION  BAY. — On  the  shore  south  of  Brigus,  bornite  and  gray  copper  in  trap. 

BAY  OF  ISLANDS. — Southern  shore,  pyrite  in  slate. 

LAWN. — Oalenite,  cerargyrite,  proustite,  argentite. 

PLACENTIA  BAY. — At  La  Manche,  two  miles  eastward  of  Little  Southern  Harbor,  gnlenite!  ; 
on  the  opposite  side  of  the  isthmus  from  Placentia  Bay,  barite,  in  a  large  vein,  occasionally 
accompanied  by  chalcopyrite. 

SHOAL  BAY. — South  of  St.  John's,  chalcopyrite. 

TRINITY  BAY. — Western  extremity,  barite. 

HARBOR  GREAT  ST.  LAWRENCE. — West  side,  fluoride,  galenite. 


GENERAL  INDEX. 


Acadialite,  322. 
Acanthite,  217. 
Achrematlte,  363. 
Achroite,  308. 
Acmite,  272. 
Actinolite,  275. 
Adamine,  Adamite,  351. 
Adelpholite,  341. 
Adular,  Adularia,  303. 
^girine,  ^gyrite,  272. 
Aerinite,  328. 
./Eschynite,  340. 
Agalmatolite,  327,  330. 
Agaric  mineral,  378. 
Agate,  264. 
Agricolite,  280. 
Aikmite,  232. 
Akanthit,  v.  Acanthite. 
Akmit,  v.  Acmite. 
Alabandite,  215. 
Alabaster,  371. 
Alalite,  271. 
Alaun,  v.  Alum. 
Alaunstein,  374. 
Albertite,  394. 
Albite,  301. 
Alexandrite,  253. 
Algodonite,  213. 
Alipite.  329. 
Allanite,  286. 
Allemontite,  205. 
Allochroite,  ®.  Andradite. 
Alloclasite,  226. 
Allophane,  319. 
Allophite,  334. 
Almandin,  Almandite,  281, 
Alstonite,  v.  Bromlite. 
Altaite,  215. 
Alum.  Native,  373. 
Aluminite,  373. 
Alunite,  374. 
Alunogen,  373. 
Amalgam,  203. 
Amazonstone,  303. 
Amber,  393. 
Amblystegite,  268. 
Amblygonite,  347. 
Ambrite,  393. 
Ainbrosine,  393. 
Amethyst,  264. 
Amianthus,  275,  328. 


Amphibole,  274. 
Analcite,  Analcime,  321. 
Anatase,  255. 
Andalusite,  309. 
Andesine,  Andesite,  300. 
Andradite,  282. 
Andrewsite,  356. 
Anglesite,  367. 
Anhydrite,  367. 
Ankerite,  380. 
Annabergite,  350. 
Annite,  291. 
Anorthite,  299. 
Antholite,  v.  Anthophyllite. 
Anthophyllite,  273. 
Anthracite,  395. 
Anthracoxenite,  393. 
Antigorite,  329. 
Antillite,  329. 
Antimonblende,  262. 
Antimonbluthe,  v.  Valentinite. 
Antimonglanz,  210. 
Antimonite,  210. 
Antimonsilber,  212. 
Antimony,  Native,  204. 
Antimony  Glance,  210. 
Apatite,  342. 

Aphanesite  v.  Clinoclasite. 
Aphrite,  Aphrizite,  308,  378. 
Aphrodite,  327. 
Aphrosiderite,  334. 
Aphthalose,  Aphthitalite,  368. 
Apjohnite,  373. 
Aplome,  282. 
Apophyllite,  318. 
Aquacrepitite,  329. 
Aquamarine,  277. 
Aragonite,  383. 
Aragotite,  392. 
Arcanite,  368. 
Ardennite,  288. 
Arfvedsonite,  276. 
Argentine,  378. 
Argentite,  213. 
Arite,  221. 
Arkansite,  256. 
Arksutite,  243. 
Arquerite,  203. 
Arragonite,  383. 
Arseneisen,  v.  Leucopyrite. 
Arseneisensinter,  v.  Pitticite. 


Arsenic,  Native,  204. 
Arsenical  Antimony,  205. 
Arsenikkies,  225. 
Arsenikkupfer,  212. 
Arsennickelglanz,  224. 
Arseniosiderite,  356. 
Arsenite,  v.  Arsenolite. 
Arsenolite,  262. 
Arsenopyrite,  225. 
Asbestus,  275. 

Blue,  v.  Crocidolite. 
Asbolan,  Asbolite,  261. 
Asmanite,  266. 
Asparagus-stone,  343. 
Aspasiolite,  331. 
Asphaltum,  394. 
Aspidolite,  290. 
Astrakanite,  v.  Blodite. 
Astrophyllite,  291. 
Atacamite,  239. 
Atelestite,  356. 
Atelite,  240. 
Augite,  271. 
Aurichalcite,  388. 
Auriferous  pyrite,  199. 
Auripigmentum,  210. 
Automoiite,  250. 
Autunite,  357, 
Aventurine  quartz,  264. 

feldspar,  301. 302,  303. 
Axinite,  288. 
Azorite,  337. 
Azurite,  389. 

Babingtonite,  273. 
Bagrationite,  v.  Allanite. 
Baikalite,  v.  Sahlite. 
Barnhardtite,  223. 
Barite,  365. 
Bartholomite,  373. 
Baryt,  Barytes,  365. 
Barytocalcite,  386. 
Barytocelestite,  366. 
Basanite,  265. 
Bastite,  329. 
Bastnasite,  386. 
Bathvillite,  393. 
Batrachite,  278. 
Beaumontite,  325. 
Beauxite,  259. 
Bechilite,  360. 


478 


INDEX. 


Beilstein,  v.  Nephrite. 

Belonite,  110. 

Benzole,  392. 

Beraunite,  v.  Vivianite. 

Bergholz,  275. 

Bergkrystall,  v.  Quartz. 

Bergmehl,  379. 

Berg-milch,  378. 

Berg-61,  391. 

Bergpech,  394. 

Bergseife,  v.  Halloysite. 

Bergtheer,  v.  Pittasphalt. 

Bernstein,  393. 

Beryl,  277. 

Berthierite,  229. 

Berzelianite,  215. 

Beyrichite,  219. 

Bieberite,  373. 

Biharite,  331. 

Bimsstein,  D.  Pumice. 

Bindheimite.  357. 

Binnite,  229';    228. 

Biotite,  290. 

Bismite,  262. 

Bismuth,  205. 

Bismuth  glance,  210. 

Bismuthinite,  210. 

Bismutite,  390. 

Bismutoferrite,  280. 

Bittersalz,  372. 

Bitter    spar,    Bitterspath,    v. 

Dolomite. 
Bitumen,  394. 
Bituminous  coal,  395. 
Black  jack,  215. 
Blattererz,   Blattertellur,  227. 
Blatterzeolith,  v.   Heulandite. 
Blaueisenerz,  v.  Vivianite. 
Blaueisenstein,  v.  Crocidolite. 
Blauspath,  353. 
Blei,  Gediegen,  204. 
Bleiglanz,  213. 
Bleigliitte,  245. 
Bleigumme,    v.    Plumbogum- 

mite. 

Bleilasur,  374. 
Bleihoruerz,  386. 
Bleiuicre,  357. 
Bleinierite,  v.  Bindheimite. 
Bleispath,  385. 
Bleivitriol,  367. 
Blende.  215. 
Blcdite,  372. 
Bloodstone,  264. 
Blue  Vitriol,  372. 
Bodenite,  286. 
Bog-butter,  393. 
Boy  iron  ore,  259. 

manganese,  261. 
Bole,  Bolus  =  Halloysite. 
Boltonite,  278. 
Bombiccite,  393. 
Boracite,  359. 
Borax,  359. 
Bordosite,  245. 


Bornite,  215. 
Borocalcite,  360. 
Boronatrocalcite,  359. 
Bort,  207. 
Bosjemanite,  373. 
Botallackite,  v.  Atacamite. 
Botryogen,  373. 
Botryolite,  313. 
Boulangerite,  232. 
Bournonite,  231. 
Boussingaultite,  370. 
Bowenite,  275,  328. 
Bragite,  340. 
Branderz,  v.  Idrialite. 
Brandisite,  336. 
Brauneisenstein,  258. 
Braunite,  255. 
Braunkohle,  396. 
Braunspath,  379. 
Bredbergite,  282. 
Breislakite,  «.  Pyroxene. 
Breithauptite,  221. 
Breunerite,  380. 
Brewsterite,  325. 
Brittle  silver  ore,  ».  Stephanite. 
Brochantite.  374. 
Bromargyrite,  238. 
Bromlite',  384. 
Bromsilber,  238. 
Bromyrite,  238. 
Brogniardite,  230. 
Brongnartine,  375. 
Bronzite,  268. 
Brookite,  255. 
Brown  coal,  396. 

iron  ore,  258. 

spar,  379,  380. 
Brucite,  259. 
Brushite,  349. 
Bucholzite,  309. 
Bucklandite,  286. 
Bunsenite,  245. 
Buntkupfererz,  215. 
Bustamite,  272. 
Butyrellite.  393. 
Byerite,  395. 
Bytownite,  299. 

Cacholong,  267. 
Caooxenite,  Cacoxene,  356. 
Cairngorm  stone,  264. 
Calaite,  v.  Callaite. 
Calamine,  317 ;  382. 
Calaverite,  227. 
Calcareous  spar,  tufa,  376.  378. 
Calcite,  376. 
Calcozincite,  245. 
Calc-sinter.  378. 
Caledonite,'  369. 
Callais,  Callaite,  355. 
Calomel,  238. 
Campylite,  345. 
Canaanite  =  White  Pyroxene. 
Cancrinite,  295. 
Cannel  Coal,  395. 


Capillary  pyrites,  219. 

Caporcianite,  316. 

Carbonado,  207. 

Carbon  diamantaire,  207. 

Carnallire,  239. 

Carnelian,  264. 

Carpholite,  319. 

Cassiterite,  253. 

Castor,  Castorite,  273. 

Catapleiite,  317. 

Cataspilite,  331. 

Cat's-eye,  264. 

Cavolinite,  294. 

Celadonite,  327. 

C  lestite,  Celestine,  366. 

Centrallasite,  316. 

Cerargyrite,  238. 

Cerbolite,  370. 

Cerine,  286. 

Cerite,  318. 

Cerolite,  329. 

Cerussite,  385. 

Cervantite,  262. 

Ceylanite,  Ceylonite,  249. 

Chabazite,  322. 

Chalcanthite,  372. 

Chalcedony,  264. 

Chalcocite,  217. 

Chalcodite,  328. 

Chalcolite,  356. 

Chalcomorphite,  319. 

Chalcophanite,  261. 

Chalcophyllite,  353. 

Chalcopyrite,  222. 

Chalcosiderite,  356. 

Cbalcosine,  217. 

Chalcostibite,  228. 

Chalcotrichite,  244. 

Chalk,  378. 

ChaJybite,  381. 

Chathamite,  224. 

Chert,  265. 

Chesterlite,  304. 

Cbessy  Copper, Chessylite,  390. 

Chiastolite,  309. 

Childrenite,  355. 

Chiolite,  242. 

Chladnite,  268. 

Chloanthite,  223. 

Chloralluminite,  238. 

Chlor-apatite,  343. 

Chlorastrolite,  318. 

Chlorite  Group,  333. 

Ghloritoid,  336. 

Chlorif  spath,  336. 

Chlormagnesite,  238. 
I  Chlorocalcite,  238. 
i  Chloropal,  328. 

Chlorophffiite,  334. 

Chlorophane,  241. 

Chlorophyllite,  331. 

Chlorothionite,  238. 

Chlorotile,  351. 

Chodneffite  242. 

Chondrarsenite,  350. 


INDEX. 


4T9 


Chondrodite,  305. 
Chonicrite,  333. 
Chr'smatite,  391. 
Chromeisenstein,  252. 
Chromglimmer,  v.  Fuchsite. 
Chromic  iron,  252. 
Chromite,  252. 
Chrompicotite,  252. 
Chry  sober  pi,  252. 
Chrysocolla,  316. 
Chrysolite,  278. 
Chrysoprase,  264. 
Chrysotile,  328. 
Churchite,  349. 
Cinnabar,  218. 
Cinnamon  stone,  281. 
Clarite,  230. 
Claudetite,  262. 
Ciausthalite,  214. 
Clay,  329,  et  seq. 
Cleavelandite,  302.  , 

Cling-manite.  336. 
Clinoclase.  Clinoclasite,  352. 
Clinochlore,  334. 
Cliuohumite,  306. 
Clintonite,  336. 
Clianthite,  224. 
Coal,  Mineral,  395. 

Bog-head,  396. 

Brown,  396. 

Camiel,  395. 
Cobalt  bloom,  350. 
Cobalt  glance,  224. 
Cobaltine,  Cobaltite,  224. 
Coccolite.  271. 
Coke,  395. 

Colestine,  v.  Celeatite. 
Coeruleolactibe,  354. 
Collyrite,  319. 
Colophonite,  282. 
Columbite,  338. 
Coxnptonite,  320. 
Connellite,  369. 
Cookeite,  332. 
Copal,  Fossil.  393. 
Copaline,  Copalite,  393. 
Copiapite,  373. 
Copper,  Native,  203. 
Copper  glance,  217. 
Copper  mica,  353. 
Copper  nickel,  220. 
Copper  pyrites,  222. 
Copper-vitriol,  v.  Chalcanthite. 
Copperas,  372. 
Coprolites,  344. 
Coquimbite,  373. 
Cordierite,  289. 
Cornwallite,  352. 
Corundellite,  336. 
Corundophilite,  336. 
Corundum,  245,. 
Corynite,  225. 
Cosalite,  230. 
Cossaite,  332. 
Cotunnite,  239. 


Covelline,  Covellite,  227. 
Crednerite.  256. 
Crichtonite,  248. 
Crocidolite,  276. 
Crocoite,  Crocoisite,  363. 
Cronstedtite,  335. 
Crookesite,  213. 
Cryolite,  242. 
Cryophyllite,  293. 
Cryptohalite,  242. 
Cryptolite,  342. 
Cryptomorphite,  360. 
Cuban,  Cubanite,  223. 
Culsageeite,  333. 
Cummingtonite,  275. 
Cuprocalcite,  389. 
Cuprite,  244. 
Cupromagnesite,  373. 
Cuproscheelite,  362. 
Cuprotungstite,  362. 
Cyanite,  310. 
Cyanochalcite,  317. 
Cyanotrichite,  375. 
Cymatolite,  327. 

Damourite,  331. 
Danaite,  226. 
Danalite,  280. 
Danburite,  289. 
Datholite,  Datolite,  312. 
Daubreelite,  220. 
Daubreite,  240. 
Davidsonite,  277. 
Davyne,  Daviua,  294. 
Dawsonite,  388. 
Dechenite,  345. 
Degeroite,  332. 
Delessite,  334. 
Delvauxite,  v.  Dufrenite. 
Demidoffite,  317. 
Derbyshire  spar,  «.  Fluorite. 
Descloizite,  345. 
Desmine,  324. 
Dewalquite,  288. 
Deweylite,  329. 
Diabantachronnyn,  333. 
Diabantite,  333. 
Diaclasite,  269. 
Diadochite,  357. 
Diallage,  Green,  271. 
Diallogite,  Dialogite,  381. 
Diamond,  206. 
Dianite,  v.  Columbite. 
Diaphorite,  230. 
Diaspore,  257. 
Dichroite,  289. 
Dihydrite,  352. 
Dimorphite,  210. 
Dinite,  392. 
Diopside,  271. 
Dioptase,  279. 
Dipyre,  294. 

Discrasite,  v.  Dyscrasite. 
Disterrite  =  Brandisite. 
Disthene,  310. 


Ditroyte,  295. 
Dog-Tooth  Spar,  378. 
Dolerophanite,  368. 
Dolomite,  379. 
Domeykite,  212. 
Doppelspath,  377. 
Dopplerite,  393. 
Dreelite,  368. 
Dry-bone,  382. 
Dudleyite,  336. 
Dufrenite,  356. 
Dufrenoysite,  229. 
Durangite,  348. 
Duxite,  393. 
Dyscrasite,  212. 
Dysluite,  250. 
Dysodile,  393. 
Dysyntribite,  331. 

Earthy  Cobalt,  261. 
Edenite,  275. 
Edingtonite,  319. 
Edwardsite,  V.  Monazite. 
Ehlite,  352. 
Eisenbliithe,  383. 
Eisenglanz,  246. 
Eisenglimmer,  247. 
Eisenkies,  221. 
Eisenkiesel,  v.  Quartz. 
Eisenrose,  247. 
Eisensinter,  v.  Pitticite. 
Eisenspath,  381. 
Eisspath,  304. 
Ekebergite,  294. 
Ekmannite,  332. 
Elaeolite,  294. 
Elaterite,  392. 
Electrurn,  199. 
Embolite,  238. 
Embrithite,  v.  Boulangerite. 
Emerald,  277. 
Emerald  nickel,  388. 
Emery,  246. 
Emplectite,  228. 
Enargite,  235. 
Enceladite,  n.  Warwickite. 
Enstatite,  288. 
Enysite,  375. 
Eosite,  363. 
Ephesite,  332. 
Epiboulangerite,  232. 
Epidote,  285. 
Epigenite.  236. 
Epistiibite,  325. 
Epsom  Salt,  Epsomite,  372. 
Erbsenstein,  378. 
Erdkobalt,  261. 
Erdol,  394. 
Erdpech,  394. 
Eremite,  v.  Monazite. 
Erinite,.352. 
Erubescite,  215. 
Erythrite,  350. 
Erythrosiderite,  239. 
Esmarkite,  331. 


4SO 


INDEX. 


Essonite,  282. 
Ettringite,  373. 
Eucairite,  213. 
Euchroite,  351. 
Euclase,  311. 
Eucolite,  277. 
Eudialyte,  Eudyalite,  277. 
Eudnophite,  322. 
Eugenglanz,  v.  Polybasite. 
Eukairite,  v.  Eucairite. 
Euklas,  311. 
Eulytine,  Eulytite,  280. 
Eumanite,  256. 
Euosmite,  393. 
Euphyllite,  33 '3. 
Euxenite,  340. 

Fahlerz,  233. 

Fahlunite,  331. 

Famatinite,  236. 

Faserquartz,  276. 

Fassaite,  271. 

Faujasite,  322. 

Fauserite,  372. 

Fayalite,  278. 

Feather  ore,  229. 

Federerz,  229. 

Feitsui,  287. 

Feldspar  Group,  297. 

Felsite,  301,  304. 

Feldspath,  v.  Feldspar. 

Fergusonite,  340. 

Ferroilmenite,  338. 

Feuerblende,  230. 

Feuerstein,  265. 

Fibroierrite,  373. 

Fibrolite,  309. 

Fichtelite,  392. 

Fiorite,  267. 

Fireblende,  230. 

Flint,  265. 

Float-stone,  267. 

Flos  feri,  383. 

Fluellite,  242. 

Fluocerite,  242. 

Fluor-apatite,  343.( 

Fluor,  Fluorite,  24*1. 

Fluor  Spar,  241. 

Flussspath,  241. 

Foliated  tellurium,  v.  Nagya- 

gite. 

Fontainebleau  limestone,  378. 
Foresite,  325. 
Forsterite,  278. 
Fowlerite,  272. 
Francolite,  343. 
Franklinite,  251. 
.  Freibergite,  233. 
Freieslebenite,  230. 
Frenzelite,  211. 
Friedelite,  280. 
Fuchsite,  292. 

Gadolin,  Gadolinite,  287. 
Gahnite,  250. 


Galena,  Galenite,  213. 
Galmei,  317,  382. 
Garnet,  280. 
Garnierite,  329. 
Gastaldite,  276. 
Guanovulite,  370. 
Gay-Lussite,  387. 
Gearksutite,  243. 
Gehlenite,  309. 
Geierite,  v.  Geyerite. 
Gekrosstein,  367. 
Gelbbleierz,  £62. 
Genthite,  329. 
Geocerite.  392. 
Geomyricite,  392. 
Gcocronite,  235. 
Gersdorffite,  224. 
Geyerite,  226. 
Geyserite,  267. 
Gibbsite,  260. 
Gieseckite,  330 ;  295. 
Gigantolite,  331. 
Gilbertite,  331. 
Gillingite,  332. 
Girasol,  267. 

Gismondine,  Gismondite,  319. 
Glanzkobalt,  v.  Cobaltite. 
Glaserite,  v.  Arcanite. 
Glaserz,   Glanzerz,    v.   Argen- 

tite. 

Glauber  salt,  370. 
Glauberite,  369. 
Glaucodot,  226. 
Glaucouite,  327. 
Glaueophane,  276. 
Glimmer,  v.  Mica. 
Globulites,  110. 
Gmelinite,  323. 
Gold,  199. 

Goldtellur,  v.  Sylvanite. 
Goshenite,  277. 
Goslarite,  373. 
Gothite,  258. 
Grahamite,  394. 
Gramrnatite,  275. 
Granat,  280. 
Graphic  tellurium,  226. 
Graphite,  208. 

Graukupfererz,  t>.  Tennantite. 
Gray  antimony,  210. 

copper,  233. 
Greenockite,  220. 
Greenovite,  313. 
Grenat,  v.  Garnet. 
Grochauite,  335. 
Grossularite,  281. 
Grtinauite,  215. 
Griinbleierz,  344. 
Guadalcazarite,  219. 
Guanajuatite,  211. 
Guano,  343. 
Guarinite,  314. 
Giimbelite,  331. 
Guyaquillite,  393 
Gymnite,  329. 


Gyps,  ®.  Gypsum. 
Gypsum,  S70. 
Gyrolite,  316. 

Haarkies,  219;  225. 
Haarsalz,  373. 
Hafnefiordite,  301. 
Hagemannite.  243. 
Haidingerite,  349. 
Halite,  237. 
Hallite,  333. 
Halloysite,  330.. 
Halotrichite,  373. 
Hamartite,  386. 
Harmotome,  324. 
Harrisite,  218. 
Hartite,  392. 

Hatchettite,  Hatchettine,  392. 
Hauerite,  222. 
Hausmannite,  255. 
Haiiyne,  Haiiynite,  296. 
Haydenite,  322. 
Hayfrorite,  313. 
Heavy  spar,  365. 
Hebronite,  348. 
Hedenbergite,  &71. 
Hcdyphane,  345. 
Heliotrope,  264. 
Helvin,  Helvite,  280. 
Hematite,  246. 

Brown,  258. 
Henwoodite,  356. 
Hercynite,  250. 
Herderite,  348. 
Hermannolite.  339. 
Herschelite,  322. 
Hessite,  216. 
Hessonite,  v.  Essonite. 
Heteromorphite,  v.  Jameson- 

ite. 

Heulandite,  325. 
Hexagonite,  276. 
Hielmite,  339. 
Highgate  resin,  393. 
Hisingerite,  332. 
Hoernesite,  349. 
Holzopal,  v.  Wood  Opal. 
Holz-Zinn,  253. 
Honey-stone,  Honigstein,  390. 
Horbachite,  219. 
Hornblende,  274. 
Horn  silver,  238. 
Hornstone,  265. 
Horse-flesh  ore,  «.  Bornite. 
Hortonolite,  278. 
Houghite,  260. 
Hovite,  388. 
Howlite,  360. 
Huantajayite,  237. 
Hiibnerite,  361. 
Ilumboldtine,  390. 
Humboldtilite,  284. 
Humboldtite,  312. 
Humite,  305,  306. 
Hureaulite,  350. 


INDEX. 


481 


Huronite,  331. 

Hyacinth,  282,  283. 
Hyalite,  267. 
Hyalophane,  300. 
Hyalosiderite,  278. 
Hydrargillite,  260. 
Hydrargyrite,  245. 
Hydraulic  limestone,  378. 
Hydrocuprite,  24A. 
Hydrocyanite,  368. 
Hydrodolomite,  888. 
Hydrofiuorite,  242. 
Hydromagnesite,  387. 
Hydro -mica  Group,  331. 
Hydrophite,  329. 
Hydrotalcite,  260. 
Hydrotitanite,  249. 
Hydrozincite,  388. 
Hygrophilite,  331. 
Hypargyrite,  228. 
Hypersthene,  268. 
Hypochlorite,  280. 

Ice  spar,  303. 
Iceland  spar,  377. 
Idocrase,  283. 
Idrialiue,  Idrialite,  392. 
Ihlcite,  373. 
Ilmenite,  247. 
Ilsemannite,  262. 
Ilvaite,  287. 
Indianite,  299. 
Indicolite,  308. 
lodargyrite,  238. 
lodsilber,  238. 
lodyrite,  238. 
lolite,  289. 
Iridosmine,  202. 
Iron,  2C4. 
Iron  pyrites,  221. 

Magnetic,  219. 

White,  225. 

Ironstone,  Clay,  247,  259. 
Iserine,  Iserite,  2481 
Isoclasite,  351. 
Itacolumyte,  207. 
Ivigtite,  332. 
Ixolyte,  392. 

Jacobsite,  250. 
Jade,  Common,  275. 
Jadeite,  387. 
Jamesonite,  229. 
Jargon,  283. 
Jasper,  265. 
Jaulingite,  393. 
Jefferisite,  333. 
Jeffersonite,  271. 
Jenkinsite,  329. 
Jet,  396. 
Johaunite,  375. 
Jollyte,  332. 
Jordanite,  229. 
Joseite,  211. 
Julianite,  234. 

31 


N.  B. — Many  names  spelt 
with  an  initial  K  in  German, 
begin  with  C  in  English. 

Kalait,  355. 
Kaliglimmer,  291. 
Kalinite,  373. 
Kalk-Harrnotome.  •».  Phillips  - 

ite. 

Kalk-uranit,  357. 
Kalkspath,  376. 
Kalk-volborthit,  352. 
Kallait,  355. 
Kaluszite,  372. 
Kiimmererite,  333. 
Kammkies,  225. 
Kaolin,  Kaolinite,  329. 
Karelinite,  262. 
Katzenauge,  264. 
Keatingine,  273. 
Keilhauite,  314. 
Kenngottite,  228. 
Kerargyrite,  238. 
Kermes,  Kermesite,  262. 
Kerolith,  v.  Cerolite. 
Kerrite,  333. 
Kiesel,  v.  Quartz. 
Kieselkupfer,  316. 
Kieselwismuth,  280. 
Kieselzinkerz,  317. 
Kieserite,  372. 
Killinite,  331. 
Kischtimite,  386. 
Kjerulfine,  346. 
Klaprotholite,  229. 
Klinochlor,  334. 
Knebelite,  278. 
Kobaltbliithe,  350. 
Kobaltglanz,  224. 
Kobaltkies,  v.  Linngeite. 
Kobaltnickelkies,  223. 
Kobellite,  232. 
Kochelite,  341. 
Kochsalz,  237. 
Kohle,  i).  Coal. 
Kokkolit,  v.  Coccolite. 
Kongsbergite,  203. 
Konigine,  374. 
Konlite,  392. 
Koppite,  337. 
Korarfveite,  346. 
Kottigite,  350. 
Korund,  v.  Corundum. 
Kotschubeite,  335. 
Koupholite,  318. 
Krantzite,  393. 
Kreittonite,  250. 
Krernersite,  239. 
Krisuvigite,  375. 
Kronkite,  375. 
Kupferantimonglanz,  228. 
Kupferbleispath,  374. 
Kupferglanz,  217. 
Kupferglimmer,  353. 
Kupferindig,  227. 


Kupferkies,  222. 
Kupferlasur,  389. 
Kupfernickel,  220. 
Kupfersammterz,  375. 
Kupferschaum,  352. 
Kupferschwarze,  245. 
Kupfferite,  274. 
Kupfer-uranit,  356. 
Kupfer-vitriol,  372. 
Kupferwismuthglanz,  228. 
Kyanite,  310. 

Labradorite,  299. 
Labrador  feldspar,  299. 
Lagonite,  360. 
Lampadite,  261. 
Lanarkite,  369. 
Langite,  375. 
Lanthanite,  388. 
Lapis-lazuli,  296. 
Larderellite,  360. 
Lasurstein,  296. 
Latrobite,  v.  Anorthite. 
Laumonite,  Laumontite,  316. 
Laurite,  225. 
Laxmannite,  364. 
Lazulite,  353. 
Lead,  204. 
Leadhillite,  368. 
Leberkies,  v.  Marcasite. 
Lecontite,  370. 
Ledererite,  323. 
Lederite,  314. 
Lehrbachite,  215. 
Leopoldite,  238. 
Lepidolite,  292. 
Lepidomelane.  291. 
Lesleyite,  332. 
Lettsomite,  375. 
Leucaugite,  271. 
Leuchtenbergite,  335. 
Leucite,  296. 
Leucopetrite,  393. 
Leucophanite,  278. 
Leucopyrite,  226. 
Leviglianite,  219. 
Levyne,  Levynite,  321. 
Lherzolyte,  249. 
Libethenite,  351. 
Liebigite,  390. 
Lievrite,  287. 
Lignite,  396. 
Ligurite,  314. 
Limbachite,  329. 
Limestone,  378,  379. 
Limonite,  258. 
Linarite,  374. 
Linmeite,  223. 
Linsenerz,  352. 
Liroconite,  352. 
Lithionglimmer,  292. 
Lithographic  Stone,  378. 
Lithomarge,  330. 
Livingstonite,  210. 
Loganite,  334. 


482 


INDEX. 


Lollingite,  226. 
Loweite,  372. 
Lowigite,  374. 
Loxoclase,  3C4. 
Ludlamite,  350. 
Ludwigite,  358. 
Liineburgite,  360. 
Luzonite,  236. 
Lydian  stone,  265. 

Made,  309. 
Maconite,  333. 
Magnesioferrite,  251. 
Magnesite,  380. 
Magneteisenstein,  250. 
Magnetic  iron  ore,  250. 
Magnetic  pyrites,  219. 
Magnetite,  250. 
Magnetkies,  219. 
Magnoferrite,  251. 
Malachite,  Blue,  389. 

Green,  389. 
Malacolite,  271. 
Maldonite,  199. 
Malinowskite,  234. 
Manganblende,  t>.  Alabandite. 
Manganepidot,  286. 
Manganglanz,  215. 
Manganite,  258. 
Manganocalcite,  384. 
Manganophyllite,  290. 
Manganspath,  381. 
Marble,  378. 

Verd-antique,  328. 
Marcasite,  225. 
Margarite,  335.. 
Margarites,  11$. 
Margarodite,  331 ;  292. 
Margarophyllites,  326,  et  seq. 
Marialite,  294. 
Marionite,  388. 
Mannatite,  216. 
Marmolite,  328. 
Martibe,  247. 

Mascagniue,  Mascagnite,  370. 
Maskelynite,  300. 
Masonite,  336. 
Massicot,  245. 
Matlockite,  240. 
Maxite,  369. 
Medjidite,  375. 
Meerschaum,  927. 
Megabasite,  361. 
Meionite,  293. 
Melaconite,  245. 
Melanglanz,  v.  Stephanite. 
Melanite,  282. 
Melanochroite,  364. 
Melanophlogite,  267. 
Melanosiderite,  259. 
Melanterite.  373. 
Melilite,  Melinite,  284. 
Melinophane,  278. 
Meliphanite,  278. 
Mellite,  390. 


Meionite,  227. 
Menaccanite,  247. 
Mendipite,  240. 
Mendozite,  373. 
Meneghinite,  234. 
Mengite,  340. 
Mennige,  255. 
Mercury,  Native,  202. 
Mesitine,  Mesitite,  381. 
Mesolite,  321. 
Mesotype,  320. 
Metabrushite,  349. 
Metacinnabarite,  219. 
Metaxite,  329. 
Meymacite,  262, 
Miargyrite,  227. 
Mica  Group,  289. 
Michaelsonite,  286. 
Microcline,  304. 
Microlite,  337. 
Microphlyllites,  Microplakites 

300. 

Microsommite,  295. 
Middletonite,  393. 
Mikroklin,  v.  Microcline. 
Millerite,  219. 
Mimetene,  Mimetite,  344. 
Mimetese,  Minetesite,  344. 
Mineral  coal,  395. 

oil,  391. 

pitch,  394. 

tar,  891. 
Minium,  255. 
Mirabilite,  370. 
Mispickel,  225. 
Misy,  373. 
Mizzonite,  294. 
Molybdiinglanz,  211. 
Molybdanocker,  262. 
Molybdenite,  211. 
Molybdite,  262. 
Molysite,  239. 
Monazite,  346. 
MoudBtein,  v.  Moonstone. 
Monimolite,  348. 
Monrolite,  310. 
Montanite,  375. 
Montebrasite,  348. 
Vtonticellite,  278. 
Montmartite,  v.  Gypsum. 
Vtontmorillonite,  327. 
Moonstone,  301,  302,  303. 
Morenosite,  373. 
Moroxite,  343. 
Mosandrite,  287. 
Vlottramite,  352. 
\iountain  -cork,  275. 

leather,  275. 
Muromontite,  286. 
Muscovite,  291. 
ytiisenite,  «.  Siegenite. 

^adeleisenerz,  258. 
Sadelerz,  232. 
Sadelzeolith,  320. 


Nadorite,  348. 
Nagyagite,  227. 
Numaqualite,  260. 
Nantokite,  238. 
Naphtha,  391. 
Napthaline,  392. 
Natrolite,  320. 
Natron,  387. 
Natronborocalcite,  359. 
Naumanmte,  213. 
Needle  ore,  ®.  Aikinite. 
Nemalite,  260. 
Neotokite,  332. 
Nepheline,  Nephelite,  294. 
Nephrite,  275.     ,. 
Newjanskite,  202. 
Newportite,  336. 
Niccolite,  220. 

Nickel  glance,  v.  Gersdorffite. 
Nickelarsenikglanz,  224. 
Nickelarsenikkies,  224. 
Nickelbliithe,  350 
Nickelglanz,  ®   Gersdorifite. 
Nickel-Gymnite,  329. 
Nickelkies,  219. 
Nickelsmaragd,  388. 
Niobite,  338. 
Nitre,  357. 
Nitrocalcite,  357. 
Nitroglauberite,  357. 
Nitromagnesite,  357. 
Nohlite,  340. 
Nontronite,  328. 
Nosean,  Nosite,  296. 
Noumeite,  329. 
Nuttalite,  ®.  Wernerite. 

Ochre,  red,  247. 
Octahedrite,  255. 
(Ellacherite,  332. 
Okenite,  316. 
Oldhamite,  213. 
Oligoclase,  301. 
Olivenite,  351. 
Olivine.  278. 
Onyx,  265. 
Oolite,  378. 
Opal,  266. 
Ophiolite,  328,  380. 
Orangite,  318. 
Orpiment,  209. 
Orthite,  286. 
Orthoclase,  303. 
Dsmiridiuin,  202. 
Osteolite,  343. 
Ottrelite,  336. 
Ouvarovite,  282. 
Owenite,  336. 
Ozarkite,  320. 
Ozocerite,  Ozokerit,  392. 

^achnolite,  243. 
Pagodite,  327,  330. 
3aisbergite,  272. 
?alagonite,  331. 


INDEX. 


483 


Palladium,  Native,  202. 
Paraffin,  391. 
Paragonite,  332. 
Parankerite,  380. 
Paranthite,  294. 
Parasite,  ®.  Boracite. 
Parathorite.  318. 
P.irgasite,  275. 
Parisite,  386. 
Parophite,  331. 
Pattersonite,  336. 
Pealite,  267. 

Pearl-mica,  v.  Margarite. 
Pearl-spar,  379. 
Pechkohle,  395. 
Pechopal,  267. 
Pectolite,  315. 
Peganite,  356. 
Pegmatolite,  v.  Orthoclase. 
Pelhamite,  333. 
Pencatite,  388. 
Pennine,  Penninite,  333. 
Percylite,  240. 
Periclase,  Periclasite,  245. 
Peridot,  278  ;  308. 
Pericline,  Periklin,  302. 
Peristerite,  302. 
Perlglimmer,  335. 
Perthite,  304. 
Perofskite,  248. 
Perowskit,  248. 
Petalite,  273. 
Petroleum,  391. 
Petzite,  217. 
Phacolite,  322. 
Pharmacolite,  348. 
Pharmacosiderifce.  354. 
Phenacite,  Phenakit,  279. 
Phillipite,  375. 
Phillipsite,  323. 
Phlogopite,  290. 
Phoenicochroite,  364. 
Pholerite,  330. 
Phosgenite,  386. 
Phosphocerite,  342. 
Phosphochalcibe,  352. 
Phosphochromite,  364. 
Phosphorite,  343. 
Phyllite,  336. 
Physalite,  311. 
Piauzite,  394. 
Pickeringite,  373. 
Piootite,  249. 
Picrolite,  329. 
Picromerite,  372. 
Picropharmacolite,  349. 
Pictite,  314. 
Piedmontite,  286. 
Pihlite,  327. 
Pilinite,  322. 
Pimelite,  329. 
Finite,  330. 
Pisanite,  373. 
Pisolite,  378. 
Pistacite,  Pistazit,  285. 


Pistomesite,  381. 
Pitchblende,  252. 
Pittasphalt,  391. 
Pitticite,  Pittizit,  357. 
Plagioclase,  297. 
Plagionite,  229. 
Plasma,  264. 
Plaster  of  Paris,  371. 
Platinum,  Native,  201. 
Platiniridium,  202. 
Pleonaste,  t>.  Spinel. 
Plumbago,  208. 
Plumallophane,  319. 
Plumbogummite,  355. 
Plurnbostib,  v.  Boulangerite. 
Polianite,  256. 
Pollucite,  Pollux,  277. 
Polyargite,  331. 
Polyargyrite,  235. 
Polybasite,  235. 
Polycrase,  340. 
Polychroilite,  331. 
Poly  halite,  371. 
Polymigiiite,  340. 
Poonahlite,  321. 
Porcellophite,  329. 
Prase,  264. 
Prasine,  352. 
Praseolite,  331. 
Predazzite,  388. 
Pregattite,  332. 
Prehnite,  318. 
Priceite,  360. 
Prochlorite,  335. 
Proidonite,  242. 
Prosopite,  243. 
Protobastite,  268. 
Proustite,  231. 
Prussian  blue,  Native,  350. 
Przibramite,  216,  258. 
Pseudocotunnite,  239. 
Pseudomalachite,  352. 
Pseudophite,  334. 
Psilomelane,  260. 
Psittacinite,  352. 
Pucherite,  345. 
Purple  copper.  215. 
Pycnite,  v.  Topaz. 
Pyrallolite,  326. 
Pyrargillite,  331. 
Pyrargyrite,  230. 
Pyreneite,  282.  „ 
Pyrgoni,  271. 
Pyrite,  221. 
Pyrites,  Arsenical,  225. 

Auriferous,  199. 

Capillary,  219. 

Cockscomb,  225. 

Copper,  222. 

Iron,  221. 

Magnetic,  219. 

Radiated,  225. 

Spear,  225. 

White  iron,  225. 
Pyrochlore,  337. 


Pyrochroite,  260. 
Pyroconite,  243. 
Pyrolusite,  256. 
Pyromorphite,  344. 
Pyrope,  281. 
Pyrophyllite,  327. 
Pyropissite,  392. 
Pyroretinite,  393. 
Pyrosclerite,  333. 
Pyrosmalite,  318. 
Pyrostilpnite,  230. 
Pyroxene,  270. 
Pyrrhite,  337. 
Pyrrhosiderite,  258. 
Pyrrhotite,  219. 

Quartz,  262. 

Quecksilberbranderz,  392. 
Quecksilberhornerz,  238. 
Quicksilver,  202. 

Radelerz,  231. 
Radiated  pyrites,  225. 
Raimondite,  373. 
Ralstonite,  243. 
Ratofkite,  241. 
Rauite,  320. 
Raumite,  331. 
Realgar,  209. 
Red  copper  ore,  244. 

hematite,  247. 

iron  ore,  247. 

ochre,  247. 

silver  ore,  230,  231, 

zinc  ore,  244. 
Refdanskite,  329. 
Remingtonite,  388. 
Rensselaerite,  326. 
Resanite,  317. 
Resin,  Mineral,  393. 
Restormelite.  331. 
Retinalite,  329. 
Retinite,  393. 
Reussinite,  393. 
Rhsetizite,  310. 
Rhagite,  355. 
Rhodochrosite,  381. 
Rhodonite,  272. 
Rhomb-spar,  379. 
Rhyacolite,  304. 
Rionite,  234. 
Ripidolite,  334. 
Rittingerite,  230. 
Rivotite,  348. 
Rock  cork,  v.  Hornblende. 

crystal,  264. 

meal,  379. 

milk,  373. 

salt,  237. 
Roemerite.  373. 
Rcepperite,  278. 
Roesslerite,  349. 
Rogenstein,  378. 
Romeine,  Romeite,  348. 
Roscoelite,  345. 


484 


INDEX. 


Rose  quartz,  264. 
Roselite,  350. 
Rosthornite,  393. 
Rosite,  331. 
Rothbleierz,  363. 
Rotheisenerz,  246. 
Rothgiiltigerz,  230,  231. 
Rothkupfererz,  244. 
Rothnickelkies,  220. 
Rothoffite,  281. 
Rothzinkerz,  244. 
Rubellite,  308. 
Ruby,  Spinel,  Almandine,  249. 

Oriental,  246. 

Ruby -blende,  v.  Pyrargyrite. 
Ruby  silver.  230,  231. 
Rutherfordite,  340. 
Rutile,  254. 
Ryacolite,  v.  Rhyacolite. 

Sahlite,  271. 
Sal  ammoniac,  238. 
Salraiak,  238. 
Salt,  Common,  237. 
Samarskite,  339. 
Sammetblende,  258. 
Sanidin,  303. 
Saponite,  330. 
Sapphire,  246 ;  308. 
Sarcolite,  294. 
Sarcopside,  347. 
Sard,  265. 
Sardonyx,  265. 
Sartorite,  228. 
Sassolite,  Sassolin,  358. 
Satin-spar,  371,  378,  383. 
Saussurite,  287. 
Savite,  v.  Natrolite. 
Scapolite  Group,  293. 
Schaurnspath,  378. 
Scheelite,  362. 
Scheererite,  391. 
Schieferspath,  378. 
Schilfgiaserz,  230. 
Schiller-spar.  329. 
Schirmerite,  229. 
Schmirgel,  246. 
Schorlomite,  315. 
Schraufite,  393. 
Schreibersite,  220. 
Schrifterz,  Schiift-tellur,  226. 
Schrockeringlte,  890. 
Schuppenstein,  293. 
Schwartzembergite,  240. 
Schwarzkupfererz,  245. 
Schwatzise,  233. 
Schwefelkies,  221. 
Schwerspath,  365. 
Scleretinite,  393. 
Scleroclase,  228. 
ftcolecite,  Scolezite,  321. 
Scorodite,  353. 
Seebachite,  322. 
Selenblei,  214. 
Selenite,  371. 


Seleuquecksilber,  215. 
Sellaite,  242. 
Semeline,  313. 
Senarmontite,  262. 
Sepiolite,  327. 
Serpentine,  328. 
Seybertite,  336. 
Shepardite,  220. 
Siderite,  381. 
Siegburgite,  393. 
Siegenite,  223. 
Silaonite,  211. 
Silberamalgam,  203. 
Silberglanz,  213. 
Silberhornerz,  238. 
Silberkupferglanz,  218. 
Silex,  v.  Quartz. 
Silicified  wood,  264. 
Siliceous  sinter,  265.  267. 
Silicoborocalcite,  360. 
Sillimanite,  309. 
Silver,  201. 
Silver  glance,  213. 
Simonyite,  372. 
Sinter,  Siliceous,  265,  267. 
Sismondine,  336. 
Sisserkite,  202. 
Skapolith,  v.  Scapolite. 
Skleroklas,  v.  Sartorite. 
Skolezit,  v.  Scolecite. 
Skutterudite,  224. 
Smaltine,  Smaltite,  223. 
Smaragdite,  275.      • 
Smectite,  327. 
Smithsonite,  382. 
Soapstone,  326. 
Soda  nitre,  359. 
Sodalite,  295. 
Sominite,  204. 
Sonnenstein,  v.  Sunstone. 
Spargelstein,  343. 
Spathic  iron,  381. 
Spathiopyrite,  224. 
Spear  Pyrites,  225. 
Speckstein,  326  ;  330. 
Specular  Iron,  246. 
Speerkies,  225. 
Spessartite,  282. 
Speiskobalt,  223. 
Sphasrosiderite,  381. 
Sphasrostilbite,  324. 
Sphalerite,  215. 
Sphene,  313. 
Spiauterite,  220. 
Spinel,  249. 
Spinthere,  313. 
Spodumene,  273. 
Sprodglaserz,  234. 
Sprudelstein,  383. 
Staff  elite,  v.  Phosphorite. 
Stalactite,  378. 
Stalagmite,  378. 
Stanekite,  393. 
Stannite,  223. 
Staurolite,  Staurotide,  314. 


Steatite,  326. 
Steinkohle,  395. 
Steinmark,  330. 
Steiuol,  391. 
Steinsalz.  237. 
Stephanite,  234. 
Sterlingite,  332. 
Sternbergite,  218. 
Stibioferrite,  348. 
Stibnite,  210. 
Stilbite,  324  ;  325. 
Stilpnomelane.  327. 
Stolzite,  362. 
Strahlerz,  352. 
Strahlkies,  225. 
Strahlstein,  275. 
Strahlzeolith,  v.  Stilbite. 
Strigovite,  335. 
Stromeyerite,  218. 
Strontianite,  384. 
Struvite,  349. 
Stylotvp,  Stylotypite,  232. 
Succinellite,  393. 
Succinite,  392. 
Sulphur,  Native,  206. 
Sunstone,  301,  303. 
Susannite,  369. 
Sussexite,  358. 
Sylranite,  226. 
Sylvine,  Sylvite,  238. 
Syngenite,  372. 
Szaibelyte,  358. 

Tabergite,  334. 
Tabular  i?par,  269. 
Tachhyelrite,  239. 
Tafelspath,  269. 
Tagilite,  351. 
Talc,  326. 
Tallingite,  240. 
Tantalite,  337. 
Tapalpite,  217. 
Tapiolite,  339. 
Tasmanite,  393. 
Tellur,  Gediegen,  205. 
Tellurbismuth,  211. 
Tellurium,  Bismuthic,  211. 

Foliated,  227. 

Graphic,  226. 

Native,  205. 
Tellursilber,  216. 
Tellurwisinuth,  211. 
Tengerite,  388. 
Tennaiitite,  234. 
Tenorite,  245. 
Tephroite,  278. 
Tesseralkies,  224. 
Tetradymite,  211. 
Tetrahelrite,  233. 
Thenardite,  368. 
Thomsenolite.  243. 
Thomsomte,  320. 
Thorite,  318. 
Thulite,  287. 
Thuringite,  336. 


INDEX. 


485 


Tiemannite,  215, 
Tile  ore,  244. 
Tin,  Native,  204. 
Tin  ore,  Tin  Stone,  253. 
Tin  pyrites,  0.  Stannrce. 
Tinkal,  359. 
Titaneisen,  247. 
Titanic  iron,  247. 
Titanite,  313. 
Tiza,  «.  Ulexite. 
Tocornalite,  238. 
Topaz,  310. 

False,  264. 
Topazolite,  282. 
Torbanite.  396,  393. 
Torbernite,  Torberite,  356. 
Tourmaline,  307. 
Travertine,  378. 
Tremolite,  275. 
Trichite,  110. 
Triclasite,  331. 
Tridymite,  266. 
Triphylite,  Triphyline,  347. 
Triplite,  347. 
Tripolite,  267. 
Tritomite,  318. 
Trogerite,  357. 
Troilite,  220. 
Trona,  386. 
Troostite,  279. 
Tscheffkinite,  314. 
Tschermakite,  301. 
Tschermigite,  373. 
Tufa,  Calcareous,  378. 
Tungstite,  262. 
Turg-ite,  257. 
Turmalin,  307. 
Turnerite,  346. 
Turquois,  355. 
Tyrite,  340. 
Tyrolite,  352. 

Ulexite,  359. 
Ullmannite,  225. 
Ultramarine,  296. 
Unionite,  287. 
TJraconise,  Uraconite,  375. 
Uranglimmer,  356,  357. 
Uranin,  Uraninite,  252. 
Uranite,  356,  367. 
Urankalk,  390. 
Uranmica,  356,  357. 
Uranochalcite,  375. 
Uranophane,  319. 
Uranospiuite,  357. 
Uranotantalite,  339. 
Uranotile,  319. 


Uranpecherz,  252. 
Urao,  387. 
Urpethite,  391. 
Uwarowit,  282. 

Vaalite,  333. 
Valentinite,  262. 
Vanadinite,  345. 
Vauqueline,  Vauquelinite,  364. 
Verd- antique,  328. 
Vermiculite,  333. 
Vesuvianite,  283. 
Veszelyite,  351. 
Victorite,  268. 
Villarsite,  318. 
Vitreous  copper,  217. 

silver,  213. 
Vitriol,  Blue,  372. 
Vivianite,  349. 
Voglianite,  375. 
Voglite,  390. 
Volknerite,  260. 
Volborthite,  352. 
Voltaite,  373. 
Vorhauserite,  329. 
Vulpinite,  367. 

Wad,  261. 
Wagnerite,  346. 
Walchowite,  393. 
Walpurgite,  357. 
Wapplerite,  349. 
Warringtonite,  374. 
Warwickite,  360. 
Wavellite,  354. 
Websterite,  v.  Aluminite. 
Wehrlite,  211. 
Weissbleierz,  385. 
Weissite,  331. 
Weisspiessglaserz,  262. 
Wernerite,  294. 
Werthemanite,  374. 
Westanite,  310. 
Wheelerite,  393. 
Wheel-ore,  231. 
Whewellite,  390. 
Whitneyite,  213. 
Wichtine,  Wichtisite,  277. 
Willcoxite,  336. 
Willemite,  279. 
Williamsite,  329. 
Wilsonite,  331. 
Winklerite,  350. 
Winkworthite,  360. 
Wiserine,  255,  342. 
Wismuth,  G-ediegen,  205. 
Wismuthglanz,  210. 


Wismuthocker,  262. 
Wismuthspath,  390. 
Witherite,  384. 
Wittichenite,  232. 
Wocheinite,  259. 
Wohlerite,  278. 
Wolfachite,  225. 
Wolfram,  361. 
Wolframite,  361. 
Wollastonite.  269. 
Wollongongite,  394. 
Wood-opal,  267. 
Wood  Tin,  253. 
Woodwardite,  375. 
Worthite,  310. 
Wulfenite,  362. 
Wiirfelerz,  354. 
Wurtzite,  220. 

Xanthophyllite,  336. 
Xanthosiderite,  259. 
Xenotime,  342. 
Xyloretinite,  393. 

Yenite,  287. 
Yttergranat,  281. 
Ytterspath,  342. 
Yttrocerite,  242. 
Yttrotantalite,  339,  340. 
Yttrotitanite,  314. 

Zaratite,  388. 
Zeolite  Section,  320. 
Zepharovichite,  354. 
Zeunerite,  357. 
Ziegelerz,  244. 
Zietrisikite.  392. 
Zinc,  Native,  204. 
Zinc  blende,  215. 
Zinc  bloom,  «\  Hydrozincite. 
Zinc  ore,  Red,  244. 
Zincite,  244. 
Zinkbliithe,  388. 
Zinkenite,  228. 
Zinkspath,  382. 
Zinnerz,  Zinnstein,  253. 
Zinnkies,  223. 
Zinnober,  218. 
Zinnwaldite,  v.  Lepidolite. 
Zippeite,  375. 
Zircon,  282. 
Zoisite,  286. 
Zoblitzite,  329. 
Zonochlorite,  318. 
Zorgite,  215. 
Zwieselite,  347. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

Return  to  desk  from  which  borrowed. 
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26No/52 
DEC 3    1952  ' 


LD  21-95n*-ll,'50(2877sl6)476 


MAR.  2  4  1960 


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IIVERSITY  OF  CALIFORNIA  LIBRARY 


